Joint Structure & Function-A Comprehensive Analysis Fourth Edition Pamela K.

Copyright © 2005 by F. A. Davis. 528 ■ Section 5: Integrated Function Kinetic Analysis reaction forces (GRFs). GRFs are described by using a A kinetic analysis is performed to understand the forces cartesian coordinate system with forces expressed along acting on the joints, the moments produced by the vertical, anteroposterior, and mediolateral axes.3 The muscles crossing the joints, and the energy require- vector sum of the force components in each direction ments of gait. Most commonly, a link-segment model is is a single expression of the ground reaction force used with an inverse dynamic approach. This means (GRFV), which has a typical pattern from initial contact that we look at the body as a model made up of several to toe-off. In the vertical direction, the magnitudes are parts (segments). We approach the analysis segment by low at first but increase to values that are greater than segment from distal to proximal, using newtonian body weight both in early stance and again in late mechanics. Figure 14-14 shows a simple four-segment stance, with lower values at midstance. These fluctua- gait model (foot, lower leg, thigh, half of HAT) with tions are expressions of the vertical acceleration and one side of the body considered. We must know the deceleration of the body through the stride. In the positions of body markers in motion analysis technol- anteroposterior direction, the GRF is directed posteri- ogy, and we will place these at joint centers. We also orly against the foot that is making initial contact and need to know all of the external forces acting on the prevents the foot from slipping forward. It reaches a body, and for the walking person, these are inertia, maximum magnitude of about 20% of body weight. At gravity, and the GRF.3 The magnitude, direction, and midstance, the force becomes neutral, but as the body point of application of the GRF on the foot is usually enters the second half of stance phase, the vector is determined through the use of a force platform.36 The directed anteriorly against the foot, enabling the per- inertial force is proportional to the acceleration of the son to push off. The mediolateral forces are small in segment. magnitude and are variable across individuals. The use- fulness of the GRFs in understanding gait, particularly Continuing Exploration: Understanding How the in the sagittal plane, is discussed later in the chapter. Kinetics of Gait Are Studied Center of Pressure The three equations on which the solutions are based for a two-dimensional analysis are simple: for The CoP of the foot on the supporting surface moves each segment, the following three are applied: along a path during gait and produces a characteristic pattern (Fig. 14-13). The pattern for normal individuals ⌺Fx ϭ max (1) during barefoot walking differs from the patterns in which various types of footgear are used.35 In barefoot ⌺Fy ϭ may (2) walking, the CoP starts at the posterolateral edge of the heel at the beginning of the stance phase and moves in ⌺M0 ϭ I␣ (3) a nearly linear manner through the midfoot area, remaining lateral to the midline, and then moves medi- where ally across the ball of the foot with a large concentra- ⌺ means “the sum of all of the” tion along the metatarsal break. The CoP then moves to Fx ϭ forces in the designated x direction, in this case second and first toes during terminal stance. horizontal, in newtons (N) ▲ Figure 14-13 ■ A center of pressure (CoP) pathway is shown by the position of the black dot at initial contact (A), at foot flat (B), just before heel-off (C), and just before toe-off (D).

Copyright © 2005 by F. A. Davis. Chapter 14: Gait ■ 529 Fy ϭ forces in the designated y direction, in this case vertical, in N ay ϭ acceleration of the center of mass derived from position and time data, in m/sec2 1/2 Head,arms and trunk M0 ϭ moment about selected point 0, the center of segments: mass, in newton-meters (N·m), largely attributable mass to muscle activity, with ligaments, tendons, joint Moment of inertia location of center of mass capsules, and bony components involved to a Thigh segment: lesser extent mass I ϭ moment of inertia, derived from anthropometric moment of inertia location of center of mass tables, in kg·m2 Lower leg segment: ␣ ϭ angular acceleration of segment derived from mass segment position and time data, in radians per moment of inertia location of center of mass second squared (rad/sec2) Foot segment: If we refer to Figure 14-15 with reference to the mass foot segment, equation (1) says that that the sum of all forces in the x direction (see convention in the figure) moment of inertia must equal the product of the mass of the foot and its location of center of mass acceleration in the x direction. Equation (2) says that the sum of all forces in the y direction (see convention ▲ Figure 14-14 ■ Simple four-segment link segment model of in the figure) must equal the product of the mass of the half a human body for use in gait studies. For each segment identi- foot and its acceleration in the y direction. Equation fied, the mass, moment of inertia, and location of the center of mass (3) says the sum of the moments about any designated should be known for applications. center (we are choosing the center of mass) must equal the product of the moment of inertia (which can be m ϭ mass of the segment, derived from anthropo- visualized as the resistance to rotation) and the angular metric tables, in kilograms (kg) acceleration of the segment. Figure 14-15 shows that there are three things we do not know: the X force at ax ϭ acceleration of the center of mass in the x direc- the ankle (FAX), the Y force at the ankle (FAY), and the tion, derived from position and time data, in moment around the ankle (MA). Foot floor forces are meters per second squared (m/sec2) designated FFX and FFY. There is no moment about free end of the segment. Note that, having three equations, we can solve for only three unknowns and cannot calculate the muscle moments on opposite sides of the joint if there is co- contraction. Applying these three equation results in numbers for the X force at the ankle, the Y force at the Convention Ankle joint FAY MA y Vertical force .05m = y direction .09m Center of mass FAX mg = 9.8 x .82 ay = 5.5 m/s M α = – 47r x = 8.0 N Horizontal force = x direction ax = 9.9 m/s FFY = 530 N Metatarsal head ᭣ Figure 14-15 ■ Free body diagram of the foot segment FFX = 115 N in stance shown with proximal joint (ankle) and all forces and moments acting on the segment. No moment is present at free .04m .08m end of the segment. Known forces and their location are mass of foot and foot-floor force. Unknown forces are joint reaction forces on the ankle and net moment at the ankle joint.

Copyright © 2005 by F. A. Davis. 530 ■ Section 5: Integrated Function Table 14-2 Input Data and Net Moment and Forces Derived from Example Shown in Figure 14–15 Given Information Calculated Information Term Value Term Calculated from Value Body mass 56.7 kg Mass of foot Proportion body mass 0.822 kg Gravitational 9.8 Moment of Proportion segment length, 0.0026 kg/m2 constant 9.9 m/s inertia radius of gyration Ϫ107 N Center of mass: 5.5 m/s Force at ͚F ϭ max Fax ϩ 115 ϭ m(9.9) acceleration x 115 N (to right) ankle: Fax acceleration y 530 N (upward) ͚F ϭ may Ϫ517 N Foot-floor force: Force at Fayϩ530Ϫ0.822(9.8) ϭ m Ϫ78.7 N x direction ankle: Fay y direction (9.9) Moment at ͚M ϭ I␣ ankle Maϩ (107)(0.05) ϩ (517)(0.04) ϩ 115(0.09) ϩ 530(0.08) ϭ .0026(Ϫ47.15) Data from Winter DA: Biomechanics and Motor Control of Human Movement, 2nd ed. New York, John Wiley & Sons, 1990. Calculations performed about center of mass of foot. ankle, and the moment at the ankle (Table 14-2). In ■ Sagittal Plane Moments other words, we are finding out what forces and moments had to have been acting at the ankle in order that the foot with that The sagittal plane joint angles described previously particular mass and moment of inertia move with those par- yield the moment profiles for the hip, knee, and ankle ticular linear and angular accelerations. Now we simply (Fig. 14-16). progress up the body segment by segment and solve for the more proximal joint. Larger numbers of segments Before examining the details of joint moments, let and three-dimensional analyses are more complex than us consider the concept of the support moment. An this, but the principles are the same. examination of the moments acting at the lower extremity show that for most of stance phase, the alge- Internal and External Forces, braic sum of all internal moments acting at the hip, Moments, and Conventions knee, and ankle is a positive or extensor internal moment (Fig. 14-17). Winter7 called this quantification Internal moments are moments generated by the mus- of the total limb synergy a support moment, and he cles, joint capsules, and ligaments to counteract the found the extensor support moment to be consistent external forces acting on the body. External forces such for all walking speeds for both normal individuals as the GRF produce external moments about the joints. and persons with disabilities. The internal extensor For example, when the weight is on the forefoot in late moment keeps the leg from collapsing during the stance phase, an internal ankle plantarflexor moment stance phase. Because hip and knee moments may vary produced by the calf muscle will oppose the external considerably among individuals as long as the net dorsiflexion moment caused by the GRF and other moment remains an internal extensor moment, the external forces that are tending to dorsiflex the foot. body can vary how it accomplishes its support. If ankle Although some academicians use the external moment plantarflexors are deficient, the hip extensors and/or convention, we are going to use the internal moment the knee extensors can compensate. If contraction of convention in this chapter. The word “internal” will be the knee extensors causes pain, the hip extensor used frequently for ease of reading. and/or ankle plantarflexors can compensate. The sup- port moment changes from a net internal extensor to a ■ Moment Conventions net internal flexor moment in late stance (55% to 60% of the gait cycle) that continues into swing. In late Different authors use different conventions to display swing, a net internal extensor moment appears again, internal moments on figures, but they usually indicate presumably to assist in the final positioning of the limb the direction of the moment by the words “flexor/ for heel contact.7,37 extensor,” “abductor/adductor,” or “internal/external rotator.” The moment profiles presented here display The support moment provides a backdrop to the following internal moments as positive: ankle plan- understand the joint moment profiles for each joint. In tarflexor, knee extensor, and hip extensor. Figure 14-16, observe that hip extension provides all of the positive moment in early stance, but it is soon joined by an internal knee extensor moment. Remember that the moment identifies only the poten- tial of the muscle group to support; it does not mean

Copyright © 2005 by F. A. Davis. Chapter 14: Gait ■ 531 Internal Moments SAGITTAL PLANE GRFV GRFV GRFV Extensor Extensor Flexor moment moment moment Extensor Flexor moment moment Flexor Dorsiflexor Dorsiflexor moment moment moment Plantar flexor moment CoP CoP CoP A Initial contact Foot flat Midstance GRFV GRFV GRFV Flexor Flexor moment moment Flexor moment Flexor Flexor Extensor moment moment moment Plantar Plantar Flexor Plantar Flexor flexor flexor moment flexor moment moment moment CoP (toes) moment (toes) CoP Heel off CoP Toe off B Midstance extensor HIP extensor KNEE plant ANKLE Sagittal N.m/kg Joint Moment N.m/kg 0.75 N.m/kg 1.75 0.50 dorsi 1.25 flexor 1.25 flexor 0.25 0.75 0.00 0.50 0.75 -0.25 0.25 -0.25 -0.75 -1.25 20 40 60 80 100 -0.50 20 40 60 80 100 0.25 20 40 60 80 100 0 % Gait Cycle 0 % Gait Cycle 0 % Gait Cycle C ▲ Figure 14-16 ■ Patterns of internal moments in the sagittal plane at the hip, knee, and ankle with center of pressure (CoP) and ground reaction force vectors (GRFVs). The dotted lines represent the standard deviations, and the solid lines represent the mean values. (Diagrams of internal moments redrawn from Winter DA, Eng JJ, Isshac MG: A review of kinetic parameters in human walking. In Craik RL, Otis CA [eds]: Gait Analysis: Theory and Application, pp 263-265. St. Louis, Mosby–Year Book, 1994, with permission from Elsevier.)

Copyright © 2005 by F. A. Davis. 532 ■ Section 5: Integrated Function Moment of Force-Natural Cadence (N = 19) 2 Moment / Bodymass (N.m / KG ) 1 SUPPORT CV = 53% PLANTAR EXT EXT EXT 0 1 HIP CV = 140% 0 -1 Text/im1age rights not avKNaEEilable. CV = 135% 0 -2 2 1 ANKLE CV = 42% 0 ᭣ Figure 14-17 ■ Typical pattern of sagittal plane TOE OFF = 60% moments at the hip, knee, and ankle, shown with their algebraic sum, the support moment. (Redrawn from 0 Winter DA: The Biomechanics and Motor Control of 20 40 Human Gait: Normal, Elderly and Pathological, 2nd ed. 60 80 Waterloo, Ontario, Waterloo Biomechanics, 1991, with 100 permission from David A. Winter.) % of stride that muscle shortening or lengthening is occurring. If, ■ Transverse Plane Moments for example, the net internal moment is caused by the knee extensors, the knee may be flexing (eccentric Transverse plane internal moments tend to be small at contraction) or extending (concentric contraction) or each of the hip, knee, and ankle joints and follow simi- remaining unchanged (isometric contraction). There lar shapes. is increasing support by the ankle plantarflexors as stance phase proceeds until they become the only sup- C a s e A p p l i c a t i o n 1 4 - 4 : Difficulty in Developing an port in most of late stance. During swing phase, Adequate Support Moment moments are very small, as would be expected. Ms. Brown has low levels of activation of her ankle plan- ■ Frontal Plane Moments tarflexors, knee extensors, and, to a lesser extent, hip extensors. This will make it difficult for her to develop an Large internal abduction moments of similar shapes adequate support moment. This is no doubt the reason occur at the hip and knee, and a smaller one occurs at that she thrusts her knee backward to gain knee stabil- the ankle. These are provided largely by ligament ity. We know that she has smaller deficits at the hip than forces across the knee and ankle joints and are neces- at the ankle, and so we would encourage hip extension sary, inasmuch as the center of mass of the body is con- in early stance to assist with the support moment, as siderably medial to the point of support on the foot. well as trying to stimulate the knee extensors. During There appears to be some active component at the this early poststroke period, we would expect some nat- knee, however (either muscular or passive spring ural increase in force-generating capability of the mus- related), inasmuch as some power generation is evident cles and be prepared to take advantage of it by in Figure 14-18.

HIP INTERN FRON Frontal Joint Moment KNEE (N.m/kg) 1.50 (N.m/kg) 0.95 adductor abductor 1.25 adductor abductor 0.75 1.00 0.55 0.75 20 40 60 80 100 0.35 20 0.50 0.15 %G 0.25 -0.05 0.00 -0.25 -0.25 0 0 % Gait Cycle 0.25 Transverse TRANSVERSE PLANE Moment 0.15 N.m/kg 0.15 N.m/kg 0.10 Int. Rot ext. Rot Int. Rot ext. Rot 0.05 0.05 20 40 60 80 100 20 -0.05 0.00 % -0.15 -0.05 -0.25 -0.10 0 -0.15 0 % Gait Cycle 533 ▲ Figure 14-18 ■ Patterns of internal moments in the frontal plane at the hip, knee, and an ues. (Redrawn from Winter DA, Eng JJ, Isshac MG: A review of kinetic parameters in human wal Mosby–Year Book, 1994, with permission from Elsevier.)

NAL MOMENTS NTAL PLANE ANKLE 0.25 (N.m/kg) 0.15 invertor everrtor 0.05 40 60 80 100 -0.05 20 40 60 80 100 0 Gait Cycle % Gait Cycle N.m/kg 0.125 Int. Rot ext. Rot 0.100 0.075 40 60 80 100 0.050 20 40 60 80 100 0.025 0.000 -0.025 0 Gait Cycle % Gait Cycle nkle. The dotted lines represent the standard deviation, and the solid lines indicate the mean val- lking. In Craik RL, Otis CA [eds]: Gait Analysis: Theory and Application, pp 263-265. St. Louis,

Copyright © 2005 by F. A. Davis. 534 ■ Section 5: Integrated Function least amount of energy is necessary to travel a unit of distance. When asked to walk at a comfortable speed, strengthening during functional movements. If over time people choose the speed at which they are most effi- she is unable to provide enough support, an ankle cient, and if the speed of walking increases above this, orthosis would provide a passive extensor moment, but the energy cost per unit of distance walked increases.31 there may be energy costs to doing this. Also as described previously, as the speed of walking decreases below free walking speed, the energy cost Continuing Exploration: Kinematics and Kinetics increases. The probable causes will be apparent when of the Foot and Ankle we examine energy costs from a biomechanical rather than a metabolic perspective. Specific descriptions of the biomechanics of the foot during gait have been hindered by the use of the Mechanical Energy of Walking terms “pronation” (a composite of dorsiflexion, ever- sion, and abduction [external rotation]) and Muscles perform work on the parts of the body in order “supination” (a composite of plantarflexion, inver- that they change their height or change their transla- sion, and adduction [external rotation]). Usually, tional and/or rotational velocity. All energy added to the foot movement is described as consisting of the body by means of concentric muscle contractions pronation early in stance, followed by progressive results in increases in velocity of some part or parts, supination. However, three-dimensional analyses of increases in height, or both. In other words, energy is the lower leg and foot, modeling the foot as a rear- generated and positive work is done on the body. All foot segment and a forefoot segment, have provided energy taken away from the body by means of eccentric more insight into its behavior during stance.38,39 contractions results in decreases in velocity of some Specifically, the rearfoot segment everts with regard part or parts, lowering of the part or parts, or both. to the lower leg early in stance and inverts during Another way of saying this is that energy is absorbed push-off. Three very small net moment torques (not and negative work is done on the body. exceeding 0.10 Nm/kg) are evident in the frontal plane through stance at the ankle until about 20% of There are two common ways of analyzing work and the cycle when an internal evertor moment domi- energy in movement analysis of the human body during nates, followed by an internal invertor moment until gait. The first is usually referred to as the kinematic near 50% of the cycle. Thereafter, until toe-off, an approach. The other is usually referred to as the internal evertor moment dominates. In the trans- mechanical power analysis. Both methods use biome- verse plane, the rearfoot segment externally rotates, chanical models that can be simple or complex, and (abducts) in early stance, followed by smooth inter- both must make a number of simplifying assumptions. nal rotation (adduction) through push-off. The fore- Although these are the most commonly used ap- foot segment adds considerably to dorsiflexion proaches, other investigators have developed models by during early stance and midstance and shows a few using a theoretical dynamical systems perspective,40 degrees of inversion in the frontal plane in early pursuing the notion that motor pattern development in stance, thereafter remaining neutral until push-off, locomotion is driven by the underlying dynamics of the when it once again inverts a few degrees. In the task and the dynamic resources available to the person. transverse plane, the forefoot rotates externally (abducts) a few degrees in early stance and internally Mechanical Energy: rotates (adducts) during push-off. Kinematic Approach Energy Requirements The total energy of a body of several “segments” at a given instant in time is the sum of the potential energy The main objective of locomotion is to move the body and two forms of kinetic energy, translational (linear) through space with the least expenditure of energy. and rotational, of each segment. Translational energy Energy is the capacity to do work, and both work and refers to energy related to the linear velocity of a seg- energy are expressed in the same units, joules (J). Work ment in space. Rotational energy is due to the rota- is performed by the application of force, which pro- tional velocity of a segment in space. Potential energy is duces accelerations and decelerations of the body and the quantity of mass, multiplied by the height to which its segments. Muscles use metabolic energy to perform it is raised. In other words, whenever a mass is raised, mechanical work by converting metabolic energy into gravity tends to act on it and make it fall, and therefore mechanical energy. the mass has potential energy. The amount of potential energy that an elevated mass possesses is equal to the The overall metabolic cost incurred during loco- amount of kinetic energy that was necessary to lift the motion may be measured by assessing the body’s oxy- mass against gravity. When the mass has stopped elevat- gen consumption per unit of distance traveled. If a long ing or is at its peak, kinetic energy is transformed into distance is traveled but only a small amount of oxygen potential energy. When the mass falls, the potential is consumed, the metabolic cost of that particular gait is energy is transformed back into kinetic energy as the low. Oxygen consumption for a person walking at 4 to mass accelerates. 5 km/hour averages 100 mL/kg body weight per minute. The highest efficiency is attained when the

Copyright © 2005 by F. A. Davis. Chapter 14: Gait ■ 535 Segments: For each segment: Head, arms, PE = mgh and trunk KE = 1/2 mv2 + 1/2 Iα2 (HAT) Energy of each segment = Two thighs PE + KE Two lower Total energy of body = legs Sum of energies of all segments Two feet Where: PE = potential energy KE = kinetic energy m = mass of segment g = gravitational constant h = height above ground v = linear velocity I = moment of inertia α = angular acceleration ᭣ Figure 14-19 ■ Seven-segment model illustrating determi- nation of energy at an instant in time, kinematic approach. Figure 14-19 is a model of the segmental energies the gait cycle, respectively, reflects the low position of of a simple 7-segment body, and Figure 14-20 shows the the body at initial contact. At approximately midstance potential and kinetic energy levels of the HAT, and of each foot, the body reaches its highest position, or their sum.41 Rotational kinetic energy is neglected maximum potential energy. Examination of the kinetic because it is very small for the HAT. The low potential energy levels for each instant in time reveals that not energy at initial contact of each foot at 0% and 50% of only is the pattern nearly the “mirror image” of the potential energy but also the magnitudes of the initial contact changes are quite similar. At initial contact, the body 440 has the lowest potential energy but is moving the fastest, and as it moves into midstance, the potential 430 energy rises and is exchanged for kinetic energy. In this way there are great energy savings, as can be seen in the Total top curve, which is the sum of potential and kinetic components. It is also apparent that if kinetic energy energy does not match potential energy in magnitude—that is, if the person walks much more slowly or much more 410 midstance of HAT quickly—conservation would be reduced. Figure 14-21 shows the same total energy curve for the HAT above 400 the total energy curves for each of the two limbs. When the limb curves are added to the HAT curve, 380 yielding the top curve, it is apparent that no energy sav- ings occur between the two limbs and that savings Energy, joulesText/image rights not availaPbotelnetial. between the HAT and the limbs is modest. Further- 360 LOCW 39 energy more, the limbs are larger contributors to the total energy costs than is the HAT. Now it is clear why Total energy of HAT Saunders’ determinants theory is inadequate30: most of the cost of walking is involved in moving the limbs, not Potential energy the trunk, despite the greater mass of the trunk. 50 Kinetic (translational) The segment-by-segment mechanical energy ap- energy proach has given some important insight into the total costs and the patterns of exchange and transfer 40 Kinetic Heat control between and within body segments that occur during energy walking. Note, however, that this analysis does not tell of HAT us which muscle groups produced the energy, which absorbed it, or when these events occurred. For this we 30 need a mechanical power and work analysis. Toe off Toe off 20 0 200 400 600 800 1000 Time, ms ▲ Figure 14-20 ■ Potential and kinetic energy levels of the head, arms, and trunk (HAT) segment, and their sum for one stride in gait.(Redrawn from Winter DA, Quanbury AO, Reimer GD: Analysis of instaneous energy of normal gait. J Biomech 9:253-257, 1976, with permission from Elsevier.)

Copyright © 2005 by F. A. Davis. 536 ■ Section 5: Integrated Function Energy contribution from torso and legs 600 590 Total energy of body from HAT 580 and both legs 440 Total body energy Torso energy Energy, joules Rt. toe offRight leg energy Rt. heat control Rt. toe off Left leg energy 430 Text/image rights not available.TotalenergyofHATfrompotential and kinetic 100 90 Energy from each leg 80 70 200 400 600 800 1000 0 Time, ms ▲ Figure 14-21 ■ Total energy curve shown with that of the HAT and those of the two limbs. (Redrawn from Winter DA, Quanbury AO, Reimer GD: Analysis of instaneous energy of normal gait. J Biomech 9:253-257, 1976, with permission from Elsevier.) Continuing Exploration: Kinematic Approach This statement contains a simplifying assumption to Energy that is satisfactory for simple models: if the energy level of one segment is increasing while another is For simplicity, let us assume that markers are placed decreasing, then energy is being transferred between immediately over joint centers. The only kinetic them. information needed is knowledge of the masses of each segment, and these are usually calculated C a s e A p p l i c a t i o n 1 4 - 5 : Effects of an Ankle- as a percentage of the person’s body weight from Foot Orthosis anthropometric tables.42 The velocities of the cen- ters of mass of the segments are derived from Recall that Ms. Brown hiked up her affected side (lifted position data. The locations of the centers of mass hip and pelvis) in order to clear her foot during swing are determined from anthropometric tables. Note phase. This has been shown to have a serious energy in Figure 14-19 that two constants are needed: g, cost43 as the full weight of the upper body is raised and the gravitational constant of 9.8 m/sec, and I, the lowered, and there are no opportunities for savings by moment of inertia, which is derived from anthro- kinetic-potential exchange. Because the inability to ade- pometric tables. The total energy of the body at quately dorsiflex her foot appeared to be part of the a given instant in time is calculated as the sum problem, a light and, it is hoped, temporary ankle foot of potential and kinetic energy of each of the orthosis was prescribed. This also assisted with her involved parts. The difference between the energy inability to provide sufficient support during stance. She levels for one segment at two successive instants gained the ability to bend her knee in later stance, thus in time is the total energy cost of moving the avoiding excessive hip hiking. Watch for possible draw- segment over that time interval. Note that the net backs while you read the section on power and work. If result may be positive or negative (denoting positive the orthosis does not permit any ankle plantarflexion or negative work). The absolute (positive and nega- during push-off, she will lose the energy that would oth- tive) changes for all segments can be added together erwise be provided by plantarflexor generation. algebraically to give the changes for the whole body.

Copyright © 2005 by F. A. Davis. Mechanical Power and Work Chapter 14: Gait ■ 537 Power (P) profiles across the hip, knee, and ankle are tion (both caused by abductor structures). The ankle compared with joint angle and major muscle activ- power pattern shows minor fluctuations and a small ity profiles in Figures 14-22 to 14-24. P is measured in and somewhat inconsistent absorption burst during watts (W), equivalent to joules per second (J/sec), or push-off. newton-meters per second (Nm/sec).24 Power values are normalized by dividing the power in watts by the In the transverse plane (see Fig. 14-24), the hip subject’s weight in kilograms to make it possible to com- powers are small and somewhat inconsistent, as can be pare across subjects. A summary of the phases of power seen by the large standard deviation of the profiles. The generation and absorption and of the muscle groups power profiles at the knee are also very small, with one responsible during stance phase appear in Table 14-3 consistent negative burst during early stance. This for initial contact to midstance and in Table 14-4 for appears to result from passive structures resisting exter- midstance to toe-off. In the sagittal plane (see Fig. nal rotation of the knee. At the ankle, the power is 14-22), a burst of positive work (energy generation) minuscule and inconsistent. occurs as the hip extensors contract concentrically dur- ing early stance (H1-S), while the knee extensors per- Continuing Exploration: Understanding Power form negative work (energy absorption) by acting and Work in Gait eccentrically (K1-S) to control knee flexion during the same period.31 Negative work is performed by the plan- Examination of power plots helps explain the mus- tarflexors (A1-S) as the leg rotates over the foot during cles responsible for gait and its phases. When slow or the period of stance from foot flat to about 40% of the inefficient gait is a problem, knowledge of the gait cycle. However, a small amount of positive work is sources of power enables a health practitioner to done by the knee extensors at the beginning of this assist the client compensate for deficiencies. Note period (K2-S), extending the knee after foot flat.31 that the scales used for power vary, and this must be Positive work of the plantarflexors at push-off (late taken into account when assessing the work (the stance, ~40% to 60% of the gait cycle) and hip flexors area under the power curve). In Figure 14-22, iden- at pull-off (late stance and in early swing, ~50% to 75% tify the joint around which the largest amount of of the gait cycle) increases the energy level of the body. positive work (above zero line) is performed in the During this 40% to 60% of the gait cycle when energy sagittal plane. It is apparent that the burst denoted is being generated from A2-S and H3-S, simultaneous A2-S (S denoting burst in the sagittal plane) is the absorption is occurring by knee extensors (K3-S). In largest, and this occurs at the ankle. Without more late swing, negative work is performed by the knee flex- information, one cannot know whether the ankle ors (K4) as they work eccentrically to decelerate the leg plantarflexors are flexing or the dorsiflexors are dor- in preparation for initial contact. siflexing, but either moment or angle profiles reveal that the first is correct. The second largest burst of Inman estimated that the positive energy generated positive power, denoted H1-S, is an internal hip by the hip muscles during concentric muscle action for extensor moment with hip extension occurring in normal men walking at a cadence of 109 steps per early stance. The third burst, H3-S, occurs near A2-S. minute is approximately double the amount of energy It is caused by an internal hip flexor moment and absorbed by the hip muscles during eccentric muscle hip flexion at the end of stance and the beginning of action,3 but data suggest that the ratio is even larger.14 swing and may be called “pull-off.” At the ankle, the positive energy generated by concen- tric muscle action during a single gait cycle is almost The knee is not of major importance in energy triple that of the energy absorbed by eccentric muscle generation. However, there is a small phase, denoted action.3 The knee, in contrast to the hip and ankle, K2-S, in which the knee extensors extend the knee absorbs more energy through eccentric muscle action after the knee flexion phase of early stance. K2-S can during a gait cycle than it generates.3 At slow and nor- be important in pathologies such as cerebral palsy mal speeds of walking in healthy subjects, the hip flex- when other sources of energy are not available. ors and extensors contribute about 25% of the total concentric work. The ankle plantarflexors contribute Unless gait velocity is increasing, energy has to about 66%, and the knee extensors contribute about be systematically removed. The knee accomplishes 8%.32 Clearly, the ankle plantarflexors are of primary this at K1-S (knee flexion with an internal knee importance in walking (see Continuing Exploration: extensor moment) and K3-S (small internal knee On the Existence of “Rockers” and “Push-off”). extensor moment in late stance occurring while the knee is flexing quite quickly). The latter may repre- In the frontal plane (see Fig. 14-23), an initial sent inefficiency in gait.44 K4-S (knee flexor absorp- period of absorption by the hip abductors is followed by tion with knee extension) occurs before initial two small bursts of positive work in the remainder of contact. Note that, as with all absorption phases, the stance. These bursts provide fine control of the medio- dominating moment is opposite to the movement lateral position of the center of mass of the body. At that is occurring: in this case, an internal flexor the knee, there is a very small generation pattern dur- moment while knee extension is occurring. ing the first half of stance, followed by a small absorp- Let us now examine the periods during which simultaneous positive and negative work normally occur, which, if excessive, represents inefficiency. K1- S and A1-S are negative bursts of negative work con- Text continues on p. 542

Copyright © 2005 by F. A. Davis. 538 ■ Section 5: Integrated Function Muscle Activity GLUTEUS MAXIMUS HIP DEGREES flexion Sagittal WATTS / Kg GEN Sagittal 0 20 40 60 80 100 KNEE Joint Angle Joint Power MEDIAL HAMSTRING extension 30 ABS NORMALIZED ELECTROMYOGRAPHY (%) 2.0 H1-S H3-S 0 20 40 60 80 100 20 ILIOPSOAS 0 10 VASTUS LATERALIS -2.0 H2-S 0 0 20 40 60 80 100 0 20 40 60 80 100 RECTUS FEMORIS DEGREES flexion -10 WATTS / Kg GEN 1.2 KO-S K1-S 0 20 40 60 80 100 -20 LATERAL 0 HAMSTRING -30 extension 20 40 60 80 100 ABS K2-S K3-S K4-S 40 60 80 100 70 -2.5 60 0 20 50 40 30 20 10 0 20 40 60 80 100 Sagittal ANKLE DEGREES 10 GEN 2.0 A2-S 0 20 40 60 80 100 extension flexion SOLEUS 0 WATTS / Kg 0 -1.5 0 20 40 60 80 100 -10 ABS A1-S TIBIALIS ANTERIOR 0 20 40 60 80 100 -20 -30 20 40 60 80 100 % Gait Cycle 0 20 40 60 80 100 % Gait Cycle ▲ Figure 14-22 ■ Joint angles and joint powers in the sagittal plane, and EMG profiles of representatives of major contributors to joint powers of hip, knee, and ankle during adult gait. (Angle profiles redrawn from Winter DA, Eng JJ, Isshac MG: A review of kinetic parameters in human walking. In Craik RL, Otis CA [eds]: Gait Analysis: Theory and Application, pp. 263-265. St. Louis, Mosby–Year Book, 1994, with per- mission from Elsevier. Power profiles redrawn from Eng JJ, Winter DA: Kinetic analysis of the lower limbs during walking: What information can be gained from a three dimensional model? J Biomech 28:753, 1995, with permission from Elsevier. Muscle activity redrawn from Winter DA: The Biomechanics and Motor Control of Human Gait: Normal, Elderly and Pathological, 2nd ed. Waterloo, Ontario, Waterloo Biomechanics, 1991, with permission from David A. Winter. Iliopsoas muscle activity redrawn from Bechtol CO: Normal human gait. In American Academy of Orthopaedic Surgeons: Atlas of Orthotics, p 141. St. Louis, CV Mosby, 1974, with permission from Elsevier.)

Copyright © 2005 by F. A. Davis. Chapter 14: Gait ■ 539 Muscle Activity GLUTEUS MEDIUS Frontal Frontal NORMALIZED ELECTROMYOGRAPHY (%) Joint Angle Joint Power adduction 12.5 20 40 60 GEN 0.75 H3-F 0 20 40 60 80 100 10.5 0 ADDUCTOR MAGNUS HIP H2-F ANGLE (deg) 7.5 abduction 5.0 WATTS / Kg 2.5 ABS -1.50 H1-F 0.0 0 20 40 60 80 100 -2.5 80 100 0 20 40 60 80 100 -5.0 -7.5 (Ligamentous) TENSOR FASCIA LATAE 0 adduction 5.0 2.5 KNEE 0.0 GEN 0.35 ANGLE (deg) -2.5 K1-F -5.0 abduction -7.5 WATTS / Kg 0 -10.0 ABS -0.30 K2-F 0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100 PERONEUS LONGUS dnucrsion 15.0 NORMALIZED ELECTROMYOGRAPHY (%) ANGLE (deg) 10.0 GEN A1-F 0.15 ANKLE 5.0 WATTS / Kg 0 20 40 60 80 100 0 TIBIALIS ANTERIOR eversion 0.0 0 20 40 60 80 100 -5.0 ABS -0.25 0 0 20 40 60 80 100 20 40 60 80 100 % Gait Cycle % Gait Cycle ▲ Figure 14-23 ■ Joint angles and joint powers in the frontal plane, and EMG profiles of representatives of major contributors to joint powers of hip, knee, and ankle during adult gait. (Angle profiles redrawn from Winter DA, Eng JJ, Isshac MJ: A review of kinetic parameters in human walking. In Craik RL, Otis CA [eds]: Gait Analysis: Theory and Application, pp 263-265. St. Louis, Mosby–Year Book, 1994, with per- mission from Elsevier. Power profiles redrawn from Eng JJ, Winter DA: Kinetic analysis of the lower limbs during walking: What information can be gained from a three dimensional model? J Biomech 28:753, 1995, with permission. Muscle activity redrawn from Winter DA: The Biomechanics and Motor Control of Human Gait: Normal, Elderly and Pathological, 2nd ed. Waterloo, Ontario, Waterloo Biomechanics, 1991. with permission from David A. Winter.)

Copyright © 2005 by F. A. Davis.Int. Rot Transverse 540 ■ Section 5: Integrated Function Joint Power TransverseHIPDEGREES GEN 0.030 Joint Angle 0 WATTS / Kg 3Ext. Rot 1 ABS -1 0.350 H1-T -3 0 20 40 60 80 100 -5 -7Int. Rot WATTS / Kg GEN 0 20 40 60 80 100KNEEDEGREES 0.075 10.0 0 5.0Ext. Rot K1-T 0.0 ABS -0.300 0 -5.0 20 40 60 80 100 -10.0 0 20 40 60 80 100 15.0 Int. Rot 10.0 GEN 0.050 5.0 0 ANKLE DEGREES 0.0 WATTS / Kg Ext. Rot ABS -5.0 20 40 60 80 100 -0.050 20 40 60 80 100 0 % Gait Cycle 0 ▲ Figure 14-24 ■ Joint angles and joint powers in the transverse plane of hip, knee, and ankle during adult gait. (Angle profiles redrawn from Winter DA, Eng JJ, Isshac MG: A review of kinetic parameters in human walking. In Craik RL, Otis CA [eds]: Gait Analysis: Theory and Application, pp. 263-265. St. Louis, Mosby–Year Book, 1994, with permission from Elsevier. Power profiles redrawn from Eng JJ, Winter DA: Kinetic analysis of the lower limbs during walking: What information can be gained from a three dimensional model? J Biomech 28:753, 1995, with permission from Elsevier.)

Copyright © 2005 by F. A. Davis. Chapter 14: Gait ■ 541 Table 14-3 Summary of Gait Characteristics from Initial Contact to Midstance: Sagittal Plane Analysis Joint Motion Ground Reaction Internal Moment Power Major Muscle Hip Force Activity Knee Extends from Generation (hip Gluteus maximus ϩ20Њ–ϩ30Њ to 0Њ Anterior to posterior Extensor to neutral extensors) Hamstrings Hamstrings Flexes from 0Њ to Anterior to posterior Flexor, then exten- Generation (knee ϩ15Њ, then extends to anterior sor then flexor flexors) Quadriceps ϩ15Њ to ϩ5Њ Hamstrings Absorption (knee Gastrocnemius Ankle Plantarflexes from 0Њ Posterior to anterior Dorsiflexor, then extensors) to Ϫ5Њ, then dorsi- plantarflexor Tibialis anterior flexes to ϩ5Њ Generation (knee extensors) Soleus Gastrocnemius Absorption (knee flexors) Absorption (dorsi- flexors) Generation (plan- tarflexors) Frontal Plane Analysis Joint Motion Ground Reaction Moment Power Major Muscle Hip Force Activity Adduction from neu- Absorption (hip Gluteus medius tral to ϩ5Њ, then Medial Abductor abductors) abduction to 3Њ Tensor fasciae Generation (hip latae Knee Small variation Medial Abductor abductors) around neutral Peroneus longus Small generation Peroneus brevis Ankle Everts from 5Њ inver- Medial Very small everter (knee abduc- Tibialis anterior sion to 5Њ eversion then neutral or tors) small inverter Small generation (everters) Very small absorp- tion (inverters) Small generation (everters) Transverse Plane Analysis Joint Motion Moment Power Major Muscle Activity Hip Externally rotates a External rotator Absorption (internal Tensor fasciae latae few degrees rotators) Gluteus medius Knee From several degrees Very small external Small absorption Gluteus minimus Ankle of external rota- rotator (external rotators) (Ligamentous) tion, rotates inter- nally to neutral External rotator Extremely small — Externally rotates from ϩ5Њ internal rotation to Ϫ5Њ external rotation, then to neutral Redrawn from Eng JJ, Winter DA: Kinetic analysis of the lower limbs during walking: What information can be gained from a three dimen- sional model? J Biomech 28:753, 1995; and from Winter DA, Eng JJ, Isshac MG: A review of kinetic parameters in human walking. In Craik RL, Otis CA (eds): Gait Analysis: Theory and Application. St. Louis, Mosby–Year Book, 1994. Values are for young males.

Copyright © 2005 by F. A. Davis. 542 ■ Section 5: Integrated Function Table 14-4 Summary of Gait Characteristics from Midstance to Toe-off Sagittal Plane Analysis Joint Motion Ground Power Major Muscle Hip Reaction Force Moment Activity Knee Extends from 0Њ to Ϫ20Њ Absorption (flexors) extension, then Posterior Flexor Iliopsoas Ankle begins to flex Generation (flexors) Rectus femoris Posterior Flexor, then Iliopsoas From ϩ5Њ extends a few extensor Absorption (extensors) Rectus femoris degrees, then flexes to Small generation (knee Vastus about ϩ45Њ Anterior Plantarflexor Gastrocnemius flexors) From ϩ5Њ dorsiflexion, Large absorption Rectus femoris dorsiflexes a few more degrees, then rapidly (extensors) Soleus plantarflexes to Ϫ25Њ Very small absorption Gastrocnemius Soleus (plantarflexors) Gastrocnemius Large generation (plan- tarflexors) Frontal Plane Analysis Joint Motion Ground Power Major Muscle Hip Reaction Force Moment Generation (abductors) Activity Knee From ϩ3Њ smoothly Absorption (abductors) abducts to Ϫ5Њ Medial Abductor Gluteus medius Ankle Very small generation Neutral, then abducts to Medial Abductor Absorption (evertors) Tensor fasciae a few degrees Ϫ3Њ latae, liga- Medial Inverter, then ments Ϫ5Њ everter Peroneus longus Peroneus brevis Transverse Plane Analysis Joint Motion Moment Power Hip From Ϫ3Њ, externally Internal Very small Knee rotates a few more rotator absorption degrees (external Ankle Internal rotators) Remains near neutral rotator Very small From neutral, rotates External absorption about 7Њ, then back to rotator (ligamen- neutral tous) Variable Redrawn from Eng JJ, Winter DA: Kinetic analysis of the lower limbs during walking: What information can be gained from a three dimen- sional model J Biomech 28:753, 1995; and from Winter DA, Eng JJ, Isshac MG: A review of kinetic parameters in human walking. In Craik RL, Otis CA (eds): Gait Analysis: Theory and Application. St. Louis, Mosby–Year Book, 1994. Values are for young males. current with H1-S, which is positive. K3-S is negative degrees during swing phase. A power analysis of Ms. work occurring concurrently with both H3-S and Brown’s affected limb, if available, would have shown a A2-S. Values that are above normal represent exces- severely reduced A2-S and H3-S and virtual absence of sive inefficiency and usually result in slower walking an H1-S energy burst. The first two would be apparent speeds. to the therapist as no firm push-off29 and no rapid hip flexion. This meant that Ms. Brown would be unable to C a s e A p p l i c a t i o n 1 4 - 6 : Continuing Gait Problems push off strongly (A2-S) or pull off strongly (H3-S), because both actions require knee flexion. Every attempt It was noted that Ms. Brown tended to fully extend her was made during gait training to gain knee control in knee in midstance and then flexed her knee only a few midstance, not permitting it to fully extend. Strong push- off and strong “pull-off” then could be encouraged.

Copyright © 2005 by F. A. Davis. Because the hip extensors on the affected side were Chapter 14: Gait ■ 543 among the least affected muscles, Ms. Brown was encouraged to exploit H1-S, the “push from behind” in is often used in conjunction with force plates, goniom- early stance. Stronger activity of A2-S, H1-S, and H3-S etry, and/or motion analysis systems to link the muscle on the unaffected side, especially later in stages of activity with other events during the gait cycle. The rehabilitation, would be encouraged to provide interlimb EMG record provides information about when only compensation for the reduced activity on the affected particular muscles are acting and the relative level, or side. Gait speed would increase to the degree that these profile, of their activity. It does not tell why the muscles efforts are effective. are acting or how much force the muscles are generat- ing. The reader is encouraged to follow the developing Continuing Exploration: On the Existence literature on muscle function that is derived from elab- of “Rockers” and “Push-Off” orate mathematical simulations that involve modeling precise muscle geometry and anthropometrics.46–48 There has been some controversy concerning these Although this work has just begun, it is already chal- two terms. Orthopedic literature frequently refers to lenging conventional assumptions about the function three “rockers” as characterizing the kinematics of of muscles. the foot and ankle during stance phase. The “first rocker” or “initial rocker” occurs from initial contact EMG studies of gait are used to augment the under- until foot flat and has a fulcrum about the heel (heel standing provided by a link segment analysis, to validate pivot). The “second rocker” or “midstance rocker” is theoretical models that attempt to explain why muscles described as occurring between foot flat and heel-off are needed for certain functions, and in theoretical and has a fulcrum about the ankle joint. The “third models developed to explain the muscle activity found rocker” or “terminal rocker” occurs between heel-off by EMG.53 The EMG reported in the section that fol- and toe-off (push-off), with the leg rotating about lows is derived from the work of Winter.14 the forefoot. Although not incorrect, it is preferable that standard terminology be used. The muscle work of gait can be simplified by antic- ipating the muscle groups that must be functioning for Before kinetic link segment analysis was com- specific purposes and then adding detailed variations mon, there were objections to the term “push-off.” It when the general pattern is clear. Muscle work is logi- was thought that the second peak in the vertical cal, and the reader already knows that two major fea- floor reaction force resulted from changes in body tures are going to determine its patterns: the need to alignment, rather than an increasing force resulting provide a support moment through stance and the need from plantarflexor contraction. However, the work to generate energy to move. of Winter45 and others44,46,47 shows that push-off not only exists but is normally responsible for a major Let us follow the logic of what muscle work is likely portion of the work of walking. It is clear that a per- to be needed for the support moment (see Fig. 14-17) son with no ankle plantarflexion (hence no power and compare results with Figures 14-25, 14-26, and 14- generation at the ankle) can walk, however. Some 27. The support moment is made up of some combina- compensation can be provided by H1-S and H3-S tion of hip extensors, knee extensors, and ankle from both limbs, although people with rigid ankle plantarflexors. We already have discussed the fact that foot orthoses or inflexible prostheses usually walk the hip extensors produce an internal extensor more slowly than normal. moment early in stance; next, knee extensors produce an internal knee extensor moment, and then internal Zajac and colleagues and other researchers flexor moments are produced at both the hip and knee using similar models have shown that the energy before the knee and hip bend in late stance in prepara- produced by the soleus muscle in late stance is deliv- tion for swing phase. While these two muscle groups are ered to the trunk to accelerate it forward, but the flexing the segmented system, the ankle plantarflexors increase in trunk energy is more than that produced take the lead and provide support. We should not be by the soleus muscle.47,48 It appears that the soleus, surprised, then, to find activity in the hip extensors rectus femoris, and gastrocnemius work synergisti- (hamstrings) early in stance and knee extensors cally to ensure forward acceleration of the trunk. (quadriceps) almost immediately after, followed by a These studies show that muscles not only generate smoothly increasing contraction of the ankle plan- and absorb energy but, in many cases, serve to redis- tarflexors (soleus, medial, and lateral gastrocnemius tribute energy. muscles and other minor contributors) that continues until mid-push-off and then declines and ceases at Muscle Activity about 60% of the cycle. Muscle activity can be identified by EMG, a technique Now let us look for the muscle work that is respon- in which the electrical activity generated by an active sible for the main bursts of positive work, relating mus- muscle is recorded. There is a great deal of information cle work shown in Figures 14-25 to 14-27 to power about EMG, the varieties of techniques that can be profiles shown in Figures 14-22 to 14-24. In the sagittal used, and the patterns obtained during gait.24,49–53 EMG plane, we note that the hip extensors (gluteus max- imus, medial hamstring, and lateral hamstring muscles) are active in early stance (H1-S); indeed, they were serv- ing the function of providing support during that period. The small energy-generating K2-S that peaks in early stance is reflected in activation of the quadriceps (vastus medialis, vastus lateralis, and rectus femoris

Copyright © 2005 by F. A. Davis. 250 ADDUCTOR MAGNUS N=11 544 ■ Section 5: Integrated Function 200 MEAN (ᒒV)=42.7 150 400 GLUTEUS MAXIMUS N=16 100 300 MEAN (ᒒV)=16.4 200 50 100 0 0 00 0500 MEDIAL HAMSTRING N=23 250 ADDUCTOR LONGUS N=16 20 20 20 40 40 40 60 60 60 80 80 80 100 100 100 00 0 20 20 20 40 40 40 60 60 60 80 80 80 100 100 100 MEAN (ᒒV)=68.5 400 200 Text/image rights not available.300 150 MEAN (ᒒV)=33.9 200 100 100 50 00 400 LATERAL HAMSTRING N=27 400 GLUTEUS MEDIUS N=26 300 MEAN (ᒒV)=54.5 300 200 MEAN (ᒒV)=29.7 200 100 100 00 300 SARTORIUS N=15 rights 300 TENSOR FASCIA LATAE N=8 ᭣ Figure 14-25 ■ Electro- 250 250 MEAN (ᒒV)=25.5 myographic activity profiles of major not available.200 muscle groups of the hip during one Te2150x00 t/image MEAN (ᒒV)=34.5 stride of gait with probable roles. 150 Signals were derived from bipolar 100 100 surface electrodes as data normal- 50 ized to means for each subject. Note 50 0 absence of the profile for the hip flexor, the iliopsoas muscle, which is 0 inaccessible to surface electrodes. (Redrawn from Winter DA: The 0 Biomechanics and Motor Control of 20 Human Gait: Normal, Elderly and 40 Pathological, 2nd ed. Waterloo, 60 Ontario, Waterloo Biomechanics, 80 1991, with permission from David A. 100 Winter.) 0 20 40 60 80 100 muscles). Recall that the largest contribution to the contraction as the hip extends (H2-S); then the muscle work of walking comes from the ankle plantarflexors force overcomes the opposing force and begins to act (largely soleus, medial, and lateral gastrocnemius mus- concentrically, causing an energy-generating “pull-off “ cles). These muscles work eccentrically (lengthening) phase (H3-S). The iliopsoas muscle is the major hip from early stance until about 40% of the gait cycle, flexor, but it is inaccessible to surface electrodes. when they overcome the dorsiflexing moment of the However, the rectus femoris muscle is the only quadri- foot-floor force (GRF; see later discussion) and pro- ceps muscles that crosses the hip and whose activity in duce a burst of concentric activity (A2-S) ending at toe- late stance is known to correlate with that of iliopsoas. off, at about 60% of the gait cycle. A similar sequence We can see rectus femoris activity peaking around 70% of first eccentric and then concentric activity occurs in of the cycle, reflecting the hip-flexor function. the hip flexors (iliopsoas and rectus femoris muscles). First they lengthen, producing an energy-absorbing Now let us look at the major energy-absorbing phases and the muscle groups that are responsible.

Copyright © 2005 by F. A. Davis. Chapter 14: Gait ■ 545 500 VASTUS LATERALIS N=15 PERONEUS LONGUS N=19 400 400 300 300 MEAN(ᒒV)=56 200 MEAN (ᒒV)=61.5 100 200 100 0 0 00 0400 VASTUS MEDIALIS N=24 400 PERONEUS BREVIS N=10 20 20 20 300 40 40 40300 60 60 60MEAN (ᒒV)=50.4 MEAN (ᒒV)=117.3 80 80 80 200 100 100 100200 100 00 0100 0 20 20 20 40 40 400 60 60 60 80 80 80 100 100 100 400 RECTUS FEMORIS N=28 400 MEDIAL GASTROCNEMIUS N=25 300 MEAN (ᒒV)=21.8 MEAN (ᒒV)=110.7 300 Te210000xt/image rights200 not available. 100 00 350 TIBIALIS ANTERIOR N=26 LATERAL GASTROCNEMIUS 300 400 N=10 250 MEAN (ᒒV)=139 300 MEAN (ᒒV)=79.2 200 200 150 100 100 50 0 0 00 20 20 40 40 60 60 80 80 100 100 00 20 20 40 40 60 60 80 80 100 100 300 EXTENSOR DIGITORUM LONGUS 400 SOLEUS N=18 250 N=12 300 MEAN (ᒒV)=113 200 MEAN (ᒒV)=98 150 200 100 100 50 0 0 ▲ Figure 14-26 ■ Electromyographic activity profiles of major muscle groups of the knee and ankle during one stride of gait with prob- able roles. Signals were derived from bipolar surface electrodes as data normalized to means for each subject. (Redrawn from Winter DA: The Biomechanics and Motor Control of Human Gait: Normal, Elderly and Pathological, 2nd ed. Waterloo, Ontario, Waterloo Biomechanics, 1991, with permission from David A. Winter.)

Copyright © 2005 by F. A. Davis. 546 ■ Section 5: Integrated Function 180 SPLENIUS CAPITUS N=12 250 TRAPEZIUS (UPPER) N=11 200 MEAN (ᒒV)=24.2 160 150 100 140 50 120 0 100 80 60 40 MEAN (ᒒV)=13.9 20 0 ERECTOR SPINAE-T90 00 ERECTOR SPINAE-L3-L4 500 20 20 20 300 40 40 40 N=1260 60 60 N=11 80 80 80 400 MEAN (ᒒV)=39 100 100 100 MEAN (ᒒV)=27.7 200 000 300 20 20 20 40 40 40 60 60 60 80 80 80 100 100 100 Te200xt/image righ1t0s0 not available. 100 00 250 EXTERNAL OBLIQUE- LATERAL 180 RECTUS ABDOMINUS N=11 N=10 160 140 200 150 120 100 100 80 60 50 40 MEAN (ᒒV)=7.3 MEAN (ᒒV)=24.3 20 00 ▲ Figure 14-27 ■ Electromyographic activity profiles of major muscle groups of the trunk during one stride of gait with probable roles. Signals were derived from bipolar surface electrodes as data normalized to means for each subject. (Redrawn from Winter DA: The Biomechanics and Motor Control of Human Gait: Normal, Elderly and Pathological, 2nd ed. Waterloo, Ontario, Waterloo Biomechanics, 1991, with permission from David A. Winter.) K1-S, occurring before 20% of the cycle, is the eccentric the end of swing, is reflected in EMG records as activa- phase of the knee extensors (vastus lateralis, medialis, tion of the medial and lateral hamstrings. Note that the intermedius and rectus femoris), which precedes its gastrocnemius muscles, which cross the knee as well as concentric K2-S energy-generating phase. We have dis- the ankle, also begin activity in late swing phase. At the cussed H2-S, the eccentric action of the hip flexors ankle, A1-S absorption through much of early stance (iliopsoas and rectus femoris), during midstance and and midstance is attributable to ankle plantarflexor late stance. Note that the knee extensor and the hip activity, which we have already discussed. extensor muscles begin their contraction at the end of swing phase, although at this time the dominant Now let us see whether we have missed any major moments are being provided by the knee flexors; in EMG features by deducing muscle activity from support other words, there is a period of co-contraction that is moment and power profiles. First, in the sagittal plane, invisible to a link segment analysis but evident from the ankle dorsiflexors (tibialis anterior, extensor digi- EMG. K3-S is a small energy-absorbing internal knee torum longus, and extensor hallucis longus muscles) extensor moment occurring while the knee is flexing are active eccentrically across the ankle before foot flat rapidly (~50% to 70% of cycle), and this is reflected in to lower the foot to the floor, are active again to hold low levels of contraction of the vastus muscles, particu- the foot at a neutral angle during swing phase, and larly the rectus femoris, which, because it crosses both show varying but small levels of activity at other times of hip and knee, is active at that time as a hip flexor the cycle, probably positioning the foot. In the frontal (H3-S). K4-S, energy absorption of the knee flexors at plane, the activity of hip abductor gluteus medius, along with gluteus minimus and tensor fasciae latae

Copyright © 2005 by F. A. Davis. muscles (not shown), controls the lateral drop of the Chapter 14: Gait ■ 547 pelvis on the side of the swinging leg, closely mimicking the pattern of the vasti.49 Activity of these muscles this period of energy absorption is so small in magni- diminishes during midstance and ceases when the tude that it does not appear on power profiles. It is, opposite limb has contacted the ground.12 however, functionally important. Adductor longus and brevis muscles, acting in both Example 14-2 frontal and sagittal planes, show two fairly equal peaks of activity at ~10% and 65% to 80% of the gait cycle. The GRFV tending to flex the hip (external flexion The first is concurrent with the hip abductors and may moment) and extend the knee (external extension be providing stabilization; the second is early in swing, moment) at initial contact (see Fig. 14-31) is consistent providing hip flexion to assist iliopsoas and rectus with the opposition provided by an internal hip exten- femoris muscles. Further information can be found in sor moment (hamstrings and gluteus maximus) and the literature.49,51,52 Trunk muscle activity is discussed in internal knee flexor moment (hamstrings) shown in a later section. Figure 14-28. Ground Reaction Force: C a s e A p p l i c a t i o n 1 4 - 7 : Internal Hip and Sagittal Plane Analysis Knee Flexors Before full dynamic biomechanical gait analyses were At heel-off (~40% of gait cycle), the GRFV tending to common, attempts were made to link in a visual way the extend the hip and knee (see Fig. 14-32) is consistent static information from the GRF to the joint positions with the opposition provided by the internal hip flexor during gait. There are errors in this kind of analysis moment (iliopsoas and rectus femoris muscles) and because dynamic factors are not included, but during the internal knee flexor moment (gastrocnemius mus- stance phase, these are minimal. Also, they cause less cles) (see Fig. 14-28). Consider the effects of a larger error nearer the force platform. Small errors are pro- than normal tendency to extend the knee, which duced at the ankle that become larger at the hip, espe- occurred, for example, when Ms. Brown thrust her knee cially at times of push-off and initial contact.54 If they back into full extension in an effort to gain knee stability are used to attempt to reconcile with the internal (Fig. 14-33). Because the knee flexors that are active at moment profiles of Figures 14-28 to 14-30, however, that time (gastrocnemius muscles) did not overcome they can add important understanding and helpful this excessive moment, Ms. Brown had difficulty flexing visualization of normal gait for stance phase of gait the knee, which prevented flexion of both the hip and (inasmuch as, of course, there is no GRF during swing the ankle and reduced the opportunity to generate work phase). The general sequence of the most common from the ankle at A2-S and the hip at H3-S. Avoiding pattern of GRFV for stance phase is shown in Figure this “knee locking” in stance by rigorous encouragement 14-31 (initial contact to midstance) and Figure 14-32 of knee flexion at the end of stance and by temporary (midstance to toe-off). These should be related to inter- use of an ankle-foot orthosis was important in Ms. nal moment profiles appearing in Figure 14-28 to 14-30. Brown’s gait reeducation. The analyses included show the location of the GRF in relation to the joints of the lower extremities. The loca- CONCEPT CORNERSTONE 14-3: What Gait Information tion of the GRFV, joint positions, and muscle activity Is Important? that were used to create the illustrations were derived from published studies on normal human walking.3,8,55 Given the availability of information about walking, it is often not Three examples of practical applications will illustrate clear what information is helpful for any given situation. First, it is this process, and the reader is encouraged to attempt important to determine why you want the information. Usually the others independently. reasons include one or more of the following: (1) to gain an under- standing of normal or pathological gait; (2) to assist movement Example 14-1 diagnosis and identify specific causes of pathological gait; (3) to inform treatment selection; and (4) to evaluate the effectiveness of In the period of gait from initial contact to the end of treatment. Second, you may ask what gait measures are impor- midstance, the ankle moves from the neutral position tant for the situation. For example, if you want to know whether at initial contact to 15Њ of plantarflexion by the end of energy costs are decreased with provision of an ankle orthosis, a loading response and to 10Њ of dorsiflexion by the end measure of self-selected speed of walking may be sufficient. If you of midstance. The GRFV changes from a location pos- want to know which muscle groups could be exploited to gain terior to the ankle joint at initial contact to an anterior increased walking speed in treating a person with a neurological position in midstance (see Fig. 14-31). Therefore, at ini- condition, you would want to see a power analysis. If you wished tial contact and during loading response (heel strike to to know whether a new ankle-foot orthosis really did return energy foot flat), there is an external plantarflexion moment, during push-off, you would also want a power analysis. If you and the ankle is moving in a direction of plantarflex- ion. An eccentric contraction of the dorsiflexors con- Text continues on p. 551 trols the motion, and negative work is done. Note that

Copyright © 2005 by F. A. Davis. 548 ■ Section 5: Integrated Function Muscle Activity GLUTEUS MAXIMUS 20 40 60 80 100 Sagittal Sagittal MEDIAL HAMSTRING Joint Angle Joint Moment 30 20 40 60 80 100 flexion extensor 1.25 ILIOPSOAS 20 0.75 DEGREES Nm/kg 0.25 20 40 60 80 100 10extension -0.25 HIP 0 flexor -0.75 -10 -20 -30 -1.25 VASTUS LATERALIS 20 40 60 80 100 0 20 40 60 80 100 flexion 70 Nm/kg 0.75 Normalized Electromyography (%) 20 40 60 80 100 60 extensor 0.50 KNEE DEGREES 50 0.25 MEDIAL 40 0.00 GASTROCNEMIUS extension 30 flexor -0.25 20 -0.50 20 40 60 80 100 10 0 20 40 60 80 100 LATERAL HAMSTRING 0 20 40 60 80 100 Sagittal dorsi 10 plantar 1.75 20 40 60 80 100 flexion 0 extensor 1.25 SOLEUS -10 0.75 ANKLE plantar DEGREES -20 Nm/kg 0.50 20 40 60 80 100 extension dorsi flexor -30 0.25 100 TIBIALIS ANTERIOR 20 40 60 80 100 0 20 40 60 80 % Gait Cycle % Gait Cycle 20 40 60 80 100 % Gait Cycle ▲ Figure 14-28 ■ Joint angles and net joint moments in the sagittal plane, and EMG profiles of representatives of major contributors to joint moments of hip, knee, and ankle during adult gait. (Angle and moment profiles redrawn from Winter DA, Eng JJ, Isshac MG: A review of kinetic parameters in human walking. In Craik RL, Otis CA [eds]: Gait Analysis: Theory and Application, pp 263-265. St. Louis, Mosby–Year Book, 1994, with permission from Elsevier. Muscle activity redrawn from Winter DA: The Biomechanics and Motor Control of Human Gait: Normal, Elderly and Pathological, 2nd ed. Waterloo, Ontario, Waterloo Biomechanics, 1991, with permission from David A. Winter. Ilopsoas muscle activity redrawn from Bechtol CO: Normal human gait. In American Academy of Orthopaedic Surgeons: Atlas of Orthotics, p 141. St. Louis, CV Mosby, 1974, with permission from Elsevier.)

Copyright © 2005 by F. A. Davis. Chapter 14: Gait ■ 549 Muscle Activity GLUTEUS MEDIUS adduction 12.5 Frontal abductor 1.50 Frontal 10.5 Joint Angle 1.25 Joint Moment ANGLE (deg) 1.00 Normalized EMG (%) 20 40 60 80 100 7.5 20 40 60 0.75 20 40 60 GLUTEUS MEDIUS HIP 5.0 (N.m/kg) 0.50 adductor 0.25 abduction 2.5 0.00 0.0 -0.25 -2.5 80 100 80 100 -5.0 0 -7.5 0 20 40 60 80 100 5.0 0.95 ( largely ligamentous) adduction abductor 2.5 0.75 TENSOR FASCIA LATAE KNEE 0.0ANGLE (deg) (N.m/kg)rights0.55 not Normalized EMG (%)available. 0.35 Text/image-2.5 abduction -5.0 0.15 -7.5 -0.05 20 40 60 80 100 adductor -10.0 -0.25 0 20 40 60 80 100 0 20 40 60 80 100 Normalized Electromyography (%) PERONEUS LONGUS 0.25 inversion 15.0 evertor ANKLE ANGLE (deg) 10.0 0.15 20 40 60 80 100 5.0 (N.m/kg) 0.05 eversion 0.0 invertor -5.0 20 40 60 80 100 -0.05 20 40 60 80 100 20 40 60 80 100 0 % Gait Cycle 0 % Gait Cycle % Gait Cycle ▲ Figure 14-29 ■ Joint angles and net joint moments in the frontal plane, and EMG profiles of representatives of major contributors to joint moments of hip, knee, and ankle during adult gait. (Angle and moment profiles redrawn from Winter DA, Eng JJ, Isshac MG: A review of kinetic parameters in human walking. In Craik RL, Otis CA [eds]: Gait Analysis: Theory and Application, pp 263-265. St. Louis, Mosby–Year Book, 1994, with permission from Elsevier. Muscle activity redrawn from Winter DA: The Biomechanics and Motor Control of Human Gait: Normal, Elderly and Pathological, 2nd ed. Waterloo, Ontario, Waterloo Biomechanics, 1991, with permission from David A. Winter.)

Copyright © 2005 by F. A. Davis.Int.Rot Ext. Rot Transverse 550 ■ Section 5: Integrated Function Moment DEGREES N.m/kg 0.25 TransverseExt. Rot Joint Angle Int. Rot 0.15 3 Int.Rot Ext. Rot 0.05 1 DEGREES N.m/kg -0.05 -1 HIPExt. Rot Int. Rot -0.15 -0.25 -3 0 20 40 60 80 100 -5 0.15 -7 0.10 0 20 40 60 80 100 0.05 0.00 10.0 -0.05 -0.15 5.0 0 20 40 60 80 100 HIP 0.0 -5.0 -10.0 0 20 40 60 80 100 15.0 0.125 Int.Rot 0.100Ext. Rot 10.0 0.075 ANKLE DEGREES 5.0 N.m/kg 0.050 Ext. Rot 0.0 0.025 Int. Rot 0.000 -5.0 0 20 40 60 80 100 0 20 40 60 80 100 % Gait Cycle % Gait Cycle ▲ Figure 14-30 ■ Joint angles and net joint moments in the transverse plane, and EMG profiles of representatives of major contributors to joint moments of hip, knee, and ankle during adult gait. (Angle and moment profiles redrawn from Winter DA, Eng JJ, Isshac MG: A review of kinetic parameters in human walking. In Craik RL, Otis CA [eds]: Gait Analysis: Theory and Application, pp 263-265. St. Louis, Mosby–Year Book, 1994, with permission from Elsevier. Muscle activity redrawn from Winter DA: The Biomechanics and Motor Control of Human Gait: Normal, Elderly and Pathological, 2nd ed. Waterloo, Ontario, Waterloo Biomechanics, 1991, with permission from David A. Winter.)

Copyright © 2005 by F. A. Davis. Chapter 14: Gait ■ 551 GRFV GRFV GRFV Flexor moment Extensor 20˚ Extensor 15˚ moment flexion moment flexion 0˚ flexion 0˚ Extensor Flexor 5˚ moment moment flexion 0˚ Dorsiflexor Flexor moment 15˚ moment flexion CoP Initial contact 5˚ Dorsiflexor Plantar 5˚ Plantar moment flexor Dorsal flexion moment flexion CoP CoP Foot flat Midstance ▲ Figure 14-31 ■ Diagram of joint positions with center of pressure (CoP), ground reaction force vector (GRFV), and internal net moments of force for gait cycle events of initial contact, foot flat, and midstance. GRFV Flexor GRFV GRFV moment Flexor Flexor moment moment 0˚ 20˚ flexion extension Flexor Flexor 30˚ Extensor moment moment flexion moment 5˚ 0˚ flexion Plantar 5˚ Plantar 0˚ Flexor Plantar 25˚ flexor Dorsal flexor CoP moment flexor Plantar moment flexion moment moment flexion (toes) CoP (Toes) 60˚ Flexor hyperextension moment CoP (toes) Midstance Heel off Toe off ▲ Figure 14-32 ■ Diagram of joint positions with center of pressure (CoP), ground reaction force vector (GRFV), and internal net moments of force for gait cycle events of midstance, heel-off, and toe-off. wanted to determine whether surgery to realign the tibia and fibula heel strike and an extension peak of low amplitude was successful in decreasing a varus or valgus moment on the occurred during single limb support. Winter ex- knee, you would want a moment analysis in the frontal plane. plained14 that at initial contact, the forward accelera- There is a tendency for power analyses to be more useful in neu- tion of the HAT is quite large and acts at a distance rological conditions and moment analyses in musculoskeletal con- from the hip joint, thus producing an unbalancing ditions, particularly those involving pain. moment that acts strongly to cause flexion of the trunk during WA. However, an almost equal and oppo- Kinematics and Kinetics of the site internal moment is provided by the hip exten- Trunk and Upper Extremities sors (which we have seen before in their role in support and in energy generation at H1-S). In the frontal plane, Trunk a similar situation exists. The center of mass of the HAT, always being medial to the hip joint, exerts a The trunk remains essentially in the erect position considerable moment that is balanced primarily by during normal free-speed walking on level ground, an internal hip abductor moment from the support- varying only 11/2Њ.56 Krebs and coworkers57 found that ing limb and is assisted by the medial acceleration of a flexion peak of low amplitude occurred near each the hip. The biomechanical models used previously in the chapter do not distinguish between the pelvis and the

Copyright © 2005 by F. A. Davis. 552 ■ Section 5: Integrated Function Trunk leans right 2-3 cm Right arm swings Trunk rotates back about 24˚ a few degrees Pelvis rotates Left arm swings 4˚- 8˚ forward about 6˚ CoP Right Left ▲ Figure 14-33 ■ GRFV passing excessively anterior to knee joint center, making it difficult for the person to flex the knee. trunk. In the sagittal plane, the pelvis moves sinu- ▲ Figure 14-34 ■ Pelvis, trunk, and arm motion. Note that the soidally up and down 4 or 5 cm with each step, the low trunk and arms rotate in a direction opposite to that of the pelvis. point coinciding with initial contact of each foot and the high point coinciding with midstance. In the were considered along with anterior and posterior frontal plane, the pelvis translates from side to side pelvic tilting, lateral pelvic tilting, and rotation. about the same amount toward the standing limb and Mediolateral translations of the trunk occur as side-to- rotates downward about 5Њ toward the swinging limb on side motions (leans) in relation to the pelvis. For exam- each side. In the transverse plane, looking at it from ple, the trunk is leaning or moving to the right from above, it rotates 4Њ to 8Њ counterclockwise during swing right heel strike to left toe-off, at which point the trunk phase of the right limb, goes through neutral position begins a lean to the left until right toe-off. The average about midstance, then continues rotating the same total ROM that occurs during the mediolateral trunk amount in preparation for left foot initial contact. leans is about 5.4 cm.58 Hirasaki and coworkers59 used a When the pelvis rotates counterclockwise, preparing treadmill and a video-based motion analysis system to for initial contact of the right foot, the trunk rotates study trunk and head movements at different walking clockwise with regard to the pelvis to keep it directed speeds. These authors found that the relationship forwards. The amount of transverse rotation of the between walking speed and head and trunk movements trunk during gait is slight and occurs primarily in a was the most linear in the range of walking speeds from direction opposite to the direction of pelvic rotation 1.2 to 1.8 m/sec. At velocities above and below this (Fig. 14-34). As the pelvis rotates forward with the range, head and trunk movements were less well coor- swinging lower extremity, the thorax on the opposite dinated. side rotates forward as well. Actually, the thorax under- goes a biphasic rotation pattern with a reversal directly EMG profiles and probable functional roles are after liftoff of the stance leg. The thorax is rotated back- shown for some trunk muscles in Figure 14-27. Recent ward during double support and then slowly rotates for- EMG studies on the trunk muscles during gait have ward during single support. This trunk motion helps shown that there are subgroups of subjects show- prevent excess body motion and helps counterbalance ing similar patterns of muscle activity. White and rotation of the pelvis. Krebs and coworkers found that McNair,60 using a cluster analysis, demonstrated that at a free speed of gait, transverse rotation reached a there were two patterns of activity for the inter- maximum of 9Њ at 10% of the cycle after each heel nal oblique, external oblique, and rectus abdominis strike.57 In a study of treadmill walking, Stokes and muscles. In the lumbar erector spinae, there were three associates58 found that the movements and interactions patterns of activity observed. In the rectus abdominis of the trunk and pelvis were extremely complex when translatory and rotatory movements of the trunk

Copyright © 2005 by F. A. Davis. and external oblique muscles, most subjects had very Chapter 14: Gait ■ 553 low levels of activity throughout the gait cycle, but the internal oblique and erector spinae muscles had Stair and Running Gaits more distinct bursts, usually occurring close to initial contact. Other authors have shown two periods of activ- Stair Gait ity61 for the erector spinae muscle: one at initial contact and the second at toe-off. The erector spinae muscle is Ascending and descending stairs is a basic body move- thought to be active to oppose the unbalancing ment required for performing normal activities of moment that acts strongly to cause flexion of the trunk daily living such as shopping, using public transporta- during WA. tion, or simply getting around in a multistory home or building. Although many similarities exist between Upper Extremities level-ground locomotion and stair locomotion, the dif- ference between the two modes of locomotion Detailed kinetics of the upper extremity during normal may be significant for a patient population. The fact gait have not been reported, although extensive map- that a patient has adequate muscle strength and joint ping of EMG was classically performed several decades ROM for level-ground walking does not ensure that ago.61,62 Although the lower extremities are moving the patient will be able to walk up and down stairs. alternately forward and backward, the arms are swing- Stair walking represents additional stress over level- ing rhythmically. However, the arm swinging is opposite ground walking and may reveal differences that are not to that of the legs and pelvis but similar to that of the apparent in level-ground walking.65 trunk (see Fig. 14-34). The right arm swings forward with the forward swing of the left lower extremity while Krebs and coworkers57 found that trunk ROM dur- the left arm swings backward. This swinging of the arms ing level-ground gait was similar to trunk ROM during provides a counterbalancing action to the forward stair descent but differed from trunk ROM during stair swinging of the leg and helps to decelerate rotation of ascent in all planes. The maximum ROM of trunk flex- the body, which is imparted to it by the rotating pelvis. ion in relation to the room during stair ascent was at The total ROM at the shoulder is not very large. At nor- least double the amount of trunk flexion found in mal free velocities, the ROM is only approximately 30Њ either stair descent or in level-ground walking.57 (24Њ of extension and 6Њ of flexion). Locomotion on stairs is similar to level-ground The normal shoulder motion is the result of the walking in that stair gait involves both swing and stance combined effects of gravity and muscle activity. During phases in which forward progression of the body is the forward portion of arm swinging, the following brought about by alternating movements of the lower medial rotators are active: subscapularis, teres major, extremities. Also, in both stair and level-ground gait, and latissimus dorsi muscles. In backward swing, the the lower extremities must balance and carry along middle and posterior deltoid muscles are active HAT. McFayden and Winter (using step dimensions of throughout, and the latissimus dorsi and teres major 22 cm for the stair riser and 28 cm for the tread) per- muscles are active only during the first portion of back- formed a sagittal plane analysis of stair gait.66 These ward swing.61 The supraspinatus, trapezius,61 and pos- investigators collected kinetic and kinematic data for terior and middle deltoid muscles61 are active in both one subject during eight trials. The stair gait cycle for backward and forward swing. It is interesting to note stair ascent presented in Figure 14-35 is based on data that little or no activity was reported in the shoulder from McFayden and Winter’s study.66 The net internal flexors in these studies.61,62 It appears that during for- moments of the hip, knee, and ankle during stair ward swing, the medial rotators are acting eccentrically to control external rotation of the arm at the shoulder ▲ Figure 14-35 ■ Stair gait cycle. as the posterior deltoid acts eccentrically to restrain the forward swing. The latissimus dorsi and teres major muscles, as well as the posterior deltoid, may then act concentrically to produce the backward swing. The role of the middle deltoid is unclear, although it has been suggested that it functions to keep the arm abducted so that it may clear the side of the body.37 Activity in all muscles increases as the speed of gait increases.61 Recent work supports neuronal coordination of arm and leg movement during locomotion. Deitz and colleagues63 and Wannier and colleagues64 reported the behaviors of the arm to leg corresponding to a sys- tem of two coupled oscillators. Results were compatible with the assumption that the proximal arm muscles are associated with the swinging of the arms during gait as a residual function of quadripedal locomotion.

Copyright © 2005 by F. A. Davis. 554 ■ Section 5: Integrated Function Table 14-5 Sagittal Plane Analysis of Stair Ascent (Fig. 14–39): Stance Phase–Weight Acceptance (0%–14% of Stance Phase) through Pull-Up (14%–32% of Stance Phase) Joint Motion Muscle Contraction Hip Extension: 60Њ–30Њ of flexion Concentric Gluteus maximus Knee Extension: 80Њ–35Њ of flexion Semitendinosus Concentric Ankle Dorsiflexion: 20Њ–25Њ of dorsiflexion Gluteus medius Concentric Plantarflexion: 25Њ–15Њ of dorsiflexion Vastus lateralis Concentric Rectus femoris Tibialis anterior Soleus Gastrocnemius ascent and descent can be compared with those during is flexed at the hip, knee, and ankle. During this level-ground walking. The internal knee extensor period, the task is to pull the weight of the body up to moment in both stair ascent and descent was approxi- the next stair level. The knee extensors are responsible mately three times larger than that of level-ground for most of the energy generation required to accom- walking, but the ankle moments were approximately plish PU. The FCN period is from approximately 32% the same. Powers were largely generative in stair ascent to 64% of the gait cycle and corresponds roughly to the and absorptive in descent for all joints. midstance through toe-off subdivisions of walking gait. In the FCN period, the greatest amount of energy is The investigators divided the stance phase of the generated by the ankle plantarflexors. stair gait cycle into the three subphases and the swing phase into two subphases. The subdivisions of the Some of the data regarding joint ROM and muscle stance phase are WA, pull-up (PU), and forward con- activity for ascending stairs that was collected by tinuance (FCN). The subdivisions of the swing phase McFayden and Winter66 are presented in Tables 14-5, are foot clearance (FCO) and foot placement (FP). As 14-6, and 14-7. The tables demonstrate differences can be seen in Figure 14-35, WA comprises approxi- between level-ground gait and stair gait in regard to mately the first 14% of the gait cycle and is somewhat joint ROM, as well as some differences in the muscle comparable to the heel strike throughout the loading activity required. phase of walking gait. However, in contrast to walking gait, the point of initial contact of the foot on the stairs CONCEPT CORNERSTONE 14-4: Differences between is usually located on the anterior portion of the foot Level-Ground Gait and Stair Gait and travels posteriorly to the middle of the foot as the weight of the body is accepted. The PU portion, which Table 14-6 shows that considerably more hip and knee flexion extends from approximately 14% to 32% of the gait are required in the initial portion of stair gait than are required cycle, is a period of single-limb support. The initial por- in normal level-ground walking. Therefore, a patient would tion of PU is a time of instability, inasmuch as all of the require a greater ROM for stair climbing (the same stair dimensions body weight is shifted onto the stance extremity when it Table 14-6 Sagittal Plane Analysis of Stair Ascent (Fig. 14–39): Stance Phase–Pull-Up (End of Pull-Up) through Forward Continuance (32%–64% of the Stance Phase of Gait Cycle) Joint Motion Muscle Contraction Hip Concentric and isometric Extension: 30Њ–5Њ flexion Gluteus maximus Knee Gluteus medius Eccentric Flexion: 5Њ to 10Њ–20Њ of Semitendinosus Concentric Ankle flexion Gluteus maximus Gluteus medius Eccentric Extension: 35Њ–10Њ of Vastus lateralis Concentric flexion Eccentric Rectus femoris Flexion: 5Њ to 10Њ–20Њ of Rectus femoris flexion Vastus lateralis Soleus Plantarflexion: 15Њ of dor- Gastrocnemius siflexion to 15Њ–10Њ of Tibialis anterior plantarflexion

Copyright © 2005 by F. A. Davis. Chapter 14: Gait ■ 555 Table 14-7 Sagittal Plane Analysis of Stair Ascent (Fig. 14-39): Swing Phase (64%–100% of Gait Cycle)—Foot Clearance through Foot Placement Joint Motion Muscle Contraction Hip Concentric Knee Flexion: 10Њ–20Њ to 40Њ–60Њ of flexion Gluteus medius Extension: 40Њ–60Њ of flexion to 50Њ of flexion Concentric Ankle Flexion: 10Њ of flexion to 90Њ–100Њ of flexion Semitendinosus Concentric Extension: 90Њ–100Њ of flexion to 85Њ of flexion Vastus lateralis Rectus femoris Concentric and isometric Dorsiflexion: 10Њ of plantarflexion to 20Њ of dorsiflexion Tibialis anterior and slope) than for normal level-ground walking. Naturally on level ground may not have the ability to run. muscle activity and joint ROMs will change if stairs of dimensions Running requires greater balance, muscle strength, other than the ones investigated by McFayden and Winter are and ROM than does normal walking. Greater balance is used.66 required because running is characterized not only by a considerably reduced base of support but also by an Ascending stairs involves a large amount of positive absence of the double-support periods observed in work that is accomplished mainly through concentric normal walking and the presence of float periods in action of the rectus femoris, vastus lateralis, soleus, and which both feet are out of contact with the supporting medial gastrocnemius muscles. Descending stairs is surface (Fig. 14-36). The walking gait cycle presented in achieved mostly through eccentric activity of the same Figure 14-37 can be used to compare the gait cycle in muscles and involves energy absorption. The support walking with running gait. The percentage of the gait moments during stair ascent, stair descent, and level- cycle spent in float periods will increase as the speed of ground walking exhibit similar patterns; however, the running increases. Muscles must generate greater magnitude of the moments is greater in stair gait, and, energy both to raise HAT higher than in normal walk- consequently, more muscle strength is required. ing and to balance and support HAT during the gait Kirkwood et al.67 found that the maximum peak inter- cycle. Muscles and joint structures also must be able to nal abductor moment at the hip occurred during absorb more energy to accept and control the weight of descending stairs. HAT. Running Gait For example, in normal level-ground walking, the magnitudes of the GRFs at the CoP at initial contact are Running is another locomotor activity that is similar to approximately 70% to 80% of body weight and rarely walking, but certain differences need to be examined. exceed 120% of body weight during the gait cycle.68,69 As in the case of stair gait, a patient who is able to walk However, during running, the GRFs at the CoP have been shown to reach 200% of body weight and increase to 250% of body weight during the running cycle. ᭣ Figure 14-36 ■ Running gait cycle.

Copyright © 2005 by F. A. Davis. 556 ■ Section 5: Integrated Function ᭣ Figure 14-37 ■ Walking gait cycle. Furthermore, the knee is flexed at about 20Њ when the these differences in joint angles from level-ground foot strikes the ground. This degree of flexion helps to walking. At each joint, the maxima for running exceed attenuate impact forces but also increases the forces those of walking. In the case of the hip, only flexion acting at the patellofemoral joint. The base of support range is increased. The knee range in running is not in running is considerably less than in walking. A typi- very different from that in walking, but it takes place in cal base of support in walking is about 2 to 4 inches, approximately 25Њ more flexion. The ankle has greatly whereas in running, both feet fall in the same line of increased dorsiflexion and modestly increased plan- progression, and so the entire center of mass of the tarflexion. body must be placed over a single support foot. To com- pensate for the reduced base of support, the functional The ankle is in about 10Њ of dorsiflexion at heel limb varus angle increases. Functional limb varus angle strike and rapidly dorsiflexes to reach about 25Њ to 30Њ is the angle between the bisection of the lower leg and dorsiflexion. The rapid dorsiflexion is followed imme- the floor.70 According to McPoil and Cornwall,70 the diately by plantarflexion, which continues throughout functional limb varus angle increases about 5Њ during the remainder of the stance phase and into the initial running in comparison with walking. part of the swing phase. Plantarflexion reaches a maxi- mum of 25Њ in the first few seconds of the swing phase. ■ Joint Motion and Muscle Activity Throughout the rest of the swing phase, the ankle dor- siflexes to reach about 10Њ in late swing in preparation Joint Motion for heel strike.69 The ROM varies according to the speed of running and The reference extremity begins to medially rotate among different researchers. Comparisons in joint during the swing phase. At heel strike, the extremity angles, moments, and powers between walking and run- continues to medially rotate and the foot pronates. ning are shown in Figure 14-38.71 At the beginning of Lateral rotation of the stance extremity and supination the stance phase of running, the hip is in about 45Њ of of the foot begins as the swing leg passes the stance flexion at heel strike and extends during the remain- limb in midstance. The ROM in the lower extremities der of the stance phase until it reaches about 20Њ of needed for running, in comparison with the ROM hyperextension just after toe-off.70 The hip then flexes required for normal walking, is presented in Table to reach about 55Њ to 60Њ of flexion in late swing. Just 14-8. The largest differences in the total ROM require- before the end of the swing phase, the hip extends ments between the two activities appear to be at the slightly to 45Њ to 50Њ in preparation for heel strike.58 knee and hip joints. At the knee joint, up to an addi- The knee is flexed to about 20Њ to 40Њ at heel strike and tional 90Њ of flexion is required for running versus walk- continues to flex to 60Њ during the loading response. ing. At the hip joint running requires about twice the Thereafter, the knee begins to extend, reaching 40Њ of amount of motion that was needed for normal walking. flexion just before toe-off. During the swing phase and initial float period, the knee flexes to reach a maximum Muscle Activity of approximately 125Њ to 130Њ in the middle of the swing phase. In late swing, the knee extends to 40Њ in The gluteus maximus and gluteus medius muscles are preparation for heel strike.69 In Figure 14-38, note active both at the beginning of the stance phase and at the end of the swing phase. The tensor fasciae latae muscle is also active at the beginning of stance and at

Sagittal S Joint Angle J HIP 85 N.m/kg 2 20 DEGREES 65 flex ext 1 extension flexion 45 0 25 -1 20 40 60 80 100 -2 5 -3 -15 0 0 KNEE 110 N.m/kg 2 DEGREES flex ext 1 extension flexion 80 0 -1 50 20 40 60 80 100 -2 20 -3 20 -10 0 0 ANKLE 40 N.m/kg 3 DEGREES flex ext 2 plantar dorsiflexion 20 1 0 0 20 40 60 80 -1 20 -2 20 -3 -40 0 0 % Gait Cycle % 557 ▲ Figure 14-38 ■ Sagittal plane joint angles, moments, and powers for running (solid lin Moments are internal moments normalized to body mass, plotted with extensor and plantarflexor negative. The vertical solid line near 40% of gait cycle represents toe-off for running; the vertical do ers for running redrawn from Novacheck TF: The biomechanics of running. Gait Posture 7:77-95,

Sagittal Sagittal Joint Moment Joint Power Watt/kg 15 abs gen 10 40 60 80 100 5 20 40 60 80 100 0 Watt/kg -5 abs gen -10 -15 40 60 80 100 20 40 60 80 100 0 15 10 5 0 -5 -10 -15 0 Watt/kg 15 abs gen 10 40 60 80 5 20 40 60 80 0 -5 -10 -15 0 % Gait Cycle % Gait Cycle ne) and walking (dotted line). Joint angles are plotted with flexion and dorsiflexion positive. r positive. Powers are normalized to body mass, plotted with generation positive and absorption otted line near 60% of gait cycle represents toe-off for walking. (Joint angles, moments, and pow- , 1998, with permission from Elsevier.)

Copyright © 2005 by F. A. Davis. 558 ■ Section 5: Integrated Function Table 14-8 Average Peak ROM at the Hip, Knee the differences in the length of the swing phases in the and Ankle: Comparison between two types of gait. The swing period in walking gait is Running69–71 and Walking8, 71 approximately 40% of the total gait cycle, whereas in running gait, the swing phase constitutes about 62% of Running Walking the total gait cycle. Most of the activity in the tibialis anterior muscle during both walking and running gait Hip joint Hip joint is concentric or isometric action that is necessary to Flexion clear the foot in the swing phase of gait. The longer Flexion 55Њ–65Њ Extension 30Њ swing phase in running accounts for at least part of the 0Њ–20Њ difference in tibialis anterior activity between walking Extension 10Њ–20Њ Knee joint and running gaits. Tibialis anterior activity in the first Flexion 40Њ–50Њ half of the stance phase in running gait accounts for the Knee joint Extension 0Њ remainder of the difference in activity in this muscle. Flexion 80Њ–130Њ Ankle joint 10Њ ■ Moments, Powers, and Energies Dorsiflexion 20Њ Extension 0Њ–5Њ Plantarflexion In Figure 14-38, note the differences in internal moments and powers from walking. In all joints, the Ankle joint moments are greatly increased, particularly the knee extensor moment in early stance. Similarly, all the Dorsiflexion 10Њ–30Њ power generators are greatly increased in running. The chief generators are, again, A2, H3, and H1, but an Plantarflexion 20Њ–30Њ additional source, K2, is now important. Note that the knee extensors in early stance (K2) are important in the end of swing but also is active between early and running. The absorption phases typical of walking are midswing. The adductor magnus muscle shows activity increased at all joints in running. for about 25% of the gait cycle from late stance through the early part of the swing phase. Activity in the iliop- In walking, potential and kinetic energy of the soas muscle occurs for about the same percentage of HAT are out of phase, which results in considerable the gait cycle as the adductor longus muscle, but iliop- energetic savings. In running, these savings cannot soas activity also occurs during the swing phase from occur, but two other methods of gaining efficiency are about 35% to 60% of the gait cycle. present. First, there are storage and return of elastic potential energy by the stretch of elastic structures, par- The quadriceps muscle acts eccentrically during ticularly tendons. Second, there is transfer of energy the first 10% of the stance phase to control knee flex- from one body segment to another by two-joint muscles ion when the knee is flexing rapidly. The quadriceps acting as “energy straps.”71 ceases activity after the first part of stance, and no activ- ity occurs until the last 20% of the swing phase, when Summary concentric activity begins to extend the knee (to 40Њ of flexion) in preparation for heel strike. The medial ham- As a result of the efforts of many investigators, our pres- strings are active at the beginning of stance and ent body of knowledge regarding human locomotion is through a large part of swing. For example, the medial extensive. However, gait is a complex subject, and fur- hamstrings are active from 18% to 28% of the stance ther research is necessary to standardize methods of phase, from about 40% to 58% of initial swing, and for measuring and defining kinematic and kinetic vari- the last 20% of swing. During part of this time, the knee ables, to develop inexpensive and reliable methods of is flexing and the hip is extending, and the hamstrings analyzing gait in the clinical setting, and to augment may be acting to extend the hip and to control the the limited amount of knowledge available regarding knee. During initial swing, the hamstrings are probably kinematic and kinetic variables in the gaits of children acting concentrically at the knee to produce knee flex- and elderly persons that would form databases for ion, which reaches a maximum at midswing. In late movement pathologies. swing, the hamstrings may be contracting eccentrically to control knee extension and to reextend the hip. Standardization of equipment and methods used to quantify gait variables, as well as standardization of A comparison of walking and running muscle activ- the terms used to describe these variables, would help ity at the ankle shows that in walking, gastrocnemius eliminate some of the present confusion in the litera- muscle activity begins just after the loading response at ture and make it possible to compare the findings of about 15% of the gait cycle and is active to about 50% various researchers with some degree of accuracy. Some of the gait cycle (just before toe-off). In running, gas- standardization has been provided by the manufactur- trocnemius muscle activity begins at heel strike and ers of motion analysis systems; as a result, investigators continues through the first 15% of the gait cycle, end- using similar systems tend to use the same conventions. ing at the point at which activity begins in walking. The At the present time, inexpensive, quantitative, and reli- gastrocnemius muscle becomes active again during the able clinical methods of evaluating gait are limited to last 15% of swing. time and distance variables of step length, step dura- The tibialis anterior muscle activity occurs in both stance and swing phases in walking and running. However, the total period of activity of this muscle in walking (54% of the gait cycle) is less than it is in run- ning, in which it shows activity for about 73% of the gait cycle. The difference in activity of the tibialis anterior muscle between walking and running is due partly to

Copyright © 2005 by F. A. Davis. tion, stride length, cadence, and velocity.72 These meas- Chapter 14: Gait ■ 559 ures provide a simple means for objective assessment of a patient’s status and for detecting overall change, but and associates75 reported that the ROMs for flexion and they provide virtually no help in determining treat- extension of the joints of the lower extremities were ment. Increases in step length and decreases in step almost identical to the values obtained for adults. duration may be used to document a patient’s progres- However, linear displacements, velocities, and accelera- sion toward a more normal gait pattern; however, a nor- tions were found to be consistently larger for these chil- mal gait pattern may not be appropriate for many dren than they were for adults.75 Cadence, stride patients. Although many movement practitioners feel length, stride time, and other distance and temporal that it is best to aim for normal gait during early stages variables have been found to show variability until the of rehabilitation, it is also important to identify the child reaches 7 or 8 years of age. A gait pattern that is means by which a person can use the flexibility of the similar to normal adult gait is demonstrated by children human body to compensate for deficiencies.24,44 from 8 to 10 years of age. Automated gait analysis computer programs can pro- vide the clinician with information about all of the kine- Sutherland and colleagues,76 who studied 186 chil- matic and kinetic gait parameters related to a particular dren from 1 to 7 years of age, suggested that the fol- subject or patient. However, the researcher or clinician lowing five gait parameters could be used as indicators must have sufficient knowledge of the kinematics and of gait maturity: duration of single-limb support, walk- kinetics of normal gait to interpret and use the infor- ing velocity, cadence, step length, and the ratio of mation for the benefit of the patient. pelvic span to ankle spread (indicative of base of sup- port). Increases in all of these parameters except for Effects of Age, Gender, cadence are indicative of increasing gait maturity. In Assistive Devices, and Sutherland and colleagues’ study, the duration of Orthoses single-limb stance increased from about 32% in 1-year- olds to 38% in 7-year-olds (normal mean adult value is Age 39%). Walking velocity also increased steadily, whereas cadence decreased with age.76 Beck et al.77 found that Adult gait has been the focus of numerous studies, but time and distance measures and GRF measurements the gait of young children has not received the same depended on speed of gait and age of the child. amount of attention. The relatively few studies of chil- Increases in height and age were the major factors in dren’s gait that have been conducted have shown that determining changes in time and distance measures the age at which independent ambulation begins is with age. Average stride length was 76% of the child’s extremely variable among individuals and that this vari- height at a walking speed of 104 m/sec, regardless of a ability continues throughout the developmental stages child’s age. According to Beck, after 5 years of age, an of walking. Cioni and coworkers73 found that for 25 full- adult pattern in the GRF emerged.77 term infants, the age at which independent walking (ability to move 10 successive steps without support) Studies involving young children are difficult to was attained varied between 12.6 and 16.6 months. In perform and often complicated by the fact that the the first stage of independent walking, none of the 25 child’s musculoskeletal and nervous systems are in vari- toddlers had heel strike, reciprocal arm swinging, or ous stages of development. However, Sutherland and trunk rotation. However, 4 months after attainment of colleagues attempted to provide evaluators with guide- independent walking, 11 of the 25 children had heel lines for assessing children’s gait by developing a group strike, and 16 of the 25 had reciprocal arm swinging of prediction regions for the kinematic motion curves and trunk rotation. in normal gait. A test of the prediction regions indi- cated that they were capable of detecting a high per- The toddler has a higher center of mass than does centage of abnormal motion and therefore could be the adult and walks with a wider base of support, a used as an initial screen to identify deficits in lower decreased single-leg support time, a shorter step extremity function in children.78 length, a slower velocity, and a higher cadence in com- parison with normal adult gait. A study of 3- and 5-year- In contrast to the dearth of gait studies of young old children showed that some relationships between children, the effects of aging on gait have been and these variables were similar to the relationships found continue to be the object of many studies.17,37,79,80 Some in adult gaits.74 For example, as a group, the 3- and 5- of this interest in elderly gait has been prompted by the year-old children showed significant increases in stride large number of hip fractures and falls experienced by length adjusted for leg length, step length, and cadence elderly persons. Fifty percent of elderly people who from a slow to a free speed and from a free to a fast were able to walk before a hip fracture are not able to speed of gait. However, 5-year-olds differed from 3-year- either walk or live independently after the fracture. olds in that they had less variability in step length Furthermore, it is estimated that an elderly person adjusted for height at slow and free speeds.74 In a study experiences at least two falls per year.81 Therefore, that included children from 6 to 13 years of age, Foley many studies are directed toward determining what constitutes normal elderly gait and whether falls are caused by deficits in motor functioning or control or by other deficits that may accompany normal aging. The use of different age groups and levels of activ- ity (sedentary versus active groups) among investigators has made it difficult to draw definitive conclusions about the effects of normal aging. Despite some varia-

Copyright © 2005 by F. A. Davis. 560 ■ Section 5: Integrated Function peak torque and dorsiflexion ROM.84 Bohannon and colleagues85 found that hip flexor strength was one of tions in the literature, gait speed and step or stride the variables that predicted gait speed. These authors length have frequently been reported to be reduced in did not test plantarflexor strength. Lord and associ- elderly persons, and stance phase and double-support ates86 conducted an exercise program for women 60 times increased. Some investigators have found that years of age and older. After the program, the authors elderly persons, in comparison with younger groups, found significant increases in cadence and stride demonstrate a decrease in natural walking speed, length, as well as reductions in stance time, swing time, shorter stride and step lengths, longer duration of and stance duration. Connelly and Vandervoort87 meas- double-support periods, and smaller ratios of swing to ured the effects of detraining (which involved a decline support phases.17,79 Himann and associates79 found that in quadriceps muscle strength) on walking in a group between 19 and 62 years of age, there was a 2.5% to of elderly persons with a mean age of 82.8 years. 4.5% decline in the normal speed of walking per Strength values measured 1 year after the training pro- decade for men and women, respectively. After age 62, gram had declined 68.3%, and the speed of self- there was an accelerated decline in normal walking selected gait declined by 19.5%. speed: that is, a 16% and 12% decline in walking speed for men and women, respectively.79 Winter and associ- Winter14 also reported that push-off work by the ates37 compared fit and healthy elderly subjects with ankle plantarflexors was lower at the same time that young adults and found that the natural cadence in the absorption by the knee extensors was higher. Although elderly subjects was no different from that in young several causal explanations are possible, these adapta- adults but that the stride length of the elderly subjects tions both are conducive to a safer gait pattern. Note, was significantly shorter and the period of double sup- however, that the increased absorption by the knee port was longer in the elderly subjects than in young extensors would also produce a less efficient gait. adults. Blanke and Hageman80 compared 12 young men, age 20 to 32 years, with 12 elderly men, age 60 to Walking is considered to be a measure of inde- 74 years, and found no effects of aging in regard to step pendence, and faster walking speed is associated with length, stride length, velocity, and vertical and horizon- increased levels of independence. A speed that is faster tal excursions of the body’s center of mass. However, than comfortable walking is needed in many instances the ability to generalize Blanke and Hageman’s find- to cross a street. Walking in conjunction with exercise is ings is low because of the small size of their sample. also considered important to help prevent bone loss in Kerrigan and associates82 found that comfortable walk- the proximal femur.67 Although differences of opinion ing speed and stride length were significantly slower have been found regarding gait speed in elderly peo- than in young adults. In a study of fit healthy elderly ple, the consensus of opinion appears to be that, in people, Winter14 found reduced stride length and a sig- general, elderly persons select a free speed that is nificant increase in stance time, which is consistent with slower than the free speed gait of young people; how- attempting to increase stability. He also reported signif- ever, as was shown previously, a slow gait requires a icantly higher horizontal heel velocity at initial contact, greater consumption of energy. which was surprising because the speed was lower than for the young subjects. This increases the potential for Although the particulars vary, it is clear that there slip-induced falls. are both kinematic and kinetic differences in the gait of elderly people. These can stem from two sources: early Differences in kinetic parameters of gait have also degeneration of strength and/or balance control sys- been reported. Lee and Kerrigan83 found significant tem or adaptation to make gait safer. It is likely that differences in kinetic parameters between a group of both are responsible. elderly persons who fell and an elderly control group. Analysis of data demonstrated significantly greater peak Gender torques in the falling group for hip flexion, hip adduc- tion, knee extension, knee varum, ankle dorsiflexion, The research regarding gender differences in gait is and ankle eversion (P Ͻ 0.003 in each comparison). fraught with the same difficulties as found in gait Also, ankle plantarflexion torque was significantly research with regard to age. Variations among meth- decreased in the falling group (P ϭ 0.001). Joint pow- ods, technologies, and subjects used in various studies ers showed different absorption at the knee and ankle make it difficult to come to many conclusions regard- in the falling group. Kerrigan and associates82 also ing the effects of gender. When differences in height, found that older persons, in comparison with younger weight, and leg length between the genders are consid- persons, had reduced plantarflexion power generation, ered, gender differences are not very great. Oberg and reduced plantarflexion ROM, peak hip extension associates88 found significant differences between men ROM, and increased anterior pelvic tilt. The authors and women for knee flexion/extension at slow, normal, suggested that subtle hip flexion contractures and con- and fast speeds at midstance and swing. They found a centric plantarflexor weakness might be causes of the significant increase in joint angles as gait speed joint changes in elderly people. increased. For example, the knee angle at midstance increased from 15Њ to 24Њ in men and from 12Њ to 20Њ in Mueller and coworkers found that plantarflexor women. However, Oberg and coworkers looked at only peak torque and ankle dorsiflexion were interrelated.84 the knee and hip. In another study, the authors looked These authors suggested that walking speed and step length might be improved by increasing ankle flexor

Copyright © 2005 by F. A. Davis. at velocity, step length, and step frequency.17 Gait speed Chapter 14: Gait ■ 561 was found to be slower in women than in men (118 to 134 cm/sec for men and 110 to 129 cm/sec for For her the most important objective was to gain bal- women), and step length was smaller in women than in ance and stability, not to reduce joint forces. men. Kerrigan and associates89 found that women had significantly greater hip flexion and less knee extension Orthoses during gait initiation, a greater internal knee flexion moment in preswing, and greater peak mechanical The function of orthoses in gait is to alter the mechan- joint power absorption at the knee in preswing. Kinetic ics of walking. They are used to support normal align- data were normalized for both height and weight. ment, to prevent unwanted motion, to help prevent These authors also found that women had a greater deformity, to reduce unwanted forces or moments,91–93 stride length in proportion to their height and that they and, more recently, to augment joint power.94 Although walked with a greater cadence than did their male a full discussion is beyond the scope of this book, the counterparts.89 student can deduce the effects of various types of devices with knowledge of the mechanics of gait. In all Assistive Devices cases, the wish is to reduce or prevent unwanted move- ment or undesirable forces while permitting as normal Walking without the use of assistive devices (crutches, mechanics as possible. For example, one may wish to canes, and walkers) is preferred by most people. limit ankle plantarflexion in a child with cerebral palsy. However, such devices often are necessary either after a However, in so doing, one would prefer not to com- lower-extremity fracture, when the healing bone is pletely inhibit the active energy-generating activity of unable to bear full body weight, or as a more perma- the ankle plantarflexors (A2) during push-off. Formerly nent adjunct for a balance, to compensate for muscle relying on solid ankles, more recent hinged orthoses deficiencies or for joint pain. Recall that a very small prevent excessive plantarflexion by use of a posterior force at the hand is needed to produce a large balanc- stop but permit the ankle to move into dorsiflexion in ing moment about the standing leg because of the long late stance, and the child is able to generate some perpendicular distance from the point of application of power through the plantarflexion that follows. Attempts the force on the hand to the hip joint center. This may have also been made to make use of mechanical char- be responsible for the popularity of walkers for elderly acteristics of a leaf-spring design to return energy to the persons, even when they appear to put little weight on foot during push-off. Although good in concept, them. Canes have typically been used on the side con- designs to date have failed to show return of energy.94 tralateral to an affected lower extremity to reduce forces acting at the affected hip, the reason being that C a s e A p p l i c a t i o n 1 4 - 8 : Gait Status at Discharge a lower abductor muscle force on the affected side would be necessary to balance the weight of the upper Recall that Ms. Brown was prescribed an ankle-foot body during single-limb stance if an upwardly directed orthosis to assist with providing an adequate support force was provided by the hand on a cane at some dis- moment during stance phase and to prevent foot drop tance from the hip joint center. Krebs and coworkers90 and the resulting energy-costly hip hiking. However, if tested the effect of cane use on reduction of pressure the orthosis was rigid, it would make it impossible for through the use of an instrumented femoral head pros- her to achieve any A2-S push-off during late stance. thesis that quantified contact pressures at the acetabu- Two options were considered: (1) a hinged orthosis that lar cartilage. The prosthetic head contained 13 permitted unlimited dorsiflexion but had a stop beyond pressure-sensing transducers, which were deflected by 10Њ of plantarflexion, thus allowing limited push-off, and 0.00028 mm/MPa pressure from opposing acetabular (2) a flexible ankle-foot orthosis that narrowed posterior cartilage. The magnitude of acetabular contact pres- to the ankle, thus permitting a limited range of both dor- sure was reduced by 28% on one transducer and by siflexion and plantarflexion. Because it was hoped that 40% on another transducer in cane-assisted gait in use of the device would be temporary, the latter was comparison with unaided gait. The reduction in pres- chosen. Gait reeducation included progressive training sure at the hip coincided with reductions in EMG without the orthosis as strength was gained, and at dis- amplitude in comparison with the same pace in charge, Ms. Brown used her orthosis only for outdoor unaided gait trials. The authors concluded that the use use. As her stability improved, she was able to progress of a cane on the contralateral side apparently allows the from a four-point cane to a straight cane. When she was person to increase the base of support and to decrease discharged from outpatient treatment, she was walking muscle and GRF forces acting at the affected hip. The at 0.55 m/sec. hip muscle abductor force was reduced, and gluteus maximus activity was reduced approximately 45%. The Abnormal Gait maximum GRF during cane-assisted gait occurs between heel strike and midstance. Both quantitative and qualitative evaluations of gait are useful for assessors of human function. The most Recall that Ms. Brown used a four-point cane on important quantitative variable is gait speed, which has her unaffected side, because her arm was also affected. been shown to be related to all levels of disablement.95

Copyright © 2005 by F. A. Davis. 562 ■ Section 5: Integrated Function the normal patterns of transformation from potential to kinetic energy and redistribution between segments An individual’s gait pattern may reflect not only physi- are disturbed. Increases in muscle activity used to com- cal or psychological status but also any defects or pensate for these disturbances may lead to increases in injuries in the joints or muscles of the lower extremi- the amount of oxygen that is consumed. In a compari- ties. In assessing an abnormal gait, it is helpful to clas- son between patients who had an ankle fusion and sify the cause or causes of deviations into one or more patients who had a hip fusion, oxygen consumption for of the following four causal categories: structural patients with the hip fusion was 32% greater than nor- impairment, functional impairment, functional pain, mal and greater than in patients with the ankle or compensation/adaptation. Definitions and exam- fusion.100 ples follow. Functional Impairment Structural Impairment This group includes all causes in which the timing These are structural malformations that are congenital, and/or amplitude of muscle activity is abnormal. caused by injury, or caused by structural changes occur- ring secondary to these. Certain disease conditions such as Parkinson’s dis- ease produce characteristic gaits that are easily recog- A common structural abnormality is leg length dis- nized by a trained observer. The parkinsonian gait is crepancy. Kaufman and coworkers96 undertook a study characterized by an increased cadence, shortened to determine the magnitude of limb length inequality stride, lack of heel strike and toe-off, and diminished that would result in gait abnormalities. Many minor arm swinging. The muscle rigidity that characterizes limb inequalities are found in the general population this disease interferes with normal reciprocal patterns but many of these do not necessitate any particular of movement.101 treatment or intervention because they do not have any significant effects on normal gait. The authors con- When the plantarflexors, which are the major cluded that a limb length discrepancy of 2.0 cm source of mechanical energy generation in gait, are resulted in an asymmetrical gait and had the potential unable to generate sufficient power, muscles at other for causing changes in articular cartilage. Song and col- joints must provide more energy than in normal gait.3 leagues97 evaluated neurologically normal children For example, Winter102 found that individuals with who had limb discrepancies of 0.8% to 15.8% of the below-knee amputations used the gluteus maximus, length of the long extremity (0.6 to 11.1 cm). The com- semitendinosus, and knee extensor muscles as energy pensatory strategies observed were equinus position of generators to compensate for loss of the plantarflexors. the ankle and foot of the short limb (toe walking), Olney and associates32 found that in children who had vaulting over the long limb, increased flexion of the unilateral plantarflexor paralysis, the involved plan- long limb, and circumduction of the long limb. tarflexors produced only 33% of the energy generation, Children who used toe walking had a greater vertical in comparison with the 66% produced in normal gait. translation of the body’s center of mass during gait than did normal controls. Paralysis or paresis of the plantarflexors (gastroc- nemius, soleus, flexor digitorum longus, tibialis poste- Structural problems may be implicated in running rior, plantaris, and flexor hallucis longus muscles) injuries. Increases in the Q-angle, tibial torsion, and results in a calcaneal gait pattern.103 This pattern is pronation of the foot may contribute causes to characterized by greater than normal amounts of ankle patellofemoral syndromes. In running, stresses are dorsiflexion and knee flexion during stance and a greater than in walking, and so there is an accompany- shorter-than-normal step length on the affected side. ing increase in the likelihood of injury. In a survey of The abnormal amount of knee flexion and the fact that the records of 1650 running patients between the years the soleus muscle is not pulling the knee into extension 1978 and 1980, 1819 injuries were identified.98 The necessitate a higher level of quadriceps activity to stabi- knee was the site most commonly injured in running, lize the knee during the stance phase. The period of and patellofemoral pain was the most common com- single-limb support is shortened because of the diffi- plaint. culty of stabilizing the tibia and the knee. Step length is shorter than normal because the normal push-off seg- At the foot, pes cavus and pes planus cause alter- ment of gait is eliminated. The normal heel-off and ations in weight and may cause abnormal stresses at the progression to toe-off are changed into a rather abrupt hip or knee. In pes cavus, the weight is borne primarily liftoff of the entire foot. The asymmetry of this type of on the hindfoot and metatarsal regions, and the mid- gait pattern is obvious through observation and a com- foot provides only minimal support.99 In running, the parison of right and left step lengths. metatarsals bear a disproportionate share of the weight. In pes planus, the weight is borne primarily by the mid- Sometimes an isolated weakness or paralysis of a foot rather than being distributed among the hindfoot, single muscle will produce a characteristic gait. For lateral midfoot, metatarsals, and toes, as it is in the nor- example, a unilateral paralysis of the gluteus medius mal walking foot. The propulsive phase of gait is results in a typical gait pattern called a gluteus medius severely compromised. gait. The characteristics of this gait pattern can be deduced by reviewing the function of the gluteus Disturbances in the normal gait pattern usually cause increases in the energy cost of walking because

Copyright © 2005 by F. A. Davis. medius during normal gait. Normally, the gluteus Chapter 14: Gait ■ 563 medius stabilizes the hip and pelvis by controlling the drop of the pelvis during single-limb support, especially tact; (2) to control the external plantarflexion moment at heel strike; during the first part of the stance phase. If gluteus (3) to dorsiflex the foot in initial swing; and (4) to maintain the ankle medius activity on the side of the stance leg is absent, in dorsiflexion during midswing and terminal swing. If these func- the pelvis, accompanied by the trunk, will fall exces- tions are absent, the following would be expected to occur: (1) the sively on the swing side, which results in a loss of bal- entire foot or the toes would strike the floor at initial contact; (2) ance. To prevent the trunk and pelvis from falling to entry into stance phase would be abrupt; (3) the amount of flexion the unsupported side and to maintain HAT over the at the hip and knee would have to increase to clear the foot in ini- stance leg, the individual compensates by laterally tial swing; and (4) a method of either shortening the swing leg or bending the trunk over the stance leg. The trunk lengthening the stance would have to be found to clear the plan- motion enables the person to maintain balance by tarflexed joint. keeping the center of mass over the base of support and allows the swing leg to be lifted high enough to clear In patients with bilateral lower extremity paralysis, the ground. The trunk motion reduces the moment walking usually involves the use of long leg braces and arm of gravity, thus reducing the need for hip abductor crutches. In this form of gait, the trunk and upper contraction and the concomitant compression caused extremity muscles must perform all of the work of walk- by the hip abductors. The lateral trunk lean character- ing, and the energy cost of walking is much greater than izes the gluteus medius gait. The use of an assistive normal. A form of electrical stimulation called func- device such as a cane on the side opposite to the para- tional neuromuscular stimulation (FNS) is currently lyzed muscle reduces the need for the lateral trunk being used to activate the paralyzed lower extremity lean. The use of a cane decreases the energy required muscles so that these muscles can generate energy for in a gluteus medius gait, although it remains above that walking. However, the energy cost of FNS walking is still of normal gait. well above that of normal gait.104 The gluteus maximus in normal gait provides for ■ Pain stability in the sagittal plane and for restraint of forward progression. This muscle helps to counteract the exter- This group includes all causes of variations that are nal flexion moment at the hip in the early part of stance attributable primarily to pain. All overuse injuries fall and restrains the forward movement of the femur in into this category. late swing in normal gait. When the gluteus maximus is paralyzed, the trunk must be thrown posteriorly at heel Iliotibial band syndrome and popliteal tendonitis104 strike, to prevent the trunk from falling forward when experienced by runners are common. Plantar fasciitis, there is an external flexion moment at the hip. The caused by repetitive stretching of the planter fascia backward lean is typical of a gluteus maximus gait. between its origin at the plantar rim of the calcaneous and its insertion into the metatarsal heads, is a common The quadriceps is normally active at initial contact overuse syndrome seen in young athletes.105 Many gait throughout early stance when there is an external flex- variations can be seen in osteoarthritis.106 ion moment acting at the knee. It is common for peo- ple with patellar pain to inhibit quadriceps contraction. Pain also appears to be a factor leading to an in- Its function is easily compensated for if a person has crease in oxygen consumption. As pain increases, oxy- normal hip extensors and plantarflexors. The gluteus gen consumption has been found to increase.107 maximus and soleus muscles pull the femur and tibia, respectively, posteriorly, which results in knee exten- ■ Adaptation/Compensation sion. Additional compensation may be accomplished by forward trunk bending and a rapid plantarflexion after This group includes all causes of variations that occur initial contact. The forward shifting of the weight cre- when one lower extremity has a structural or functional ates an external extension moment at the knee (at ini- impairment and the other (normal) extremity com- tial contact and during the loading response period). It pensates by adapting its gait pattern. The human body also places the knee in hyperextension and eliminates is remarkable in its ability to compensate for losses or the need for quadriceps activity. If both the quadriceps disturbances in function. Most of the compensations and the gluteus maximus are paralyzed, a person may that are made are performed unconsciously, and if the compensate for the loss by pushing the femur posteri- disturbance is slight, such as occurs in excessive prona- orly with his or her hand at initial contact. The arm sup- tion of the foot, the individual may not be aware that ports the trunk; it prevents hip flexion and also thrusts the gait pattern is in any way unusual. However, most the knee into extension. compensations will result in an increase in energy expenditure over the optimal amount and may result in CONCEPT CORNERSTONE 14-5: Paralysis excessive stress on other structures of the body. of Dorsiflexors Asymmetries of the lower extremities that result The normal functions of the dorsiflexors in gait are (1) to maintain in gait adaptations may have structural or functional primary causes, such as contractures of soft tissues the ankle in neutral so that the heel strikes the floor at initial con- around the joints, bony ankylosis, and muscle weakness or spasticity.

Copyright © 2005 by F. A. Davis. 564 ■ Section 5: Integrated Function Many compensations for inadequate power genera- tion have been identified.44 For example, persons with Example 14-3 hemiparesis resulting from stroke frequently show greater than normal power generation from ankle plan- One might see excessive plantarflexion during stance tarflexors at push-off (A2-S) of the unaffected limb phase in a limb that is normal. The primary cause could (interlimb compensation) or in hip extensors in early be in the other limb: for example, an inability to clear stance (H1-S) on the affected side (intralimb compen- the toes in swing phase as a result of inadequate knee sation). flexion. The excessive plantarflexion would be an adap- tation. Example 14-4 Summary A somewhat different example of adaptation could The objectives of gait analysis are to identify deviations result from a knee flexion contracture. When the from normal and their causes. Once the cause has been affected extremity is weight-bearing, the normal extrem- determined, it is possible to take corrective action aimed ity will be proportionately too long to swing through in at improving performance, eliminating or diminishing a normal manner. A method of equalizing leg lengths is abnormal stresses, and decreasing energy expenditure. necessary for the swing leg to swing through without hit- Sometimes the corrective action may be as simple as ting the floor. Excessive plantarflexion during push-off using a lift in the shoe to equalize leg lengths or develop- of the affected side, described previously, would be one ing an exercise program to increase strength or flexibility means. In this case, there is no structural or functional at the hip, knee, or ankle. In other instances, corrective abnormality in the adaptive movement. Alternatively, action may require the use of assistive devices such as the person could increase the amount of flexion at the braces, canes, or crutches. However, an understanding of hip, knee, and ankle of the unaffected side. Again, the the complexities of abnormal gait and the ability to detect limb showing the adaptation has no structural or func- abnormal gait patterns and to determine the causes of tional impairment. Other methods that produce relative these deviations must be based on an understanding of shortening of the swinging leg are hip hiking, or cir- normal structure and function. The study of human gait, cumduction of the leg. Each of these compensations like the study of human posture, illustrates the interde- makes it possible to walk, although they increase the pendence of structure and function and the large variety energy requirements above normal levels. of postures and gaits available to the human species. Study Questions 1. The stance phase constitutes what percentage of the gait cycle in normal walking? How does an increase in walking speed affect the percentage of time spent in stance? 2. What percentage of the gait cycle is spent in double support? How is double support affected by increases and decreases in the walking speed? 3. Describe the subdivisions of the stance and swing phases of the walking gait cycle, using the tra- ditional terminology. 4. How do the traditional phases of gait used to describe walking gait compare with the RLA terms? Describe the similarities and differences between the terms. 5. Maximum knee flexion occurs during which period of the gait cycle? 6. What are the approximate values of maximum flexion and extension required for normal gait at the knee, hip, and ankle? 7. How does the total range of motion required for normal gait at the knee, hip, and ankle com- pare with the range of motion required for running and stair gait? 8. What is the difference between an internal moment and an external moment? 9. What is the concept of the support moment, and what major muscle groups are responsible? 10. What moments are acting at the ankle, knee, and hip at initial contact? Answer the same ques- tion with regard to different gait events: foot flat, midstance, heel-off, toe-off. 11. What is largely responsible for the abductor moment at the knee in stance phase? 12. What are the roles of the hamstrings in normal gait? Do they contribute to support and/or to power? 13. What are the major muscle groups that contribute to the positive work of walking, and when in the gait cycle do their contributions occur?

Copyright © 2005 by F. A. Davis. Chapter 14: Gait ■ 565 14. Why does walking faster than normal and walking slower than normal usually result in increased energy costs? 15. Why do long double-support times usually result in increased energy costs? 16. What is the role of the tibialis posterior muscle during walking gait? 17. What is the function of the plantarflexors during walking gait? 18. Describe the transverse rotations in the frontal plane at the pelvis, femur, and tibia during walk- ing gait. 19. Describe the motion of the rearfoot segment with respect to the lower leg in stance phase in the frontal plane. 20. What are the functions of the dorsiflexors in normal walking gait? 21. How is the swinging motion of the upper extremities related to movements of the trunk, pelvis, and lower extremities during walking gait? 22. Compare muscle action in walking gait with muscle action in running gait. 23. Explain what would happen in walking and running if a person’s plantarflexors were weak. What compensations might you expect? References 1. Steindler A: Kinesiology. Springfield, IL, Charles C 2nd ed. Waterloo, Ontario, Waterloo Biomechan- Thomas, 1955. ics, 1991. 15. Finley FR, Cody KA: Locomotive characteristics of 2. Winter DA: Energy assessments in pathological urban pedestrians. Arch Phys Med Rehabil 51:423, gait. Physiother Can 30:183, 1978. 1970. 16. Kadaba MP, Ramakrishnan HK, Wootten ME: 3. Rose J, Gamble JG (eds): Human Walking, 2nd ed. Measurement of lower extremity kinematics during Philadelphia, Williams & Wilkins, 1994. level walking. J Orthop Res 8: 383, 1990. 17. Oberg T, Karznia A, Oberg K: Basic gait parame- 4. Rowe PJ, Myles CM, Walker C, et al.: Knee joint ters: Reference data for normal subjects 10–79 kinematics in gait and other functional activities years of age. J Rehabil Res Dev 30:210, 1993. measured using flexible electrogoniometry: How 18. Drillis R: The influence of aging of the kinematics much knee motion is sufficient for normal daily of gait. In The Geriatric Amputee (National life? Gait Posture 12:143, 2000. Academy of Sciences–National Research Council [NAS-NRC] Publication No. 919). Washington, 5. Sutherland DH: The evolution of clinical gait analy- DC, NAS-NRC, 1961. sis. Part I: Kinesiological EMG. Gait Posture 14:61, 19. Crowinshield RD, Brand RA, Johnston RC: Effects 2001. of walking velocity and age on hip kinematics and kinetics. Clin Orthop 132:140, 1978. 6. Sutherland DH: The evolution of clinical gait 20. Larsson LE, Odenrick P, Sandlund B, et al.: The analysis. Part II: Kinematics. Gait Posture 16:159, phases of stride and their interaction in human 2002. gait. Scand J Rehabil Med 12:107, 1980. 21. Wernick J, Volpe RG: Lower extremity function. In 7. Winter DA: Biomechanics of normal and patholog- Valmassy RI (ed): Clinical Biomechanics of the ical gait: Implications for understanding human Lower Extremities. St. Louis, CV Mosby, 1996. locomotor control. J Motor Behav 21:337, 1989. 22. Hausdorff JM, Purdon PL, Peng CK, et al.: Fractal dynamics of human gait: Stability of long-range cor- 8. Pathokinesiology Service and Physical Therapy relations in stride interval fluctuations. J Appl Department at Rancho Los Amigos National Physiol 80:1448, 1996. Rehabilitation Center: Observational Gait Analysis. 23. Sekiya N, Nagasaki H, Ito H, et al.: Optimal walking Downey, CA, Los Amigos Research and Education, in terms of variability in step length. J Orthop Inc., 2001. Sports Phys Ther 26:266, 1997. 24. Winter DA, Eng JJ, Isshac MG: A review of kinetic 9. Elble RJ, Cousins R, Leffler K, et al.: Gait initiation parameters in human walking. In Craik RL, Otis by patients with lower-half parkinsonism. Brain CA (eds): Gait Analysis: Theory and Application. 119:1705, 1996. St. Louis, Mosby–Year Book, 1994. 25. Eng JJ, Winter DA: Kinetic analysis of the lower 10. Hesse S, Reiter F, Jahnke M, et al.: Asymmetry of limbs during walking: What information can be gait initiation in hemiparetic stroke subjects. Arch gained from a three dimensional model? J Phys Med Rehabil 78:719, 1997. Biomech 28:753, 1995. 11. Lamoreaux LW: Kinematic measurements in the study of human walking. Prosthet Res 69:3, 1971. 12. Murray MP: Gait as a total pattern of movement. Am J Phys Med 46:1, 1967. 13. Murray MP, Drought AB, Kory RC: Walking pat- terns of normal men. J Bone Joint Surg Am 46:335, 1964. 14. Winter DA: The Biomechanics and Motor Control of Human Gait: Normal, Elderly and Pathological,

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Copyright © 2005 by F. A. Davis. Index Note: Page numbers followed by the letter f refer to figures; those followed by the letter t refer to tables. A in shoulder complex, 260–262, Angle of torsion, 357 261f of femur, 358–361, 360f–361f A (anisotropic) band, 115, 115f of glenohumeral joint, 246 Abdominal muscles, 206, 207f, 208 internal and external rotation in, Abduction, 9 239, 240f Angle of Wiberg, 357 Anisotropic materials, 83 of ankle-foot complex, 438, 439f upward/downward rotation, Ankle joint, 440–445, 440f of elbow complex, 298, 299f 241–242, 241f of hip, 376 articulating surfaces of, 440–441, of metatarsophalangeal joints, stress tolerance of, 242 440f Acromioclavicular ligament, 238 462–463, 463f Actin, 114, 115f axis of, 443, 444f Abductor digiti minimi muscle, 473t Action potential, 115 capsule of, 441 Abductor hallucis muscle, 473t Active contraction, of extensor muscles, function of, 443–445, 445f Abductor pollicis brevis muscle, 339 Abductor pollicis longus muscle, 317, 331 normal, deviations from, 472–473 Adduction, 9 gait affecting, 541t, 542t 318f in standing posture analysis, 488, Acceleration, 10. See also Dynamics. of ankle-foot complex, 438, 439f of elbow complex, 298, 299f 488f angular, 37–38, 37f of hip, 375 kinematics and kinetics of, 534 with changing torques, 46 of metatarsophalangeal joints, ligaments of, 441–442, 442f–443f muscles of, 468–472, 469f–471f in gait cycle, 522 462–463, 463f structure of, 440–443 in joint distraction, 29 Adductor brevis muscle, 375 Newton’s law of, 20 Adductor hallucis muscle, 473t normal, deviations from, 472–473 Accessory processes, of lumbar verte- Adductor longus muscle, 375 Ankle synergy, 482 brae, 167 Adductor magnus muscle, 375 Ankle-foot complex, 437–474. See also Acetabular anteversion, 360, 361f Adductor pollicis muscle, 339 Acetabular fossa, 357 Adolescent idiopathic scoliosis, 501, Ankle joint; Foot; Interphalangeal Acetabular labrum, 357–358 joint(s); Metatarsophalangeal damage to, 358 502, 502f joint(s); Subtalar joint; in aging hip, 358 Age (aging), effects of, 136 Tarsometatarsal joint(s); Transverse Acetabular ligaments, transverse, 357 tarsal joint. Acetabular notch, 357 on chest wall structure and function, deviations in, 472–473 Acetabular retroversion, 360, 361f 210 motions of, 438–439, 439f Acetabulum, 356–357, 356f anteversion on, 357 on elbow complex, 296–297, 296t terminology used in, 439–440 center edge angle of, 357, 357f on gait, 559–560 muscles of, 468–472, 469f motion of femur on, 366–367, 367f on posture, 509–511, 509t, 510f overview of, 437–438, 438f Achilles tendon, 469 on rib cage, 210 Ankle-foot orthosis, effect of, on gait, Acromioclavicular joint, 237–242 on temporomandibular joint, 536 articulating surfaces of, 238, 238f Annular ligaments, 289, 289f, 291 capsule of, 238, 238f 225–226 Annular pulleys, 327 degenerative changes of, 258 on vertebral column, 187–188 Annulus fibrosus, 146f, 147 disk of, 238 Aggrecan, 74, 75f function of, 155t dislocation of, classification of, 242 Agonist, muscle, 129 Antagonist, muscle, 129 hypomobility of, 263 contraction of, 129–130, 130f contraction of, 129–130, 130f ligaments of, 238–239, 238f–239f Alar ligaments, 151t, 159, 159f Antalgic gait, 382. See also Gait. motion of, 239–242 Alignment, of tibiofemoral joint, Anteromedial band, 403 395–397, 396f Anteroposterior axis, of body, 7, 7f anterior and posterior tipping in, Alpha motor neuron, 117, 118f Anteversion, acetabular, 360, 361f 239–241, 241f Anconeus muscle, 281, 281f Anti-deformity position, of hand splint- Angle of acetabular anteversion, 357 ing, 325, 325f Angle of inclination, 357 Apical ligaments, 159, 159f of femur, 358, 359f–360f of glenohumeral joint, 246 569

Copyright © 2005 by F. A. Davis. 570 ■ Index Arch(es) of transverse tarsal joint, 454, radial, 327 carpal, 319 455f–456f structure of, 80 cervical vertebral, 159–160 trochanteric, 375, 377, 377f coracoacromial, 250, 252, 252f Axis of rotation, instantaneous, 101 ulnar, 326 lumbar vertebral, 166–167, 167f Bursitis, 430 neural, 143–144, 143f B palmar, 320–321, 321f C plantar, 464–468. See also Plantar Back, low. See Low back. arches. Ball-and-socket joint, 97, 98f Cadence, in gait, 523 thoracic vertebral, 164–165 Base of support (BoS), 16, 17–18, Calcaneal gait, in paralysis/paresis, 562 variations in, 153t Calcaneocuboid joint, 454 17f–18f Calcaneocuboid ligament, 454 Arcuate ligaments, 201, 202f, 402, 407t in static and dynamic postures, 480, Calcaneofibular ligament, 442, 442f Arms, movement of, through space, Calcaneovalgus, 439f 480f Calcaneovarus, 439f 371–372, 371f Bending forces, 84, 154–155 Calcaneus, 438f, 440f Arthritis, degenerative, of hip, 386 Bending moments, 39, 39f Camper’s chiasma, 325, 327f Arthrokinematics, 99–102, 100f–101f Biaxial joints, 96–97 Cancellous (spongy) bone, 82 Arthrosis, of hip, 386 Biceps brachii muscle, 280, 286–287, Cane(s) Articular cartilage. See Hyaline cartilage. Articular congruence, of hip, 361–362, 287f, 292 effect of, on gait, 561 in glenohumeral stabilization, 257, use of 361f Articular disk, 289, 290 257f contralateral, 383–385, 383f Biceps femoris muscle, 376, 403, 414 ipsilateral, 382–383 of temporomandibular joint, Bifurcate ligaments, 452, 453f Capitulotrochlear groove, 274, 274f 217–218, 218f Bilaminar retrodiskal pad, 218 Capitulum, 274, 274f Bilateral stance, 378–379. See also Capsuloligamentous tension, at hip displacement of, 227 joint, 364 in mandibular elevation and Stance. Cardinal planes, of body, 7–8, 7f–8f calculating hip joint compression, Carpal ligaments depression, 220–221 dorsal, 311, 311f Articular eminence, of temporal bone, 379 volar, 310–311, 311f Biomechanical principles, 4–5, 5f Carpal tunnel, 320, 320f 215, 216f Bipennate muscles, 121 Carpal tunnel syndrome, 320 Articular processes, 144f, 145 Blood supply, to femoral head, 363 Carpometacarpal joint(s) Articulating surfaces Body of fingers, 319–321, 319f of thumb, 97, 337–338, 337f of acromioclavicular joint, 238, 238f anatomic positions of, 7, 7f function of, 337–338 of ankle joint, 440–441, 440f cardinal planes of, 7–8, 7f–8f osteoarthritis of, 338, 338f of glenohumeral joint, 246–247, center of gravity of, 16, 16f range of motion of, 320 malalignment of, possible effects of, structure of, 337 247f–248f Carpus. See Wrist complex. of hip 496t Carrying angle, of humeroulnar joint, Body segments, alignment of, in sagittal 284, 284f distal, 358–361, 358f–361f Cartesian body coordinates, 7, 7f proximal, 356–358, 356f–357f plane, 492, 493t Cartilage of humeroradial joint, 276, 277f–278f Bone. See also Osteo- entries; named bone, costal, 194f of humerus, 274, 274f increased/decreased load on, effects of ilium, 173, 173f e.g., Femur. of, 104t of patellofemoral joint, 421–422, 422f architecture of, 82 properties of, 90 of radioulnar joint, 290, 290f cancellous (spongy), 82 response of, to exercise, 105 of radius and ulna, 275, 275f–276f cortical (compact), 82 structure of, 78t, 80–81, 80f of sacrum, 173, 173f effects of immobilization on, types of, 80 of sternoclavicular joint, 234–235, wedges of (menisci, disks, plates, 235f 103–104, 104t labra), 91 Articulation(s). See Joint(s). properties of, 89 Cartilaginous joints, 92–93, 93f Assisted devices, effect of, on gait, 561 response of, to exercise, 105 Cavus foot, 449 Atlantal cruciform ligaments, 158, 159f structure of, 78t, 81–83 Cells. See also specific cell. Atlantoaxial joint, 157, 157f, 162 trabecular systems in, 365, 366f of connective tissue, 72–73, 72t Atlanto-occipital joint, 157, 157f, 162, zone of weakness in, 366, 366f Center of gravity (CoG), 15, 15f, 480 162f Bone-tendon junction, 79, 79f and stability, 17–18, 17f–18f Atlas (C1), 156–157, 157f Boston Scoliosis Brace, 208, 208f in moment arm, 48, 49f Autonomic (terminal) rotation, of knee Boundary lubrication, of joints, 95, 95f location of, 18–19, 19f joint, 413 Bow legs (genu varum), 396, 500, 500f low, 18, 18f Avascular necrosis, of lunate, 309, 309f Brachialis muscle, 280, 286 of head-arms-trunk segment, 16–17, Avulsion, 87 Brachioradialis muscle, 280, 287 16f–17f Axial rotations, of tibiofemoral joint, Breast cancer, treatment of, 267 of human body, 16, 16f 412 Breathing segmental, 15–16, 15f Axis (C2), 157, 157f chest wall components during, coor- Axis of motion of ankle joint, 443, 444f dination and integration of, of ankle-foot complex, 438–439, 439f 208–209 of elbow complex, 282–284, tidal, 201–202, 203f 282f–284f ventilatory sequence during, 208–209 of radioulnar joint, 292–293, 292f Bruxism, 226 of subtalar joint, 447, 448f Bursae of tarsometatarsal joints, 458–459 glenohumeral, 252 in finger flexion, 326–327 of knee joint, 408–409, 408f

Copyright © 2005 by F. A. Davis. Index ■ 571 Center of mass (CoM), in static and protraction/retraction of, 237 specific type of, 77–83 dynamic postures, 480 rotation of, anterior/posterior, 237 bone as, 78t, 81–83 Claw toes, 493–494, 494f bursae as, 80 Center of pressure (CoP), in gait, 528, Clawing, 330, 330f cartilage as, 78t, 80–81, 80f 528f Click, reciprocal, in temporomandi- ligaments as, 77–78, 78t bular joint, 227 tendons as, 78–80, 78t, 79f Center of rotation (CoR), 6 Closed–chain hip function, 372–373, instantaneous, 7 373f, 374t structure of, 72–77 Coccygeal spine (coccyx), 142, 142f viscoelasticity of, 87 Center-edge angle, of acetabulum, 357, Coccygeus muscles, 186–187 Conoid ligaments, 238, 238f 357f Coefficient of kinetic friction, 34 Contractile proteins, in muscle fibers, Coefficient of static friction, 33 114, 114f–115f Central band, 291 Collagen Contractile unit, of muscle, 115–117 Central nervous system, in posture con- in bone, 82 cross-bridge interaction in, 115, 116f in cartilage, 80–81 organization of, 115 trol, 481 in ligaments, 77 types of contraction in, 115–117, 116f Cervical ligaments, 446, 447f in tendons, 78 Contraction, active, of extensor mus- Cervical spine, 142, 142f. See also types of, 74–77, 76f, 76t cles, 331 Collateral ligaments, 322–323, 461 Contracture(s), 99 Vertebral column. lateral, 279–280, 279f, 403, 403f, 441 Coordinated motions, of femur, pelvis, articulations in, 157, 157f medial, 278–279, 279f, 398, 398f, and lumbar spine, in hip function, configuration of, in standing, 492 371–373, 371f–373f, 374t craniovertebral, 156–157, 157f 402–403, 402f, 441, 442f Coracoacromial arch, 250, 252, 252f function of, 161–164 radial, 310, 311f Coracoclavicular ligaments, 238, 238f intervertebral disk in, 160, 160f ulnar, 307, 310, 311f Coracohumeral ligaments, 248, 250f kinematics of, 161–164, 162f–163f Compartment muscles Coronal axis, of body, 7, 7f kinetics of, 164 anterior, 471–472 Coronal plane, in standing posture, ligaments in, 157–159, 158f–159f lateral, 471, 471f lower, 159–160, 160t posterior, 468–471, 470f–471f alignment in Compensatory posture, 493. See also anterior aspect, 498t interbody joints of, 161, 161f Posture. posterior aspect, 499t structure of, 156–161, 156f Compliance, 86, 203 Coronal suture, 91, 91f temporomandibular joint relation- Compression forces Coronary ligaments, 398 joint, 30–31, 31f Coronoid fossa, 274, 274f ship with, 223–225, 224f spinal Coronoid process, 216f, 217 variations in, 153t Cortical (compact) bone, 82 vertebra of axial, 154 Cosine law, for triangles, 23, 23f in lumbar region, 172 Costal cartilage, 194f arches of, 159–160 Compression injury, effects of, on elbow Costochondral joints, 194f, 197–198 atlas (C1), 156–157, 157f complex, 297, 297f–298f Costoclavicular ligaments, 235 axis (C2), 157, 157f Compressive load, on spine, in sitting Costosternal ligaments, 198 body of, 159, 160f posture, 505–506, 505f–506f Costotransverse joints, 165, 197, typical, 159–160, 160f Concentric contraction, of muscle, 116, 197f–198f zygapophyseal joints of, 161 116f, 126, 127f Costotransverse ligaments, 197, Chest wall. See also Rib cage. Concurrent force system, 22–24, 197f–198f components of, coordination and 22f–24f Costovertebral joints, 165, 196–197 integration, during breathing, Condyle(s) Counternutation, 174, 175f 208 mandibular, 216–217, 216f–217f Coupled motions, of tibiofemoral joint, radiation to, 267 occipital, 156, 156f 414 structure and function of Connective tissue Coupling, definition of, 150 developmental aspects of, 209–210 age-related changes of, 136 Coxa valga, 358, 360f, 387 in adult, 209, 209f cells of, 72–73, 72t Coxa vara, 358, 360f, 387 in elderly, 210 classes of, 72f Coxofemoral joint. See Hip joint. in neonate, 209–210, 209f dense, composition of, 78t Creep, 87–88, 88f pathologic changes in, 210–212, effect of exercise on, 104–106 effect of, on low back, 155 extracellular matrix of, 73–77 of intervertebral disks, 154 211f fibrillar component in, 74–77, 76f, Crimp, of collagen fibers, 76 Chiasma, camper’s, 325, 327f Cross-bridge interaction, 115, 116f Children 76t Cross-eyed patella, 500, 501f interfibrillar component in, 73–74, Cruciate ligaments gait in, 559 anterior, 398, 398f, 403–405, postural control in, 509, 509t 73t, 74t, 75f, 75t Chondroblasts, 72, 72t, 80 increased/decreased load on, effects 403f–405f Chondrocytes, 72–73, 80 deficiency of, muscular conse- Chondroitin sulfate, 74, 74t of, 103–104, 104t Chondronectin, 74, 80 mechanical behavior of, 83–87, quences of, 418 Chondrosternal joints, 93, 93f, 198 injury to, 405, 406f Chopart joint. See Transverse tarsal 84f–86f posterior, 398, 398f, 403f, 405 joint. muscular, organization of, 121–122, role of, in flexion/extension, Chronic obstructive pulmonary disease, 410–411, 410f–411f 121f–122f Cruciate pulleys, 327 202 properties of, 83–90 Cubitus valgus, 284, 284f in chest wall structure and function, in specific tissues, 89–90 210–212, 211f time-dependent and rate- resting position of diaphragm in, dependent, 87–89, 88f 204f Clavicle, 234f. See also Acromioclavicular joint; Sternoclavicular joint. elevation/depression of, 236–237, 236f

Copyright © 2005 by F. A. Davis. 572 ■ Index Cubitus varus, 284, 284f goals and basic elements of, Entheses, 77, 79 Cuboid bone, 438f 481–484 inflammation at, 286 Curvilinear motion, 6–7 Cylindrical grip, 341–343, 342f Dynamic state, 20 Entrapment, meniscal, 411 Dynamics, 19–20. See also Acceleration. Epicondylalgia, lateral, 278 D Dysplastic hip, 388 Epicondylitis, lateral (tennis elbow), Deceleration, in gait cycle, 522 articular contact in, 361–362, 362f 281, 298 Deep tendon reflex, 134 range of motion of, 367–368, 368f diagnosis and treatment of, 299 Degenerative arthritis, of hip, 386 muscle and tendon changes in, 281t Degenerative disorders, of temporo- E Epimysium, 121, 121f Epitenon, 78 mandibular joint, 227 Eccentric contraction Equilibrium, 19 Delayed-onset muscle soreness high-velocity, in injury, 118 angular, 37–38, 37f of muscle, 116, 116f, 126, 127f conditions for, 41–42, 42f (DOMS), 136 dynamic, 20 Deltoid ligament, 442 Effusion, joint, 408–409 static, 19 Deltoid muscle, 238 Elastic cartilage, 80 Equinus, 495 Elastic component, of muscle, 122, 122f Erector spinae muscles, 180–181, 181f, function of, 263–264, 264f Elasticity, 87 in glenohumeral stabilization, 182f modulus of, 85–86 location and function of, 183 255–256, 255f Elastin, 76 overstretching of, 182 Dens (odontoid process), 157, 157f Elbow complex, 273–300 Eversion Dentition, and temporomandibular of ankle-foot complex, 438, 439f axis of motion of, 282–284, 282f–284f talar, 442 joint, 225 effects of age on, 296–297, 296t Exercise(s) Dermatan sulfate, 74, 74t effects of injury on, 297–299, effect of, on connective tissues, Desmin, 114 Diaphragmatic muscles, 201–204, 297f–299f 104–106 functional activities of, 295, 296f, for low back pain, 184–185, 185f 202f–204f isoinertial, and testing, 128–129 Diarthrodial (nonsynovial) joints, 296t isokinetic, and testing, 128 humeroradial joint in. See also plyometric, 128 93–98, 94f–98f weight-bearing vs. non–weight- Diarthroses, 93–98, 94f–98f Humeroradial joint. Digastric muscles, 222, 222f function of, 282–288 bearing Digital tendon sheath, 326 structure of, 274–282 in quadriceps strengthening, Digits(s). See Finger(s); Thumb; Toe(s). humeroulnar joint in. See also Disk(s). See also Meniscus. Humeroulnar joint. 418–419 function of, 282–288 with patellofemoral pain, 428–429, articular, of temporomandibular structure of, 274–282 joint, 217–218, 218f joint capsule of, 276–277, 278f 429f ligaments of, 278–280, 279f Exercise-induced injury, 136 displacement of, 227 mobility of, 295–296 Expiratory reserve volume, 201, 201t in mandibular elevation and muscles of, 280–282, 281f Extension, 9 action of, 286–288, 287f–288f depression, 220–221 effects of aging on, 296t patellar, 422 cartilaginous, 91 factors affecting activity of, 286 tibiofemoral, 409–412, 410f–412f intervertebral. See Intervertebral range of motion of, 284–286 two-joint muscle effects on, 285, range of motion of, 411 disk(s). role of cruciate ligaments and Displacement. See also Motion. 285f relationship of, to hand and wrist, menisci in, 410–411, 410f–411f direction of, 9 Extension moment, 487 in space, location of, 7–9, 7f–8f 295–296 Extensor(s) magnitude of, 9–10, 10f stability of, 295–296 rate of, 10, 10f–11f Elderly. See also Age (aging). elbow, 287–288, 288f types of, 6–7, 6f–7f gait in, 559–560 finger, 328–329, 328f–329f Distance variables, in gait, 522 postural alignment in, 509–510, 509t, Distraction forces, joint, 28–31, 28f, mechanism of action of, 329–333, 30f–31f 510f 330f Distraction injury, effects of, on elbow Electromyography, in muscle activity complex, 297–298, 298f hip, 376 Dorsal intercalated segmental instability monitoring, 482 knee, 415–419, 416f–419f (DISI), 314, 314f–315f Elongation, 83 vertebral column, 152–153, 152f Dorsiflexion wrist, 312–313, 312f of ankle-foot complex, 438, 439f, tensile load producing, 83 Extensor carpi radialis brevis muscle, Endochondral ossification, 81 281, 281f, 316 444–445 Endomysium, 121, 121f Extensor carpi radialis longus muscle, of head of talus, 449, 450f Endotendon, 78 281, 281f, 316 of rays, 459 Energy Extensor carpi ulnaris muscle, 281, Dorsiflexion moment, 488 281f Dorsoradial ligaments, 337 in running gait, 557f, 558 Extensor carpi ulnaris tendon, 307 Double-support time, in gait, 523 kinematic approach to, 536 Extensor digiti minimi muscle, 316 Dowager’s hump, 496, 497f mechanical Extensor digitorum brevis muscle, 473t Dynamic equilibrium, 20 Extensor digitorum communis muscle, Dynamic posture, 480–484, 480f. See also kinematic approach to, 534–536, 281, 281f, 316 Posture. 535f–536f Extensor digitorum longus muscle, 445 control in, 481 Extensor digitorum minimi muscle, of walking, 534 281, 281f Energy requirements, of gait, 534 Entactin, 74

Copyright © 2005 by F. A. Davis. Index ■ 573 Extensor hallucis longus muscle, 445 extensors of, 328–329, 328f–329f in sagittal plane postural deviations, Extensor hood, 322 mechanism of action of, 329–333, 493–494, 494f Extensor indicis proprius muscle, 316 330f Extensor pollicis brevis muscle, 317 kinematics and kinetics of, 534 Extensor pollicis longus muscle, flexors of, 325–328, 325f movement of, through space, 372, mechanisms of, 326–328, 327f 316–317, 318f 372f Extensor retinaculum, 317 interphalangeal joints of, 96, 96f, muscles of, 468–472, 469f–471f, 473t Extracellular matrix, 73–77 324–325, 324f plantar aponeurosis of, 466–467, 467f supinated (pes cavus), 472–473, 499, fibrillar component in, 74–77, 76f, metacarpophalangeal joints of, 76t 321–325 500f weight distribution of, 467–468, 467f interfibrillar component in, 73–74, musculature of Foramen of Weitbrecht, 248 73t, 74t, 75f, 75t extensor mechanism in, 329–333, Force(s), 10–19 330f action-reaction, 24, 25 Extremities, upper, and gait, kinematics extrinsic extensors, 328–329, 328f analysis of, multisegment (closed- and kinetics of, 553 extrinsic flexors, 325–328, 325f interossei, 333–335, 334f, 336t chain), 63–66, 64f–65f F intrinsic, 333–336 angle of application of, moment arm lumbrical, 335–336, 335f Failure load, 83 and, 46–48, 47f–48f Fascia trigger, 328 calculation of, 11 Finger flexor grasp, 326, 326f components of, 53–60 muscle, 121 Finger tricks, 322–323, 332f plantar, 461, 466–467, 466f Flat foot (pes planus), 449, 457–458, and angle of application, 58–60, thoracolumbar, 169–170, 170f 58f–59f Fascia lata, 402 498–499, 499f–500f Fascicles, 114, 114f archy, 472 determination of magnitude of, muscle, 120, 120f in gait cycle, 520, 521f 55–58, 56f–57f Fasciitis, plantar, 467 Flexion, 9 Fat pad, infrapatellar (Hoffa’s), 409 of metatarsophalangeal joints, perpendicular and parallel, 54–60, Femur 55f anatomic (longitudinal) axis of, 462–463, 463f patellar, 422 rotatory effects of, 61–62, 61f–62f 395–396 tibiofemoral, 409–412, 410f–412f translatory effects of, 60–62, angle of inclination of, 358, range of motion of, 411 60f–62f 359f–360f role of cruciate ligaments and composition of, 16 angle of torsion of, 358–361, compression, 30–31, 31f menisci in, 410–411, 410f–411f connective tissue, 83–84, 84f–85f 360f–361f Flexion moment, 36, 487 contact, 24–25, 25f angulation of, 357–361 Flexion relaxation (FR) phenomenon, definition of, 10–12 bony abnormalities in, 387–388 distraction, 21, 29–30, 30f head of 181, 504 external, 11 Flexor(s) friction, 32–35, 32f–33f blood supply to, 363 gravitational, 15–19, 15f–19f, 485. See ligament of, 362, 363f elbow, 286–287, 287f–288f in tibiofemoral joint, 394–395, finger, 325–328, 325f also Gravity. 394f–395f ground reaction, 485, 485f motion of, on acetabulum, 366–367, mechanisms of, 326–328, 327f inertial, 485 367f hip, 374–375 internal, 12 motion of pelvis on, 368–371, knee, 414–415, 414f–415f internal/external, in gait, 530, 369f–371f vertebral column, 151–152, 152f neck of, stresses in, 366 531f–532f, 531f–533f, 532, 533f, stabilization of, 29–30, 30f lateral, 153, 153f 534 stress and strain in, 84, 86f wrist, 312–313, 312f muscle, 42–44, 42f–44f Fibrillar component, of extracellular Flexor carpi radialis muscle, 280, 281f, naming of, 14 matrix, 74–77, 76f, 76t 316, 317f normal, 25 Fibroblasts, 72, 72t, 82 Flexor carpi ulnaris muscle, 280, 281f primary rule of, 12 Fibrocartilage, 80, 92 Flexor carpi ulnaris tendon, 307 reaction, 30–31, 31f triangular. See Triangular fibrocarti- Flexor digiti minimi muscle, 473t tensile forces and, 26–28, 27f lage complex. Flexor digitorum longus muscle, 445 resultant, 16 Fibrocartilaginous enthesis, 79 Flexor digitorum profundus muscle, shear, 32–35, 32f–33f Fibrocytes, 72, 82 316, 317f SI unit of, 13. See also Newton (N). Fibronectin, 74 Flexor digitorum superficialis muscle, tensile, 26–28, 26f–27f Fibrosis, capsular, of temporomandibu- 280, 281f, 316, 317f units of, 11–12 lar joint, 226 Flexor hallucis brevis muscle, 473t Force couple, 36 Fibrous enthesis, 79 Flexor hallucis longus muscle, 445 Force system Fibrous joints, 91–92, 91f–92f Flexor pollicis longus muscle, 316, 317f concurrent, 22–24, 22f–24f Fibrous layer, of knee joint capsule, Fluid-film lubrication, of joints, 95 linear, 20f, 21, 22f 401–402, 402f Foot additional considerations in, 25–35 Fibular facet, of talus, 441 arches of, 464–468 horizontal, 32, 34–35 Finger(s) vertical, 32, 34–35 carpometacarpal joints of, 319–321, function of, 465–468 parallel, 38–41, 38f–41f 319f muscular contribution to, 468 Force vectors, 12–15, 13f–14f structure of, 464–465, 465f characteristics of, 14 bones of, 438, 438f ground reaction, 485, 486, 486f cavus, 449 muscle, 42–44, 42f–44f flat. See Flat foot (pes planus). Force-velocity curve, 125f, 126 in frontal plane postural deviations, 498–500, 499f–500f

Copyright © 2005 by F. A. Davis. 574 ■ Index Force-velocity relationship, in muscle, kinematics of, 519–527 Gluteus minimus muscle, 376 125–126, 125f kinetics of, 527–551 Glycoproteins, 73, 74, 75t mechanical power and work in, 537, Glycosaminoglycans, 73–74, 74t Forearm Golgi tendon organ, 133 functional activities of, 296t 538f–540f, 541t, 542–543, 542t Gomphosis joint, 91–92 long axis of, 283–284, 284f muscle activity in, 543–544, Gracilis muscle, 367, 375, 409, 414f, 415 Grasp, finger flexor, 326, 326f Forefoot, 438, 438f. See also Foot. 544f–546f, 546–547 Grasping, 483 Forefoot valgus, 473 overview of, 517–518 Grasshopper-eyes patella, 500, 501f Forefoot varus, 460, 460f pathologic, 382 Gravitational force, 485 Forward head posture, 497, 497t pelvic rotation in, 371, 371f Gravitational moments, opposition to, Fossa running, 555–558, 555f–557f, 558t sagittal plane analysis of, 547, in standing posture, 488–489, 489f acetabular, 357 Gravity, 528 coronoid, 274, 274f 548f–552f, 551 glenoid, 216, 216f sagittal plane joint angles in, 524, center of. See Center of gravity olecranon, 274, 274f (CoG). radial, 274, 274f 525f–526f, 527 Fovea, 275, 358 stair, 553–555, 553f, 553t, 554t forces of, 15–19, 15f–19f Fovea capitis, 357, 357f terminology of, 522–524, 523f composition of, 15–16, 15f Fracture, 87 time/distance variables of, normative external, 11 of distal radius, 308, 309f of hip, 386–387 values for, 522, 522t line of. See Line of gravity (LoG). of tibial plateau, 430 transverse plane joint angles in, 527 segmental centers of, 15–16, 15f Free speed, of gait, 523 trunk and, kinematics and kinetics of, Grind test, positive, 338 Friction Grip kinetic, 34 551–553, 552f cylindrical, 341–343, 342f static, 33–34, 33f upper extremities and, kinematics hook, 343–344, 343f tendon, 60–61, 61f power, 341–344 Friction force, 32–35, 32f–33f and kinetics of, 553 spherical, 343, 343f Frontal plane, of body, 8, 8f walking Ground reaction forces, 485, 485f alignment and analysis of, 498, 498f, of gait, 527–528 mechanical energy of, 534 498t, 499t tasks for, 518 sagittal plane analysis in, 547, deviations from optimal alignment Gait cycle, phase(s) of, 519–522 548f–552f, 551 stance, 519f–522f, 520 in, 498–503 subphases of, 521 Ground substance, 73 Frontal plane joint angles, in gait, 526f, swing, 519f–522f, 522 Gastrocnemius muscle, 400, 414, 445 H 527 shortening of, 470 Frontal plane moments, in gait, 532, Gemellus inferior muscle, 377 H zone, 115, 115f Gemellus superior muscle, 377 Hallux rigidus, 462 533f Gender, effect of, on gait, 560–561 Hallux valgus, 462, 463, 463f Functional impairment, in abnormal General motion, 6–7 Hamate, 306f, 307 Genu recurvatum, 411, 495, 495f Hammer toes, 462, 463f, 494, 494f gait, 562–564 Genu valgum (knock knees), 396, 498, Hamstring muscles, 367, 414 Functional residual capacity, 201, 201t 500, 500f Hand complex, 319–346, 319f Fusiform (strap) muscle, 120 Genu varum (bow legs), 396, 500, 500f Gibbus (humpback deformity), 497, claw, 330, 330f G 497f fingers of. See Finger(s). Glenohumeral joint, 246–259, 246f functional position of, 346, 346f Gait, 517–564 articulating surfaces of, 246–247, power grip of, 341–344 abnormal, 561–564 247f–248f adaptation/compensation for, bursae of, 252 cylindrical, 341–343, 342f 563–564 capsule of, 248, 249f, 254 hook, 343–344, 343f functional impairment in, 562–564 dynamic stabilization of, 255–259 spherical, 343, 343f structural impairment in, 562 biceps brachii muscle in, 257, 257f prehension activities of, 340–346, analysis of, 528–530, 529f, 530t costs of, 258–259 center of pressure in, 528, 528f deltoid muscle in, 255–256, 255f 341f determinants of, 527 rotator cuff and, 256, 256f grip in, 340–344 effect of age on, 559–560 supraspinatus muscle in, 256–257 handling in, 344–346 effect of assisted devices on, 561 hypomobility of, 263 lateral, 344 effect of gender on, 560–561 impingement of, symptoms of, 252 pad-to-pad, 344, 345f effect of orthoses on, 561 ligaments of, 248–250, 249f–251f pad-to-side, 345–346, 345f energy requirements of, 534 motion of, 252–254, 253f–254f tip-to-tip, 344–345, 345f forces, moments, and conventions of, in shoulder complex, 259–260, relationship of elbow complex to, 530–534 295–296 frontal plane joint angles in, 527 259f–260f splinting of, in anti-deformity posi- general features of, 518–519, 518f static stabilization of, 254–255, 255f tion, 325, 325f ground reaction force of, 527–528 Glenoid fossa, 216, 216f thumb of, 337–340. See also Thumb. ground-level, vs. stair gait, 554–555 Glenoid labrum, 248, 249f Handling, precision, 344–346 initiation of, 518–519 Glenoid spine, posterior, 216, 216f Head avoidance of instability in, 519 Gluteus maximus gait, 563 in sagittal plane postural deviations, inverse dynamic approach to, 518 Gluteus maximus muscle, 180, 180f, 497, 497t joint motion in, 524, 525f–526f, 527 376, 415 in standing posture analysis, 492, Gluteus medius gait, 382, 562–563 492t Gluteus medius muscle, 376

Copyright © 2005 by F. A. Davis. Index ■ 575 movement of, through space, pathology of, 385–388 Immobilization 371–372, 371f structure of, 356–366 effects of weight-bearing of, structural adapta- deleterious, 103–104 Head stabilization in space (HSS), 484 in lengthened position, 135 Head stabilization on trunk (HST), tions to, 365–366, 365f–367f in shortened position, 135 Hip synergy, 482 of joints, 103–104, 104t 484 Hoffa’s (infrapatellar) fat pad, 409 Head-stabilizing strategies, 483–484 Hook grip, 343–344, 343f Impingement, of glenohumeral joint, Heel-off, in gait cycle, 520, 521f Hoop stresses, 90 252 Heel strike, in gait cycle, 520, 520f–521f Horns, of meniscus, 397 Helical axis of motion (HaM), 7 Housemaid’s knee, 430 Inertia, 19, 528 Heparin sulfate, 74, 74t Humeral ligaments, transverse, 257, Newton’s law of, 19–20, 31–32, 31f Hindfoot, 438, 438f. See also Foot. Hindfoot pronation, weight-bearing, 257f Inertial force, 485 Humeroradial joint Infantile scoliosis, 501 and transverse tarsal joint motion, Infants, postural control in, 509 455–456, 457f articulating surfaces of, 276, Inflammation, of temporomandibular Hindfoot supination, weight-bearing, 277f–278f and transverse tarsal joint, 456–467, joint, 226 457f axis of motion of, 282–284, 284f Infrapatellar (Hoffa’s) fat pad, 409 Hinge joint(s), 96 capsule of, 276–277, 278f Infraspinatus muscles, 256, 256f Hip joint, 355–388, 356f function of, 282–288 arthrosis in, 386 structure of, 274–282 function of, 264 articular congruence of, 361–362, Humeroulnar joint Initial swing, in gait cycle, 522 articulating surfaces of, 274, 274f Injury. See also under anatomy; specific 361f axis of motion of, 282–284, 284f articular surface of capsule of, 276–277, 278f injury. carrying angle of, 284, 284f compression, 297, 297f–298f distal, 358–361, 358f–361f closed-packed position of, 285 distraction, 297–298, 298f proximal, 356–358, 356f–357f function of, 282–288 effects of, 135–136 bony femoral abnormalities in, structure of, 274–282 387–388 Humerus, 234f on elbow complex, 297–299, capsule of, 362 articulating surfaces on, 274, 274f 297f–299f capsuloligamentous tension in, 364 long axis of, 283–284, 284f compression of Humpback deformity (gibbus), 497, on joints, 102–103 in bilateral stance, 379 497f high-velocity eccentric contraction in, in unilateral stance, 380 Hyaline cartilage, 80, 92 with cane contralaterally, 383–384 design of, 81 118 structure of, 80f prevention of, 185–186, 185f hypothesized calculation of, zones of, 80–81 384–385 Hyaluronan, 74, 74t squat lift vs. stoop lift in, 185–186, Hyaluronate, 95 185f with cane ipsilaterally, 383 Hydrodynamic lubrication, of joints, 95 with lateral lean, 382 Hydrostatic (weeping) lubrication, of to anterior cruciate ligament, 405, dysplastic, 388 joints, 95 406f articular contact in, 361–362, 362f Hyperextension stabilizers, range of motion of, 367–368, 368f anterior/posterior, of knee, to knee joint, 429–431 fracture of, 386–387 419t–420t to patellofemoral joint, 430–431 function of, 366–378 Hypermobility, 99 to tibiofemoral joint, 429–430 coordinated motions in, 371–373, of temporomandibular joint, 226–227 Innervation Hypertrophied synovial fold, 278 of intervertebral disks, 147 371f–373f, 374t Hypomobility, 99 of meniscus, 399 motion of femur on acetabulum in, of acromioclavicular joint, 263 Inputs/outputs, absent or altered, in of glenohumeral joint, 263 posture control, 481–482 366–367, 367f of sternoclavicular joint, 263 Inspiration, thoracoabdominal move- motion of pelvis on femur in, Hysteresis, 88f, 89 ment of, 202, 203f Inspiratory reserve volume, 201, 201t 368–371, 369f–371f I Instability gait affecting, 541t, 542t avoidance of, in initiation of gait, in standing posture analysis, 489, I (isotropic) band, 115, 115f Iliacus muscle, 184, 374 519 489f–490f Iliocostalis lumborum muscle, 180, 181f knee, posterolateral/posteromedial, ligaments of, 362–364, 363f–364f Iliofemoral ligament, 363, 363f musculature of, 373–378 Iliolumbar ligament, 151t, 169, 169f 420 Iliopsoas muscle, 374 Interbody joint(s) abductor, 376 Iliotibial band adductor, 375 of cervical region, 161, 161f bilateral stance and, 378–379 hip, 367 of lumbar region, 168 extensor, 376 knee, 402, 407–408, 408f of thoracic region, 165 flexor, 373–375 Iliotibial tract, 121, 122f Intercalated segment, of carpal row, lateral rotator, 377–378, 378f Ilium, articulating surfaces on, 173, 312 medial rotator, 378 173f Intercarpal ligaments, 319, 319f unilateral stance and, 379–381, dorsal, 311, 311f Interchondral joints, 198 380f Interclavicular ligaments, 234 reduction of muscle forces in, Intercondylar notch, 394 Intercondylar tubercles, 395, 395f 381–385 Intercostal membrane, 204 pain in, 377 Intercostal muscles, 203–204, 204f Intercuspation, maximal, 225 adjustment to carried load and, Interdiskal pressures 385 in lying posture, 508, 508f in sitting posture, 505–506, 505f–506f reduction of, strategies in, 385