Basic Biomechanics of the Musculoskeletal System-3rd Edition

ception is the observation that leg-crossing (upper thin people. But this may also hold for heavy peopi legs crossed or ankle on knee) may result in less ac- because with an increase of volume, the weight i tivity of the internal oblique abdominal muscles creases with the third power (m]) but the suppo that have the same orientation as the transverse ab~ surface only with the second power of length (m') dominal muscles (Fig. 17-11) (Snijders et al\" 1995). The most unconstrained form of the lumb By crossing the legs, an ahernativc and less fatigu- spine is found when the angle bet\\vcen the trun ing means is found for self-bracing of the Sl joints. and femur is 135\" (Keegan, 1953). Furthermore, th muscle running from the lumbar spine to the fem Lying (111. psoas major, part of the 111. iliopsoas) can shortened, which raises tension in this muscle an causes a hollow back in supine posture. This can A bed is a body support surface on which prolonged improved by exorotation of the legs and, if this is i \"'. and complete rest must be found. It is a combina- sufficient, by lying on the side. When lying 011 t tion of a mattress, a mattress carrier, and a bed side. the spine should not bend laterally. resemblin frame or bedstead. However. in many countries it is the scoliotic form. This occurs in persons with pr customary to sleep on a spread-out mat on the floor. nounced waists and little give of the mattress in t Three types of mattresses can be distinguished: polyethel; foam rubber, and internally sprung. There are several kinds of mallress carriers, like the wire-spiral mat, the hardboard boltom, lathes thar can tih, the box spring. and a carrier simply made of planks with distances of approximately 7 cm. Many combinations of mattress and mattress carrier arc possible, but not every combination is appropriate. A good bed should (1) adapt to body curvatures, (2) remain nal, (3) have a pleasant spring action, (4) have good ventilation, and (5) not be too warm or too cold, Aspects I to 3 concern body support that evenly spreads the pressure on protruding (bony) parts. gives a straight spine when lying on the side, and gives a natural S-shape to the spine in the supine posture. Lying on a horizontal surface is special because each body part receives separate support with minimal pressure on skin, and under- lying tissues and joints can be kepl in a relaxed po- sition. The result must be that for static equilib- rium, muscle action is superfluous. For separate support of the head, a pillow is needed. The thickness of the pillow is related to the curvature of the spine: the more curved (especially in older people), the thicker the pillow (Fig. 17-22). II' the pillow is too thin, the head must be tilted backward. A pillow that is too thick is inconvenient because it causes a bend in the cervical spine. This bend can also occur when the pillow is harel. Wilh the shape of a coconut resulting in a concentrated force on the head at the side of the crown. Pillows must be pliable to also support the neck. Pillows must be pliable to also support the neck. The thic A bed that is too hard results in restless change of ness of the pillow is related to the curvature of the spine posture to unload areas with disturbed blood flow. because hyperextension or a sharp bend of the cervical Normally. people change posture 20 times per night. spine should be avoided. One can imagine that large pressure occurs with

~----------- r Decubitus Skin Ulcerations I A 90-year-old man. v,nth a pelvIC fraClure and cognitive lim-I itatians. In his second week ai hospiializatlon. the patient ! be~.is spending 10.0% of h.is t1rl1e In. Prolonged pressure and Ii shear stresses In the skin hnearly aheet the oxygen saturation of the tissue and thus the nutrrtlon of it. In aSSOCiation with ! the natural aging of the collagen tissue and the slc\\-ver metae-II olism associated with advanced age, the inactivity increases , the likelihood of developing a decubitus ulcer. I Sitting in bed results in shear on the coccyx (here. approxi- mately 100 N). This is analogous to the horizontal seat of I Figure 17-14, DECUBITUS • It is assumed that prolonged pressure (without region of the shoulder and the hip. Therefore, the shear) of 35 to 40111111 Hg (4.6-5.3 kPa) can be tol- criterion of conformity has been illlroduced. This is erated. Shear dccr~ases lhc LOlerablc pressure con- the sinking of two square plates of 20 x 20 cm at a sidcrabl:' (Fig. 17-24). Ox:'gen saturation was mca- distance of 60 em, each loaded with 20 kg (a shOld- slIl'ed withoLlt (upper cUl\"Ve) and with (lower del' and a hip), measured in relation to a point on cUl\\,e) a shear stress of 3.1 kPa (Goossens, Zegers. the mattress in the middle between the plates. The 1-loek nlll Dijke, & Snijders, 1994). This diagram greater the depth to which the plates sink, the shows a dramatic decrease of saturation in the greater the conformity. In a comparative study, a case of additional shear force. Therefore, silling in level difference of more than 3.5 em was judged as bed is a pro\\\"ocation of decubilus skin ulcerations, good, a difference of 2.5 to 3.5 em as reasonable, which can be soh-cd b~1 tilting the mattress in ac- and of less than 2.5 em as moderate (Het Bed, 1979). - - No shear - - Shear 3.1 KPa SITTING IN BED 15 Sitting in bed is common, especially in hospitals in \"\"~- 12 which the head portion can be raised upwal'd. \\Vith a horizontal mattress, the same biomechanical c model holds as in Figure 17-14. Sitting in bed on a horizontal mattress (Fig, 17-23) gives rise to shear 0 forces (in the order of magnitude of 100 N) on the skin and underlying tissues of the bottom. As a con- 9.~ sequence, the pelvis moves little by little on the mat- tress, the night dress creeps upward. and the under- c wear pulls tight in the crotch (Snijders, 1988). Taller people have the advantage that they can come to a >'\"- stop with the feet against the board at the foot end. '\"c 6 Figure 17-23 shows that lumbar support is absent, which causes lumbar kyphosis and the pelvis to rest 0> on the as COCC)'X instead of on the ischial tuberosi- ties. The combination of pressure and shear is a •~ provocation of decubitus skin ulcerations (Case Study 17-2). 03 c '\"(J) 0 o 3 69 12 15 Pressure [KPa] Oxygen saturation in subcutaneous tissue under pressure (upper curve) decreases dramatically by adding 3,1 kPa shear stress (lower curve). Reprinted ~'1ith permission from Goossens. R.H.M.. Zegers. R., Hoek van Dlj\"J:e, G.A., ef ell. (994). !nfftl€!fJce of shear on skin oxygen rension, J (lin Physlol, 14, 711-7/8,

Solid material B A Fluid Gas c o A. Equilibrium of a body on a mattress of solid material. Re- mattress with a loose cover; less shear than in B. D. Equili rium of the body on gas. A favorable, uniform pressure d a,stricted support surface. Fluid mattress with an elastic en- bution over almost the maximal available supporting surf velope. The highest pressure is at the deepest point. C, Fluid cor-dance with Figure 17-14C. This folding princi- largest bod).' surface is involved in support w ple is now applied in hospital beds and in beds for the body sinks deep in the maltress (Holsche home care. aI., 1994). The medium for antidecubitus mattresses can Swnmarv be divided in four groups: solid material. fluid, gas, and a combination of these media. Solid ma- Any deviation from the anatomical pos terials are foam, sheepskin. woolen blankets, etc. generates increased tension in soft tissue and Deep impression of the material results in a larger creased loading on the skeletal structures. force (Fig. 17-25A). The ideal material should have a horizontal (isotonic) and adjustable spring The design of hurnal{ tools should inc characteristic. For fluid, a good envelope is knowledge of biomechanics and its effect on needed (Fig. 17-25B). Tensile forces in this enve- mans. lope contribute to bodS' support, but raise shear stresses. The supported surface is large but still Use and adaptation of supports, including the largest stresses are at the deepest point. Gas al- rests, back rests, and adjustable desks or beds, lows for the application of equal pressure along a help to decrease the load on musculoskeletal st large surface (Fig. t 7-25D). Chambers are neces- tures. sar.y to follow the contour of the body. Combina- tions of the foregoing are the \"air-fluidized\" beds, The most important factor to reducing loa hammocks, etc. For home situations, gas support the lumbar spine during lifting is to keep the is preferred, with an adjustable spring characteris- close to the body. For engineering purposes, the tic to accommodate bod)' weight. In all cases, the is to reduce the lever arm of the object.

REfERENCES Snijdc.:rs, C.J. (1991). Biolllc..:hani(,·s of fool gcnr. hallux \\·.I!gllS .1lH.I splay fool. In ,\\tH. J.dlSS (Ed), TIlt, FoOl (jIul ifS 0;'::0,._ Goossens. R.I·Uvl. & Snijdc:rs. C.l. (1995). Dc:si!!.11 ,ritcri~l for lIt.'rs (2nd cd.). rhil.lddphia: W.B. S'llllldcrs. the reduction of ShClll\" forces in beds and S~~ltS. J 8i0I1I,\" Snijdcrs: CJ., :\\?hi~n. J.c.r.M., Rid. ~\"'ll.J.i\\l.. d al. (1990). dWl1ics. 28(2).225-230. Rcadlllg and IIldlned surf.lc..-s. L.al/al, 335(8692}, 802. Goossens. R.H.M .. Zegers. R.• Hoek \\'an Dijkc. G.A .. ct ~II. Snij~lers. C.l .• .Hoek V;Jll Dijkc, G.A., 6: Roosch. E.R. (1991).:\\ (1994). Influellce of shear on skin oxygen !ellsion. J eJin ~101llt'~hanlcal model for the an.\\lysis of Ihl.' cen'ica! spine Ph)':;i\"/, 14, 111-118. III stauc postures. J Biol1w..)ulIl;c:.... 2-1(9),783-792. Hel Bcd. IIlSfi1l1l1l 1'oor fllfisllo/l{ltecJlllisdl Advic:s (lVI1A) \\'(111 Snijde!'s, c.J., Slagter. A.H.E .. Strik. R.. ct at. (1995). Wh\\' Ie!!· dc Nctlahllulsc \\'crclligillj; vall I-/lIiS\\'rDI/II't!II. Tl!stn:pol'/ (in crossing? The influl.'llcc of common postures on abdomi- Dutch). Gr:l\\'cnhagc: 1979. nal muscle acth·ity. Spilll.'. 20( IS}, 1989-1993. Holscher. T.G .. Goossens. R.IL\"!., Snijdr.:rs, C.l., c:1 al. (1994). Snijdl:r~, C,J. & Verduin, ~'1. (1973). Stabilograph. all <lCCU· A new low·cost anti·decubitus mattress for home care: Re- r~tl: Instrument for sciences inlcrrslcd in postural equilib- qllirctlWrHS and development. J RehaIJ Sci, 7(2).53-58. rium . ..tgressologie. l-1C, 1520. Snijdc-rs, c.J .. Vleeming. A., &. StOl.'Ck;II't, R. (1993). Trnnsfer h.nda. V (1980) . .\\1l1skel{llJlkliollsdiagJloslik. Verlag {iiI' .\\It:tJj· :';1/ Dr. EU'ald Fischer. LClI\\'cn. tAhceeD11VImabla~rgc; uHrHei.'den:lblactrcg~1. of IUlllbosacr.1i IOi:ld to iliac bones and h:gs. P;lrl I: Biome- Kecgnn, J. (1953). Aher'lIions of 10 d.l~llics of sdf.bracing of Ihe s'lcroiliac joints and its sig- posture .md seating. J BOlle )0;111 SIl,.~elY. 35. 589-603. SIlIflCanCe for treatmenl and c.xcrcise. Clill Biol1lc.'clulII;cs Moll v.m Chan:mte. A.W.• Snijdcrs. CJ .. & Mulder, P.C.H. 285-294. .. (1991). Posture control and Ihe risk of industrial .lCcidcnt: Wall, !\\.t., d.e Rid, \\t.P.J.M., van ,\\ghin.l, J.c.rJ\\'I., l'l al. (1992). Impwnng the sil!ing posture of Cr\\D/C,\\~<t workers bv in· A st.lbilographic invcstig'llion in u nU\\'al shipy'll·d. Ami 0(.'- ttlP l1y:;;<:IIe, 35(5),505-515. creasing VDU monitor working hcighl. Ergo/lomics, 35'(.4) Snijdcrs, C,J. (1988). Biomcchanical analysis of s~illcd pos· 427-436. .. for ortun:. IC..tART 88: hlfl.'l'/wtirmal COI1/'cn.'~,(.'l.' of lite Associ/I- liOI/ Ilti.' /\\d\\'allct:IlIClIl RelUlbilitafioll Tt:f.:llIlIllo\"\" i\\'lontrcal. 472-473. e>.' i.\",,\" I;:: I '0-

Biomechanics o Gai Ann E. Barr, Sherry I. Back Introduction Anatomical Considerations Hip Knee Ankle and Foot Upper Body Methods of Gait Analysis Gait Cycle Time-Distance Variables Angular Kinematics Hip Knee Ankle and Foot Talocrural Joint Subtalar Joint Midtarsal Joint Forefoot and Interphalangeal Joints Trunk and Pelvis Center of Mass Segmental Kinetics Joint Moments Hip Knee Ankle Joint Power Hip Knee Ankle Work and Energy Transfer Muscular Control Hip Knee Ankle and Foot Taloc(ural Joint Subtalar Joint Midtarsal Joint Forefoot and Interphalangeal JOints Summary References

Introduction ANKLE AND FOOT Bipedal locomotion, or gait, is a functional task Ankle motion is restricted by the morphologica requiring complex interactions and coordination constraints of the talocr-ural joint, which permi among most of the major joints of the body, par- only plantarllexion (extension) and dorsillexio ticularlv of the lower extremitv. This fundamental (Ilexion), Although frequently modeled in ga task ha~ been the subject of st;,dy by scientists for analysis as a rigid segment. the foot is required t several centuries, both with respect to description act as both a semirigid structure (as a spring durin of typical body movements and of pathological weight transfer and a lever arm during push-of conditions and therapeutic intcl'\"ventions. Gait and a rigid structure that permits adequate stabilit analysis and training in one form or another is a to support body weight. staple of physical therapy and rehabilitation mcdw icine practice. As technological advances become The movements of the ankle, subtalar, tarsa both more sophisticated and affordable, detailed metalHrsal, and phalangeal joints contribute t biomechanical analyses of gait increasingly can be the smooth progression of the body's center o performed in a clinical setting. This means that mass through space. Thcl-e are constant acljus the biomechanics of gait need to be more broadly Illents in these joints in response to the charac understood b)' both clinicians and researchers. In teristics of the supporting terrain and to the ac the paragrapl~s that folio\\\\', the anatomical charac- tions of the muscles that cross them, whic teristics of the major joints of the lower limb and provides a smooth interaction between the bod trunk will be summarized and their behavior dur- and the wide variety of supporting surfaces en ing level walking in healthy adults will be de· countered when walking. The loss of normal mo scribed. More detailed anatomy of the relevant tion or muscular function at these joints has a d joints and tissues can be found in other chapters rect effect nOt only on the fOOl and ankle bUI als of this book. on the remainder or the joints of the lower ex tremity. Anatomical Considerations UPPER BODY HIP The pelvis and thorax may be considered sepa During gait, motion abollt the coxofernoral, or hip, rately or, as in many studies in the literature, as joint is~ triaxial: nexion-extension occurs about rigid unit comprised of the head, arms, and trun a mecliolateral axis; adduction-abduction occurs about an anteroposterior axis: and internal-external (pelvis + thorax), or HAT, segment, The uppe rOlation occurs about a longitudinal axis. Although flexion-extension movements are of the highest am- limbs and head have not received as much atten plilude, motions in the other two planes are sub- tion as the trunk and lower limbs in the literature stantial and consistent both within and between in· Studies that do exist indicate that shoulder mo clividuals. In addition, impairments in all three tions occur pl-imarily as flexion-extension an movement planes can cause problematic deviations internal·external rotation at the glenohumera of the typical gail pattern althe hip and olher joints. joints. Elbow flexion-extension and forcarm prona tion-supination oceUI: Cervical spine motion is pri marily in flexion-extension and rotation to stabiliz visual gaze or facilitate the vestibulo·ocular refle as the body is propelled through the cnvironn1cnl KNEE lVlethods of Gait Analysis In the case of the knee, three degrees of fTeedom of The information presented in this chapter is sum angular rotation are also possible during gait. The marized from the scientific and clinical literature primary motion is knee nexion-extension about a which various laboratory methods have been llse mediolateral axis. Knee internal-external rotation to measure gait charactcristics, including strid and adduction·abduction (varus-valgus) may also oc- analysis, angular kinematic anal~;sis, force plmc an cut: but with less consistency and amplitude among foot pressure analysis, and electromyograph healthy individuals owing to soh tissue and bony (EMG) analysis, In stride analysis, the temporal s constraints to these motions. 43

quence of stance and swing are quantified using ei- terns. and load bearing of the lower cxtremities and, as a result, is cfflcicnt in translating the bod)/s cen- ther simple tools, slich as a stopwatch and ink and ter of muss in the ovcrall direction 01\" locomotion. A full gait cycle is defin~d by the OCCllrrcnce 01\" a ~e~ paper, or electromechanical instruments. stich as quential stance phase and swing phase by one limb, or a stride (Figs. 18-1 and 18-2). The limits of a pressure~sensitive switches imbedded in shoe in- stride can be demarcated by the occurrence of a specific gait event (e.g., initial COlll<:lct) on one limb serts or applied to the bollom of the fool. Stride to the next occurrence of that same event on the ip- silateral limb. analysis data arc used to calculate basic time- Stancc phase occupies 60(7\"0 of the stride and con- distance variables, which will be described in detail. sists of two pel\"iods of double limb support (initial Angular kinematic analysis lIses c1ectrogoniome- and tcrmillal), wh~n the contralateral foot is in con- tact with the ground, and an intermediate period of t!)', accelerometry, and optoelectronic techniques. single limb support. when the contralateral limb is engaged in swing phase. Stance can be decomposed ElectrogoniOlllelers arc available in uniaxial and into six events or period~. Initial contact or heel contact is ddlncd as the instant the foot makes con- multiaxial configurations and are attached directly tact with the floor. Loading response is an interval to the body segments on either side of the joint or during which the sole of the foot comes into con- joints of interest for the direct measurement of an~ gular displacement. Accelerometers arc attached to the bod.v. s c cr ll1ents of interest for the direct mea- ~ surement of segmental acceleration from which seg- mental velocities and displacements arc then dc- rivcd. Optoelcctronic techniques involve the use of video cameras to capture images of an individual walking. Such systems llsually include the use 01' reference markers. which are attached to the sub- ject, to estimate.: the location of joint axes and to as~ sist in digitization. Such camera systems require Stride/cycle careful calibration to locate anatomical markers and are often permanently installed in a \"gait labo- LTO LHC LTO LHC ratory.\" Force plate and foot pressure analysis tech- ! IIL. swing niques involve the recording of information at the L. stance IL. swing foot~noOl' interface during the stance phase of gait. Force plates measure the resultant ground reaction I force beneath the foot and the location of its point \" ,<\",,·,'1' O,\".,i ., I of application in the plane of the supporting sur- A. stance R. swing R. stance 60'% face. Pressure plates or insoles measure the load I 40~G distribution beneath the foot during stance. Force and pressure plates are often combined with angu· RHC RTO RHC RTO lar kinematic methods for the calculation of kinetic variables, such as joint moments. Stride/cycle EI\\tIG is used to record muscle activation during walking. Both surface and intramuscular sensing techniques are used in gait analysis. EMG is typi· cally combined with stride or angular kincmatic Schematic diagram of the temporal sequence of the gait cycle or stride showing complete right (shaded bars) and analysis to provide information about phasic mus- left strides. HC, heel/initial contact; TO. toe off, R. right; L. cle activation pallerns. EMG helps to explain the left. The areas of overlap between HC and TO represent motor performance underlying the kinematic and periods of double limb support, which coincide with the occurrence of pre-swing on the trailing limb and loading kinetic characteristics of gait. response on the leading limb. In the case of the right stride, initial double limb support (lasting -10% of the Gait Cycle stride) occurs from RHC to LTO, and terminal double limb suppo~_~ (lasting -10% of the stride) occurs from LHC to Bipedal locomotion is a cyclic activity consisting 01\" RTO. Reprinted with permission itom Bart; A.E. (998). Gair two phases for each limb, stance and swing. Gait is analysis. III J. Spivak & J. Zuckerman (Eds.), Orthopaedics-A morc or less symmetrical with regard to angular Comprehensive Study Gllide. New York: McGr~w-Hil!. motions of the major joints. muscle activation pat-

Fool Midslance Terminal Pre-swing Midswing stance lIat RTO RHC Terminal swing lnilial swing LHC Schematic diagram of the spatial sequence of the gait cycle Swing phase is demarcated by two events, TO and He, and or stride showing stance phase on the right and swing phase broken into three periods, initial swing (from -60 to 70% of on the left. He, heel/initial contact; TO, toe off, R, right; L, the stride), mid-swing (from -70 to 85% of the stride), and left. Stance phase is demarcated by two events, HC and TO. terminal swing (from ... 85 to 100% of the stride). Reprinted and broken into four periods, loading response (foot flat) with permission from Barr, A.E. (1998). Gait analysis. In I Spivak & (from -0 to 10% of the stride), midstance (from -10 to 30% I Zuckerman (Eds.), Orthopaedics-A Comprehensive Study Guide. of the stride), terminal stance (from -30 to 50%, of the New York: McGraw-Hili. stride), and pre-swing (from -50 to 60 % of the stride). tact with the noor and the weight of the body is ac- stride. During pre·swing, weight is transferred onto cepted onto the supporting limb. The loading re- the contralateral limb in preparation for swing sponse period coincides with the end of initial dou- phase. The end of pre-swing corresponds to toe off ble limb support at approximately 10 to 12% of the at which moment the foot breaks contact with the stride. Ivlidstancc is the period during which the floor, thereby demarcating 'the beginning of swing tibia rotates over the stationary fOOL in the direc- phase. tion of locomotion. The beginning of midstance co- incides with single limb SuppOrl and lasts from ap- Swing phase occupies 40% of the gait cycle and proximately 10 to 30% of the stride. Terminal is decomposed into three periods. Initial swing stance is the period during which the weight of the lasts From approximately 60 to 73% of the stride body is transferred fTom the hind and midfoot re- (approximately one third of swing phase), from toe gions onto the forefoot. It occurs from 30 to 50% of off until the swinging foot is opposite the stance the stride and coincides with the beginning of ter~ [001. Mid-swing ends when the tibia of the swing- minal double limb support. Pre·swing occurs si- ing limb is vertically oriented and lasts from 73 to multaneously with terminal double limb support 87% of the stride. Terminal swing lasts from 87 to and lasts from approximately 50 to 60% of the 100% of the stride and ends at the moment of ini- tial contact.

~ Normal Values ,. Time-Distance Variables for Time-Distance Parameters of Adult Gait at Free Walking Velocity Time-distance variables arc derived from the tem- poral and spatial occurrence of the stance and Stride or cycle time 1.0 to 1.2 mlsect Stride or cycle length swing phases. Normal values or these quantities are Step length 1.2 to 1.9 mil Step width provided in Table 18·1. Cadence 0.56 to 1.1 m-''' . Stride time refers to the time it takes to perform Velocity 7.7 to 9.6 em\" '. a single stride. Stride length refers to the distance 90 to 140 steps!~jnuteo.. covered b.y a stride in the direction of locomolion. Step is defined as the occurrence of an event on one 0.9 to 1.8 m/sec:.> root until the ncxt occurrence or thai same evenl on the opposite fool. It is most commonly delineated Reprinred with permission (rom Barr. A.E. (1998). Gait analysis. In 1. by sequential contralateral initial contact. Laterality Spivak & 1. Zuckerman. (eds.), Orthopedics: A Comprehensive Study is determined by the swinging limb; fOl' example, Guide. New York: McGraw·Hill, right step is delineated by left initial contact to the subsequent right initial contact. Step length refers ~Vafues adapted from multiple sources as summariled in Craik, R.t fit -\"S to the distance covered by a step in the direction of locomotion. Step width refers to the distance cov- Caris, CA. (1995). Gait Analysis: Theory dnd Application. Sr. Louis: -:~-­ ered by a step perpendicular to the direction or lo- comotion as measured from the points of contact on Mosby. l\"Values adapred from Whirr/e. M.W (1991). Gait Analysis: An lntro- duC!ion. Oxford: Builen'lorth·Heitlemann 20 40 40 10 30 30 0; 20 ~ 0 10 20 E \\\\ L::::JO~· ~ -10 10 '.\\ -10 ::::=:-.., c '\".'C0., -20 \\\\ -20 0 20 40 60 80 100 0 ::::::::::........~ -30 \".:'-.\\ -10 -40 .'., -20 0 0 20 40 60 80 100 ' .... 20 40 60 80 100 1.2 1.2 12 0.9 0; 0.9 0.6 1. 0.3 0.9 '\";E;. 0.6 0 0.6 C -0.3 ~ 0.3 -0.6 0.3 E 0 0 ....::::::._.:.. :2 0 B \".'c0., :\"/ \",/ 0 -0.3 ,..-' -0.3 -0.6 100 20 40 60 80 100 -0.6 100 0 20 40 60 80 0 20 40 60 80 Gail Cycle (%) A Gail Cycle (%) C Gail Cycle (%) Angular displacements and moments of the hip dur~ng level A (bottom). Hip extensor «0) and flexor (.>0) moment; walking at freely chosen velocity among normal subjects (25 B (top), Hip abduction «0) and adduction (>0) position; males, 4 females; 15 to 35 years of age). Solid Jines indicate B (bottom), Hip adductor «0) and abductor (>0) moment; mean values (ordinate) over the course of a single stride (ab- ( (top). Hip external rotation «0) and internal rotation (>0) scissa). qashed Jines indicate 90% bootstrap confidence inter- position; C (bottom), Hip internal rotator «0) and external vals. A (top), Hip flexion «0) and extension (>0) position; rotator (>0) moment.

the heels. Two sequential steps comprise a stride. Al- Bootstrap Method for the Statistical .. though step variables may differ fTom right to left Calculation of Confidence Intervals within an individual, stride variables will remain constant regardless of whether stride is delineated The boo ISHap method for the calculation of confidenc;.e,../:'\":,, -, '.; by right or left initial contacts, because stride con- intervals is an iterative technique whereby a population of \" sists of the SlIlllS of right and left steps. gait data time history curves (e.g., joint angular disp,la.c~~;':,,:>,\" Cadence is a measure of step frequency that is de~ ment or joint moment with respect to percent of the. g~it:::; fined as the nUI11ber of steps taken per unit time and is usually expressed in steps per minute. Velocity is cycle) is sampled with replacement. This sampling is ,;',,:, '\" defined as the distance covered in the direction of locomotion per unit time and is usually expressed in known as a bootstrap iteration. meters per second. Each curve in the population of interest is first ana-;: . Angular Kinematics Iyzed using a Fourier series representation, and a mean . '., This discussion will focus on joint angular displace- curve for the entire population is constructed by averag~ ments about the motion axes of the major lower limb and axial segments during level walking. Fig- iog [he Fourier coefficients. Then. for each bootstrap iter- ures 18-3 through 18-7 show examples of angular displacements at these motion segments over the ation. a sample of curves, equal in number to the popula- course of the stride in a healthy adult population (Calculation Box \\8-1). tion of curves from which the sample is taken, is HIP randomly selected with replacement and a mUltiplier is ,. calculated for that iteration. b. using the following for- At initial contact, the hip is flexed approximately 30' (Fig. 18-3A, top). Throughout terminal stance mula: phase, the hip extends until it reaches approxi- mately IDa of extension. During pre-swing and where f\\t),)! is the mean of all curves at point tj of. throughout the majority of swing phase, the hip nexes to approximately 35°, and then begins to ex· gait CYCle, F(tJ)tF. is the (T(t)b~mean of the bootstrap ;t;h;;e:';;:;~~~;d tend just prior to the next initial contact as the the same point of the gait cycle, and is lower limb is extended for placement of the foot on the ground. deviation of the bootstrap sample at the same poi!)t of The hip is neutral with respect to adduction- the gait cycle (Lenhoff. et aI., t996; and personal c·,·,mrnu- abduction at initial contact (Fig. 18-38, lOp). By the nication). end of initial double limb support 0'· early mid- Alier the final bootstrap iteration, the multipliers:\": stance, the hip achieves its maximum adduction po- sition of approximately 5°. Throughout the remain- M!bJ. are sorted by magnitUde and an M value is selected der of stance, the hip abducts to approximately 10' at toe off, then steadily adducts throughout swing in corresponding to the desired confidence limit at each preparation for the next initial contact. point in time. For example, if a 90% confidence interval is Hip rotational motions are more variable across individuals during gait (Fig. 18-3C, top). At initial desired, the value for M is selected such that it is larger contact, the hip is externally rotated approximately 5° and remains so throughout loading response and than 90% of [he remaining M values at a given pOint in early midstance. It begins to internally rotate to within 20 of neutral rotation by the middle of termi- the gait cycle. The standard deviation of [he population nal stance, then reverses direction and externally ro- tates, as the heel begins to rise, to its peak of 150 of mean is then multiplied by the appropriate M value at external rotation during initial swing. As the limb swings past the opposite stance leg during mid- each point in time of the gait cycle to obtain the confi- dence interval envelope. The stability of the confidence intervals obtained by the bootstrap method increases as .the population size creases and as the number of bootstrap iterations in- creases. The curves depicted in Figures 18·3 through were analyzed using the bootstrap method. For more spe- cific computational details. see Lenhoff et al. (1996). swing, i(s hip internally rotates to within 3° of neu- tral. then it oscillates between 3 and 5' or external rotation dudng terminal swing. Except for perhaps a brief period during the middle of (erminal swing, the hip never achieves an internally rotated position during gait. ;,~::-: . !I'l?~!l_!lIf'l!!j_!l_' w\" \"_,. \" \"=.__ _~\",m=,.\", ., ,Yo~',\"~\"_\",\", ?\".\" \",\"·':! !L\" \"-~, -_~,\".,_.-_c_>\" \" ' ~' ' . ., _,......,...-.. \"_,~ ._...\"'_: \", .:g, ,~o.~ .,---...,..,.\"...,.....,...\".,,,.\",.\":,-\",..·, : ,<\" -_g' f!b:>n_jz,ri1dG\", - '@,~'t 1.' FS0;._~ F' \"' ,;>_\".1§·.:~[.0..~; ,~\"} ':; ._<;- __

70,---------, 60 50,---------- 60 150 40 50 40 40 30 30 30 20 :--.. 20 20 10 /,'\"\"\"-', 10 o.~-=;---=--.=---=?--=-;-;-;;-~·.·dB·;0;';~:::§::-~-- 10,: ....:::- __ ). .--1o0· -,..l-..,---------~---~-~-, ...~. -..._. -10 o-l-~---''-''r--_-.--'k:i1 -20-'-------------' -20 \"', -10-'-----------\" o 20 40 60 80 100 --30 20 40 60 80 0 o 20 40 60 80 100 0.8 0.8 0.8,---------- 0.6 0.6 c; 0.6 0.4 0.4 0.2 0.2 ~ 0 O. .:~ E -0.2 i V-0.2 '-' -0.4 i'S 0.4 --0.4 - ' - - - - - - - - - - - - \" 0 C B o 20 40 60 80 ~ 0.2 c Gait Cycle (%) E a :2 0 c .'.0., -0.2 -0.4 20 40 60 80 100 20 40 60 80 100 0 Gait Cycle (~~) Gait Cycle (Q(o) A Angular displacements and moments of the knee during (>0) position; A (bottom), Flexor «0) and extensor (>0) level walking at freely chosen velocity among normal sub- ment; 8 (top). Knee abduction «O) and adduction (>0) jects (25 males. tI females; 15 to 35 years of age). Solid lines tion; B (bottom), Knee adductor «0) and abductor (>0) indicate mean values (ordinate) over the course of a single ment; C (top), Knee external rotation «0) and internal stride (abscissa). Dashed lines indicate 90% bootstrap confi- rotation (>0) position; C (bottom), Knee internal rotator dence intervals. A (top), Knee extension «0) and flexion and external rotator (>0) moment. KNEE in the relatively extended knee position. fndivi At initial contact. the knee is almost fully extended, skeletal alignment plays a major role in adduct then it gradually flexes toilS support phase peak flexion of approximately 20° during the early por- abduction movements at qlC knee. [n the nor tion of midstance (Fig. 18-4;1, top). During the laller portion of midstance. it again extends almost fully, sample presented in Figure 18-413 (top), whic and then nexes to approximately 40° during pre- predominantly males (25 males/29 subjccts), swing. Immediately following toe ofr, the knee con- knee remains in a slightly adduclCd (varus) posi tinues to ficx to its peak fiexion of 60 to 700 at mid- throughout stance but nucluates only within 2 swing, then extends again in preparation for the of neutral. Dudng pre-swing and initial swing next initial cOlllacl. weight is shifted onto the opposite limb. the k may aQ.~luct (move into valgus) as much as 10°, In the adduction-abduction plane of motion, the it then regains its adductec! position by term knee is quite stable during stance phase because 01\" swing. the presence of bony and ligamentous constraints Internal and external rotation about the during gait. as in the case of adduction-abduct is determined primarily by bony and ligamen

mechanisms and is variable across individuals. In In the normal sample of predominantly males addition, the placement of reference markers dur- (25 males/29 subjects) depicted in Figure 18-4C ing optoelectronic gait anal~/sis may introduce spe- (top), the knee is maintained in an externally ro~ cific offsets into angular calculations. For example, tated position throughollt stance and fluctuates be- in the data presented in Figure 18A, there was an tween 10 and 20°. Rotational motions about the external rotation offset as a result of placement of knee are strongly coupled with flexion-extension the ankle markers on the medial and lateral malle- motions. A comparison of Figure I8A, A-C (top) il- oli. Such technical differences may result in slight lustrates that during periods when the knee is flex- discrepancies bet\\vcen the absolute value of joint ing, it also internally rotates; whereas during peri- angular position at the knee as reported by differ- ods when the knee is extending, it also externally ent laboratories, although the relative displace- rotates. This coupling is related to the bony mor· ment range and overall patterns of motion should phology of the femoral condyles and tibial plateaus be simihll: as well as the displacements induced in this articu- lation by, especially, the anterior and posterior cru- ciate Iigalllents. 20 15· ANKLE AND FOOT 0; 10 Talocrural Joint :'s\" 5,-\\ At initial contact, the ankle joint is neutral or '\",0, a slightly plantarllexecl 3 to 5' (Fig. 18-5, top). From initial contact to loading response, the ankle planw «c -5 tarflexes (I.e., extends) to a maximulll of 7° as the foot is lowered to the supporting surface. Through- C 0 ···10 out midstance, the ankle dorsiflexes (i.e., flexes) to a maximum of t 5° as the lower leg rotates anteriorly -15 and medially over the supporting foot. During ter- minal stance and pre-swing, the ankle plantarflexes -20 to approximately 15° as body weight is transferred onto the contralateral limb. Immediately following a 20 40 60 80 100 toe off, the ankle rapidly dorsi flexes to the neutral position to attain toe clearance and then may plan- 0.5 tarflex slightly during terminal swing in preparation for initial contact. 0; O· Subtalar Joint ~ ;S -0.5 The subtalar joint rotates in, both stance and swing C (Fig. 18-6, bottom), but it is the motion during E'\" stance that influences the weight-bearing alignmen ·-1 \"\\ of the entire lower extremity. Like the ankle joint, the ::0:: arc of n10tion at the subtalar joint is small compared ,c '-::'\\'--' with the knee and the hip, but it is the motion pre- '-'-' sent at this joint that permits the foot to adapt to a '0 '1.5 varietY.Qf surfaces. The subtalar joint functions as a mitered hinge during gait to transmit internal and -2 20 40 60 80 100 external rotation from the tibia to rotations (ever- Gait Cycle (%) sion and inversion) about the foot. The subtalar join a also transmits inversion and eversion from the foo to external and internal rotation about the tibia. A Angular displacements and moments of the ankle during level walking at freely chosen velocity among normal sub· jects (25 males, 4 females; 15 to 35 years of age). Solid lines indicate mean values (ordinate) over the course of a single stride (abscissa). Dashed lines indicate 90% boot- strap confidence intervals. Top, ankle dorsiflexion (flexion) «0) and plantarflexion (extension) (>0) position; bottom, ankle plantarflexor (extensor) «0) and dorsiflexor (flexor) (>0) moment.

.. ..Toe off Midtarsal joint ..Heel contact Heel contact Motion about lite.: transverse a:\\is of the Inidt Ankle Stance phase j ; joint affects the longitudinal arch of the foot. rotation lowing forefoot contact during loading resp • Foot immobile Ii' the longitudinal arch n\"ttcns during single Sublalar support. The restoration of the arch occurs rolation heel rbe, o~_.._ - - o ' : - . 80 100 Midtarsal extension is another of the rn 20 40 60 nisms for shock absorption as body weight is ered Onto the stance limb during loading resp Percent of Walking Cycle and carly midstance. This motion, which acco nies forefoot contact at the onset of midstance Ankle and subtalar rotations during normal walking in a curs after subtalar eversion, single subject. Reprinted with permission from Wright, D.G., Desai, S.M., & Henderson, W.H. (1964). Action of the Finally, the interaction between the sub sub[alar and ankle-joint complex during the stance phase joint and the midtarsal joint is such that if of walking. J Bone JOInt SlJrg. 46A(2), 36/-382 tion at the subtalar joint is limited, then mo at the midtarsal joint will be limited. Simil when motion at the talonavicular joint is \\'cntcd, aimosl no motion is permitted at the talar joint. Joint Compensation: In- and Out-Toeing During loading response, the subtalar joint be- There is an important inteHelationship between the mo- tion at the ankle joint and the subialar joint during gait gins everting until peak eversion is reached by early that permits compensation between the joints. If this compensatory mechanism fails. there is increased stress in midstance (Fig. 18-6. bOllom). Peak eversion aver- these joints and possibly an Increased incidence of sec- ondary degenerative arthritis. For example. the degree of ages 4 to 60 This rapid eversion is followed b): grad- in-toeing (internal rotation at the ankle joint) and out- • toeing (external rotation at the ankle) affects the amount oj motion required at the subtalar joint. In the case of an ual inversion, with peak inversion achieved by pre- individual with excessive out-werng. the range of motion required at the ankle joint IS decreased, and at the sub- swing. The foot drifls back to neutral during swing t(llar joint, the mOlion required is increased. This occurs because the greatest motion will always occur about the followed by minimal inversion during the last 20% axis that is closest to perpendiC;Jlar to the plane of pro- gression. With out-toeing. the ankle joint axis is even Jess of the stride. perpendicular to the plane of progression than normal. The subtalar joint axis becomes oriented more perpendic Subtalar eversion is one of the mechanisms for ular to the plane of progression, and subsequently under goes a larger angular excursion. The reverse occurs with shock absorption as body weight is transferred increased in-toeing; the ankle joint axis becomes more perPe:ndicular to ttle plane of progression and the range onto the supporting foot during loading response of motion required at the ankle joint is increased. At the and early midstancc. Subtalar evcrsion is a normal sublalar joil1l. the mOlion reqUired is then decreased. On passive response to initial contact with the heel. of the compensations seen clinically for the loss of ankle range of motion is increased out-toeing, so that the mo- Because the body of the calcaneus is lateral to the tion required for walking can occur at the sub[alar joint. longitudinal axis of the tibia at initial contact, as load is applied to the talus, eversion occurs at the subtalar joint. Eversion of the subtalar joint un- locks the midtarsal joint to produce a relatively flexible forefoot. \\\\Then thc body's center of mass is translated more laterally as stance progresscs, the calcaneal support of the talus is decreased and the calcaneus invens. This is coupled with internal tibial rotation resulting from the shape of the ankle joint. Subtalar inversion helps to bring about stability of the fOOL during single limb stance (Box 18-1).

1;~1-- Forefoot and Interphalangeal Joints from the calcaneus to the metatarsal break imparts rigidity to the entire foot and facilitates push-off. I;1 c' AI initial contact, the LaCS are off the ground with the metatarsophalangeal joints in 25° of extension. A maximum of 58° of toe extension is reached ~14 The toes then Oex to neulral after for-croat contact at during pre-swing. During swing. the toes Oex the end of loading response. A ncutral position is slightl~1 but rernain in extcnsion. Finall~', there is a ! maintained throughollt midstance. Olll-jog terminal minimal increase in toe extension in preparation for stance, as the heel rises, the metatarsophalangeal initial contacl. Little or no flexion occurs at the ~~ joints (collectively known as the metatarsal break) metatarsophalangeal joint during walking, although extend to approxirnately 21 0 while the tocs remain some Illay be presenl during athlctic activities. ~;_-JI!i in contact with the ground and the hind fOOl lifts up into the air. This metatarsophalangeal extension Littie or no motion occurs al the interphalangeal places tension on the plantar aponeurosis, which in joints during gait wilh the exception that during turn exens a passive hind foot (calcaneal) inversion pre-swing, slight rlexion is occasionally noted. force. Tightening of the plantar aponeurosis also re· suits in supination of the foot and accentuation, or TRUNK AND PELVIS heightening, of the longitudinal arch of the fOOL The subsequent stirrening of the intcrtarsal joints At initial contact, the pelvis is tilted anteriorly ap- proximately 7° (Fig. 18-7A. bOLlom). rOlated for- 15 15 i 15 10 10 10 c; I -J '\".,'?\" 5 5 i 5· \" \"e;, 0?~/\"\"\"',~'1~ I .\",.- \" «c 0 0 -5 I --5 -10 0 20 40 60 80 100 -10 20 40 60 80 100 0 20 40 60 80 100 0 15 15 15 10 10 10 ',.... 5 \"c; 5 ........... 5 0 ? 0 ,- '--...' -5 -5 «e\"c;, 0 -10 -10 0 -5 0 C -10 20 40 60 80 100 B 20 40 60 80 100 to 40 60 80 100 0 Gait Cycle (Cl,{,) Gail Cycle (OiO) Gail Cycle (%) A Angular rotation of the trunk and pelvis during level walking Trunk downward « O) and upward (>O) tilt with respect to at freely chosen velocity among normal subjects (25 males, 4 females; 15 to 35 years of age). Solid lines indicate mean val- the stance limb; B (bottom), Pelvis downward «0) and up- ues (ordinate) over the course of a single stride, (abscissa). Dashed lines indicate 90% bootstrap confidence intervals. ward (>0) tilt with respect to the stance limb; C (top), Trunk A (top), Trunk posterior «0) and anterior (>0) lean; A (bot- tom), Pelvis posterior «0) and anterior (>0) tilt; B (top), backward « 0) and forward (>0) rotation with respect to the stance limb; C (bottom), Pelvis backwar.d «0) and for~ ward (>O) rotation with respect to the stance limb. , \"\",.,..

\\\\~ard approximately 5° (Fig. 18~7C. bOllom), and is trunk is rataled backward approximately 3° w level from right to left. During the loading re· the pelvis is rotated forward approximately 5° sponse, the pelvis tills upward on the stance limb anlpliludes of the angular displacemenls o side to a maximum of 5°, then it regains ncutrallilt trunk segment as rencctcd in the movement o at the nexl initial conlact of the swinging limb (Fig. shoulder girdle arc only slightly ullcnuated in 18·78, bOllom). During stance phase, the pelvis 1\"0· parison with the pelvic movements, as can be e tates backward on the stance limb side and tilts an· appreciated by comparing the lOP (trunk) La bo teriorly (hollom of Fig. 18-7 C & B, respectively). (pc)vis) plols in Figure 18-7. The total excursion for anteroposterior tilt is ap- proximately 5°; for lateral tilting, approximately CENTER OF MASS 10°; and for forward and backward rotation, ap· The body's center of mass remains located withi proximately 10°. pelvis anterior to the sacrum throughout the ga Tnmk motion during gait is opposite in direction. cle. It undergoes sinusoidal displacements in all planes with peak to peak excursions of approxim or out of phase, 10 the motions of Ihe pelvis (Fig. 18-7, A-C, lOp). For example, at initial conlaCl, the Flexion Hip Knee 40 Ankle ,-, ,' Joint j, ',, '~\" \\ rotation \" \"\"\",,,, , , , , Extension - 15 .- 15 ,.__..--.\" , ,Extensor 2.0 r· ,i Joint , moment I.-,',I - ... : ........ Flexor -1.0 t_~.~.. ~~_~~~:......~ ~ J L...__. ~ .•__.•; . _ .__' Generation 3~ \" ...,. --' ,- , , ,,,, ,,,, ~--~ , I' I JOin! ! l' '. \"',- ... ---- \" 1\\ power \"\" '' ~ 1- _ ~1 , _ - - ' - , ._--'----'--- - - '- - .L o 50 100 a 50 '\\ ,~ % Gait Cycle % Gait Cycle r \" - \"'\", # ...... Absorption -2 L __l __~~_ -L----' a 50 100 % Gait Cycle Joint power profiles in watts/kg of body weight (bottom ments in Nm/kg body weight. Joint motions are in degr row) of the hip (left column), knee (middle column), and an· Reprinredwilh permission from Gage. l.R. (1991). Gait Analy kle (right column) for flexion-extension motions (top row) Cerebral Palsy (p. 31). LOlldon: Mac Keith Press. during level walking. The middle row shows the joint mo·

3 em in the vertical direction, 4 em in the lateral di- Hip rection, and 2 em in the anteroposterior direction. At initial contact, there is an extensor moment Segnzental Kinetics about the hip that fluctuates at first, then stabilizes at approximately 5 Nm/kg (Fig. 18-3;1, bottom). In gait analysis, the human body is modeled as a This extensor moment persists through early mid- stance and then reverses to a flexor moment in the mechanical system of anatomical segments linked latter third of midstance. For the remainder of stance, there is a hip flexor moment that peaks at together by the joints. Kinetic computations in approximately 1 Nm/kg ncar the end of terminal stance. gait analvsis make use of angular kinematic and force dat~, ~ Although the hip moment about the anteroposte- rior axis is adductor at initial contact (Fig. 18-3B, JOINT MOMENTS bottom), it rapidly' reverses to an abductor moment of approximately 0.7 Nm/kg during loading re- A moment is defined as the vector cross-product of sponse. As the opposite limb s\\vings ncar the mid- a force vector and the perpendicular distance of line of the body during midslance, the stance limb the joint center from the line of action of that hip abductor moment decreases to approximately force vector. Moments arc frequently expressed in 0.4 Nm/kg, but it once again increases to 0.7 Nm/kg Nm pCI' kg of body \\veight in gait analysis (i.e., during terminal stance (Box 18-2). normalized to body weight). The effect of mo- ments is to cause a tendency for joint rotation. In ~'----'-------------------_._-'-_. this discussion, the term moment \\viII refer to the internal moment generated about the joint in ~ Gait Deviations question. A knee extensor moment, for example, refers to the internal moment of Force that tends I Loss of hip abductor strength or pain of the coxofemoral to rotate the knee joint in the direction of exten- sion and occurs when the line of action of the joint as a result of arthritic degeneration results in pro- tibiofemoral reaction force vector passes posteri- orly to the axis of knee flexion-extension (i.e., ,I when the external moment tends to cause knee flexion). Activation b,\\' the knee cxtensors is re- found gait deviations. One possible pathological gait pat- quired to counterbalance the tendenc'y' for knee tern is Trendelenburg gait, which results from the failure flexion caused by the external flexion n~oment. In- of the hip abductors to produce a sufficient abductor mo- ternal moments arc assumed to be generated b\"\" ment during loading response and terminal stance. This the muscles, soft tissues, and joint contact rorce~ pattern is easily observed as a lateral drop of the pelvis on acting on the joint and are inferred from inverse the side opposite the weakness during stance on the dynamics calculations of external moments. As weak side. Another way of describing this pattern is ex- such, the internal m0111ent is an expression of the cessive adduction of the weak hip during stance phase. net effect of internal active and passive structures and is strictly accurate in the case where a muscle Another pathological gait pattern seen with abductor group is contracting unopposed by antagonist ac- weakness or coxofemoral pain is the lateral lurch. In this tivation. At certain periods during normal gait and for longer periods during gait in nlany pathologi- i pattern, the trunk is displaced toward the affected stance cal conditions, agonist-antagonist coactivation may be present. In such cases, reported values for , limb during loading response, where it remains through- net internal moments will underestimate the ac- out terminal stance. This is observed as excessive lateral tual muscular forces occurring. However, this ter- displacement of the trunk toward the affected side, The n1inology is prevalent in the literature and useful result of this gait deviation is to reduce the required hip for the calculation of other kinetic variables. Plots abductor moment by displacing the body's center of mass of the internal moments occurring about the hip, closer to the hip adduction-abduction rotation axis. knee, and ankle joints during level walking in Both of these gait deviations effectively reduce com- healthy adults are depicted in Figures l8-3 pressiori\" across the coxofemoral joint by reducing contrac- through 18-5 and 18-8. ! tion force of the hip abductors, thereby alleviating joint I pain. The Trendelenburg pattern is a simple mechanical I ._CreO_!s~_~u_lt~O_f.~h~iP~~a1_b~d.O.U~.c1.ti_Por weak_ness. The lateral_lurch is a. __ abductor weakness. _ _ I e

By the end of loading response, the peak hip ex- Nm/kg occurs. During terminal stance, a second lo lernal rotator moment of appro.ximately 0.18 Nm/kg amplitude extensor moment of 0.2 Nm/kg occu is achic\\'cd (Fig, 18-3C, bOllom), The eXlernal rota- (Case Slud\" 18-1), tor mOment gradually decreases until the middle of terminal stance. Throughout the remainder of ter~ As \\\\'as the case with adduction-abduction abo min'll stance and pre-swing, a slight hip internal ro- the knee, knee adduction-abduction moments a Lalor moment occurs, controlled primarily through bone and soft tissu constraints. Therefore, the terminology for the Knee moments nt the knee refers to passive restraints, n to n1uscular control. At initial contact, there is a small knee flexor mo- ment (Fig, 18-4A, boltom), During early midstance, An abductor moment persists about the kne an extensor moment peak of approximately 0.6 throughout stance with lwo peaks of approx mately 0.4 Nm/kg during loading response and te Gait Adaptation,; in an Individual With Anterior Cruciate Ligament Deficiency Some individuals with anterior crlJciate ligament (ACl) defi· tained in 10 to 15:0- of flexion throughout miclstance. Associ- ciency demonstrate a \"quadriceps avoidance\" galt pattem ated ':vith this motion adaptation is a marked decrease of the associated with reduction of the stance phase knee extensor knee extensor moment during the early stance phase (see moment by as much as 140% (Andriacchl & Birac, 1993). The corresponding right knee moment plot). angUlar motion and moment data plotted beJmv shov'.' just such a clinical example. This adaptation 15 hypothesized iO prevent unrestrained anterior translation of the tibia by the patellar wndon through The subject oi ihis analysis was a 60-year-old male who reduction in quadriceps aCiivation. EtvlG analysis of the quadriceps muscles in studies of ACl deficienCy is consistent had sustained a partial tear of the right ACl approximately \"''1ith this hypotheSIS. This effective behavioral mechanism to reduce mechanical instability of the knee seems to be subcon- 10 years prior to the gait analysis, The injury was not surgically SCIOUS on the part of injured subjects. However. it may be pos· repaired. The subject had minor complaints of functional sible to train individuals to use this adaptation in a conserva- deficits, primarily on descending siairs. tive management program for ACl injlJry (Andriachhi, 1993). The flexion-extension motion plot (average of three trials) of the affected right knee shows a flattening and a reduction of the support phase peak knee flexion. The knee is main· 80 50 70 ---- Unalfected llexion 40~ ......-- ._-- Unaffected - Affected flexion -Affected \"'~\" 60 :Es ,\"\" .... :'';\"\"; 50 -, C 30j -- ..'\"0c> 40 E'\" 20 C '0 30 1O~:0;; ~ c '''C\"\"\" 20 ·0 10 ~ ''c\"\" 0 '\" -10 0, -20j ,, 0 20 40 60 80 100 0 10 20 30 40 50 60 Gait Cycle ('%) Gait Cycle (%) Case Study Figure 18·1-1. Effect of anterior cruciate ligament injury on knee motion and moments about the flexion- extension axis. Data were obtained during three trials of walking at freely chosen velocity and averaged. The figure (left) shows the difference between the ACl-deficient knee (affected) and unaffected knee flexion angles. The figure (right) shows the corresponding knee moments with values greater than zero representing knee extensor moments and values less than zero representing knee flexor moments.

min'll stance (Fig. 18-4B, bottom). During mid~ Knee stance, the knee abductor moment decreases to approximately 0.2 Nm/kg. In individuals who During loading response, power absorption b achieve abduction (valgus) positions of the knee, the eccentrically contracting quadriceps contro the moment profile may' be shifted toward adduc- knee flexion (Fig. 18-8. bolloll1-llliddle). Durin tor moments, and midstance adductor moments early midstance, power generation b:v the co mayoccur. centrically contracting quadriceps extends th knee while the contralateral limb is engaged A knee internal rotator moment peak of 0.18 swing. During pre-swing, power absorption b Nm/kg occurs at the transition between loading re- the eccentrically' contracting quadriceps contro sponse and midstance. The knee rotation moment knee flexion \\\\'hile the stance limb unloads then reverses direction during the latter portion of preparation for swing and the transfer of bod midstance, reaching an external rotator moment weight onto the contralateral limb. During term peak of approximately' 0.15 Nm/kg during terminal nal swing, power absorption by the eccentrical stance. contracting hamstrings controls the forward a celeration of the swinging thigh, leg, and fo Ankle segments. Immediately after initial contact, there is a slight Ankle dorsiflexor (Le., flcxor) moment of approximately 0.2 Nm/kg about the ankle that rapidly rcverses to a During midstance, power absorption by the e plantarflexor (i.e., extensor) moment for the re- centrically contracting plantarflexors contro maindcr of stance (Fig. 18-5, bottom). The plan- the tibia as it rotates over the stationary foot (Fi tarflexor moment peak is approximately 1.6 Nm/kg 18-8, bottom right). During pre-swing, a hig at 45°;0 of the stride, or the latter portion or termi- magnitude power generation peak of 2 to nal stance. \\vatts/kg by' the concentrically contracting pla tarflexors represents approximately' two thirds JOINT POWER the total energy generated during walking and believed to contribute significantly to propulsio Joint power is defined as the product of joint an- in gait. gular velocity and the corresponding internal mo- ment at a given point in time and is expressed in WORK AND ENERGY TRANSFER watts/kg of body weight. It (luctuates continuously throughout the gait cyTle and can be either nega- v\\fork is defined as the integral of power with r tive or positive in value. Joint po\\ver indicates the spect to time and is expressed in Joules/kg generation or absorption of mechanical energy by body weight. \\Vork is an estimate of the flow muscle groups and other soft tissues. Profiles for mechanical energy from one bod)' segment to a joint power about the Flexion-extension axes dur- other and is used to determine overall mechan ing level walking in healthy adults are depicted in cal energy efficiency during gait. \\Vhen work Figure 18-8. positive in value, the internal moment and joi angular velocity are actirlg in the same directio Hip a concentric muscle contraction is indicate and mechanical energy' is being generated. ,\",Vh From initial contact through early' midstance, the work is negative in valuc, the internal mome concentrically contracting hip extensors generate and joint angular velocity are acting in opposi power to a peak of approximately I watt/kg (Fig. directions, an eccentric contraction is indicate 18-8, bottom left). From midstance to terminal and mechanical energy is being absorbed. Du stance, po\\ver absorption by' the eccentrically con- ing p'eriods of energy generation, the muscle tracting hip flexors controls the backward accelera- working on the limbs to produce movemen tion of the thigh segment until approximately 50% During periods of energy absorption, the lim of the stride. From pre-swing to mid-swing, p()\\ver are working on the muscles, which must the generation by' the concentrically contracting hip contract to resist the tendency for muscle elo Oexors acts to pull off the swinging limb. gation.

Muscular Control contact to the middle of loading response that pers off by the end loading response. The upp J\\tluscle activation patterns are also cyclic during fibers of the gluteus maximus and the glute gait (Figs, 18-9 through 18-11), Muscle contraction mcdius (and probably the gluteus minimus) type varies between the eccentric control of joint an~ crease activation intensity through loading gular accelerations, such as in hamstrings activa~ sponse and taper olT by the end of rnidstancc. T tion during terminal swing, and the concentric ini- postcrior fibers of the tensor fascia lata arc moc tiation of movement, such as in tibialis anterior crately activated at the onset of loading respon activation in prc~swing. In normal individuals, ago- while the anterior fibers become activated la nist-antagonist coactivation is of relatively short and persist into terminal stance. duration and occurs during periods of kinematic transition (e.g., terminal s\\ving to initial contact). During pre-swing and initial to mid-swing, t The presence of prolonged or out-or-phase agonist- hip Ilcxors act to advance the limb. particula antagonist coactivation during gait in individuals when walking velocity is changing. The adduct with pathology may indicate skeletal instability as longus is activated earliest in terminal stance a well as motor control deficiencies. persists the longest to earl~' mid-swing. The rect femoris is the second hip Oexor activatcd duri HIP pre-swing and remains activated a short time in early initial swing. Thc iliaclls, sartorius, and g During early stance phase, the hip extensors act cilis have short periods of activation predominan concentrically while the hip abductors stabilize during initial swing. the lateral aspect of lhe coxofemoral joint (Fig. The hip adducLOrs are activated during tran 18-9). The lower fibers or the gluteus maximus tions between stance and swing, as are the ha string muscle group. This activation pattern can show increasing activation intensity from initial interpreted as the dynamic control of the swingi .~ '2,,'& Gluteus maximus (upper) a;'j Gluteus maximus (lower) %# :£a.-:= % .~ Biceps femoris (long head) Stride evenlS IC MSI :'B TO Semimembranosus PSw ISw Slride inlelVals LR TSI - , ;;C~ Semitendinosus >' Adductor magnus ::@ Gluleus medius Tenser fascia lala Adductor longus Rectus femoris Gracilis Sartorius Iliacus IC MSw TSw Phasic pattern of electromyographic (EMG) activity of the tact; TO, toe off; LR, loading response; MSt. midstance; TSt muscles of the hip during level walking in healthy adults. terminal stance; PSw, pre-swing; JSw, initial swing; MSw, m Gray regions represent activation below 20% of maximum swing; and TSw; terminal swing. Adapted with permission fro voluntary contraction. Black regions represent activation Perry, 1. (1992). Gait Analysis: Normal and Pathological Function above 20% of maximum voluntary contraction. /C, initial con- Thorofare. NJ: SLACK Incorporated.

~\"~fu~.!~'I'~\"-I--ll-r-l--r~~[§';,~,:;'-~ Vaslus intermedius ~ ~- Vastus lateratis t-,~ Vaslus medialis longus ~ ~.wEl.~ VaSlu$ medialis oblique [f::'J~g]~':§\"- Reclus femoris b~. -~~ Biceps femoris (long head) Biceps femoris (short head) ~:\"i:i Semimembranosus ,,-2 Semitendinosus c2(,~~;:~i!t&;~t:.: Popliteus Gaslrocnemius Gracilis Sartorius Stride events Ie TO Ie Stride intervals LR MSt TSt PSw ISw MSw TSw Phasic pattern of eleetromyographic (EMG) activity of the tact; TO, toe oft; LR, loading response; M5t, midstance; T5t, muscles of the knee during level walking in healthy adults. terminal stance; P5w, pre-swing; 15w. initial swing; MSw, mid· Gray regions represent activation below 20% of maximum swing; and TSv.I, terminal swing. Adapted with permission from voluntary contraction. Black regions represent activation Perry, J. (992). Gail Analysis: Normal and PJ!hologlCill FunCtion. above 20% of maximum voluntary contraction. fe, initial (00- Thorofare. NJ: SLACK. limb that is tending to flex and abduct at the hip. Most of the harnstrings muscles are activated in late The function of the muscles during such periods is mid-swing or terminal swing. Their function at the to control the acceleration of the rotating joints to knee is probably to control the angular acceleration ensure the precise placcrnent of the fOOL on the sup· into knee extension. This is consistent with their pre- port surface in anticipation of the upcoming stance sUllled action at the hip, or the control of hip flexion in phase. This explains lhe hamstrings and adductor preparation for the upcoming stance phase. The short magnus activity during terminal swing. head of the biceps femoris is activated earlier than are the other hamstrings muscles in early mid-swing and KNEE probably assists in flexing the knee for foot c1ean:mcc. During stance phase, the quadriceps muscle group The gracilis and sarlorius muscles also may con- (vasti) is relied on to control the tendency for knee tribute to swing phase knee flexion when they are ac- nexion collapse with weight acceptance and single tivated during late pre-swing, initial swing, and early limb support (Fig. 18-10). This muscle group is acti- mid-swing. Ho\\Vevel~ these muscles may very well be vated during terminal swing and then acts eccentri- acting as primary hip ncxors during this period. cally during \\veight acceptance as the knee rotates from the fully extended position at initial contact to ANKLE AND FOOT its peak support phase flexion of approximately 20° during loading response. Thereafter. the quadriceps Talocrural Joint act concentrically to extend the knee through early midstance as the bod)/s center of mass is raised ver- From EMG sludies on the muscles that cross the an- tically over the supporting 11mb and the anterior ori- kle, the dorsiflexor muscles are shown to be firing entation of the ground reaction force vector pre- concentrically during swing to allow for foot clear- cludes the need for furlher Illuscular control of knee ance and eccentrically during loading response to flexion. control the placement of the foot by ankle plan- tarflexion (Fig. 18-1 1). The plantarflexors are con- sistently firing eccentrically during stance to conrrol ~::L ...'~-.' .~.\"

==~~=:~- ~ i~--ll---II;:====:'~~_·~!=:-~c:. ~~~~:O:n~:~li~~iS longus Exlensor digitorum longus h., . \" TI Soleus I Fx:;sI ~. 01 I Gastrocnemius --\"''/»''\"'J;O~~';.;..;.1'.:.!',',;1~~::>'J'S'';; Posterior tibialis Flexor digitorum longus I Flexor halluc is longus Peroneus longus ;:;;';,,\"k\"ir~'::JM:,-iA:';~(';'/i;; \"'-: Peroneus brevis Abductor digiti quint! Abductor hallucis SUide events Ie MSI Flexor digilorum brevis Flexor hallucis brevis Stride intervals LA TO Ie TSt PS...J ISw MSw TSw Phasic pattern of electromyographic (EMG) activity of the mus- relative intensity as a percent of maximum voluntary cont cles of the ankle and foot during level walking in healthy adults. tion is not shown. Ie, initial contact; TO, toe off; LR. loadin Gray regions represent activation below 20% of maximum vol- sponse; MSt, midstance; TSr, terminal stance; PSw, pre-swi untary contraction. Black regions represent activation above ISw, initial swing; MSw, mid·swing; and TSw, terminal swin 20% of maximum voluntary contraction. Whire bars for the in- Adapted wirh permission from Perry. 1. (1992). Gait Analysis: No trinsic muscles of the foot indicate phasic data only for which and Pathological Function. Thorofare. Nt SLACK !ncorporared. the advancement of the tibia over the foot, to stabi- • Timing Effects on Gait lize the knee, and concentricall~' to assist push-off. Patterns The onset of muscle activity in the dorsillexors The peak electrical activity of the, dorsi flexors corresponds begins just prior to foot-ofr during pre-swing. to a high demand on the pretibial muscles as body weigh Winler and Yak (1987) reponed lhal these muscles is transferred onto the supporting fool. These muscles fire remain act.ive throughout swing and loading re- eccentrically to decelerate the rate of ankle plantarflexion sponse with peak electrical aCli\\'it~, seen in the first I50() of the gait c:vcle during weight acceptance, If there is inappropriate timing or insufficient force of (on when they must assist in controlling the fall or the traGion in the pretibial muscles, a drop-foot or foot-slap center of mass (Fig. 18-1 I). They are virtually silent during mid- and terminal stance (Box 18-3). gait pattern may be present. In addition, restrained ankle planta~~lexion provides some shock absorption during the The soleus and the mcdial head of the gastrocnc~ loading response. During swing, the tibialis anterior and millS begin activation at approximately fOlio of the the toe extensors function 10 dorsiflex the fOOl ior toe gait cycle, as single limb support begins (Fig. 18-11). clearance. loss of normal function in the pretibial muscle They continue firing throughout the stance phase during sINing frequently results in increased knee and hip until pre-swing, when single limb support ends and fleXion, or a steppage gait pattern. the opposite foot !lmkes contact with the ground. The lateral head or the gastrocnenlius may not be- gin activation until midstancc. During midslance, the plantarnexors eccentrically contract to restrain forward motion of the tibia. During terminal stance, as the heel begins Lo rise, the gastrocnemius contin-

ues to contract to begin active ankle plantarflcxion. In summary. during the first arc of plantarflexion During this phase. they provide a stable tibia over following initial contact, the dorsWexors arc fil\"ing ,,·hich the felllur may advance. Peak electrical activ- eccentl'i~ally to decelerate the rate of plantarnexio~ ity is seen at 50% of the gail cycle. and footfall onto the ground. During the first arc of dorsiflexion, the plantarflcxors ar~ firing eccentri- Although both the soleus and gastrocnemius cally to control the rate of dorsiflexion and tibial muscles share a common insertion. the role of the progression over the slationar~' fool. During the sec- soleus is somewhat different from that of the gas- ond arc of plantarflexion, just prior to weight trans- trocnemius because of the soleus' origin on the fer onto the opposite limb. the plantarflexors ar~ fir- tibia. The soleus, as a one-joint muscle, provides a ing to maintain walking velocity and step length. direct link between the tibia and the calcaneus and is thought to be the dominant decelerating plan- orFinally, during the last arc Illation, dorsiflexion tarflexion force. The gastrocnemius, as a two-joint muscle, plays a direct role in knee flexion during during swing. the dorsiflexors are firing concentri- midstance (Fig. 18-10). cally to allow foot clearance. The remaining five postelior muscles arc smaller Subtalar Joint in size and as perimalleolar muscles lie closer to the ankle joint (Fig. IS-II). These five muscles are tib- As the fOOL makes contact with the floor, subtalar ialis posteriOJ~ flexor hallucis longus, flexor digito- ev~rsion occurs as a shock·absorbing mechanism. rum longus, peroneus longus, and peroneus brevis. The inverters fire to dcceleralc this ~\\'ersion (Fig. These muscles playa greater role at the subtalar 18-11). The tibialis anterior acts to restrain the sub- joint and the foot than at the ankle but still create a talar joint during loading response. \\Vith its greatest plantarOexion force at the ankle joint. activity seen during loading response, the tibialis anterior is quiet by midstancc. The tibialis posterior begins firing at initial con~ tact and remains active through single limb stance Although the activation patterns of the tibialis pos~ until opposite initial contact. The flexor digitorum terior have been reported with various patlcr·ns of ac- longus begins firing next at opposite toe off and also thrity by different investigators, there is agreement continues until opposite initial contact. The flexor that it is a stance phase muscle. It becomes active hallucis longus is active from 25% of the gait cycle during loading response and remains active through- into pre-swing. Peroneus brevis and longus activity out stance until early pre-swing, Pen)' (1992) pro- begins early in stance and. continues into terminal posed that the activation during loading response stance or pre-swing. Note thal the activit)' in these provides early subtalar control. In addition. the vari- muscles is subject to considerable variation across ability of activity in this muscle may be indicative of individuals. its function as a reserve force to supplement insuffi- cient vanls control by the ankle Illuscles. The posterior calf muscles f'mction as a group and cease functioning by 5000 of the gait cycle when Soleus activity is seen during midstance with pro- opposite initial contact has occurred. The continua- gressively increasing activity in terminal stance. De- tion of plantarflexion past this point probably serves spite its major function as an ankle plantarllexor, to balance the body because the opposite foot has this muscle also has considerable il1\\'crsion lever- already accepted the body's weight. In a small group age, especially as a resull of its large cross-sectional of healthy adults, Sutherland et al. (1980) used a area. B.y pre-swing there is a 'rapid decline in activ- nerve block to the tibial nerve to further describe ity. and the muscle remains quiet during swing. The the role of the ankle plantarOexors, particularly the long loe Ilexors are the last in\\'cners to be activated. gastrocnemius and soleus during gait. They con- The flexor c1igitoruTll longus and the ncxor hallucis cluded that these muscles did not sen.:e as a propul- longus begin activation during midslancc and cease sion mechanism during pre-swing. Instead, they firing during pre-swing. concluded that these muscles should be thought of as maintaining fonvard progression, step length, The muscles that arc responsible for c\\·ersion at and gait symmetry. If the plantarnexors do not func- the subt<.llar joint are tht:: extensor digitorulll longus, tion normally. an increase in ankle dorsiflexion is peroneus tertius, peroneus longus, and peroneus bre- seen with a shortened step by the swinging limb. In vis. The first two lie anterior to the subtalarjoint axis, addition, the swinging limb strikes the ground pre- while the last two lie posterior to the subtalar joint maturely as a resuh of the lack of restraint of the axis. The extensor digitorul11 longus is active during tibial movement of the stance limb. loading response and quiet with the onset of mid-

stance. Little information is available aboLit the firing Su III lila rv of the peroneus tertius, but Perry (1992) reports sil1l~ Hal' timing as the extensor digitorurn longus. 1 Motion abollt the hip joint during gait occ all three planes: flexionMextension, addu The peroneus longus and brevis initiate activit)' abduction, and internalMexternal rotation. Fle during forefoot loading and demonstrate their peak extension is the primar:\\' motion occurring abo activity during terminal stance. Both the timing and knee joint during gait, although varus-valgus an intensity of the EMG signals in the peroneus brevis tational motions are present to a lesser extent. and longus arc closely coordinated. Activity in these muscles ceases by the I11iddle of pre-swing. The per- 2 Because of its bony' morphology', the talo oneus longus has peak electrical activity at 500/0 of joint undergoes only plantarflexion and dorsifl the gait cycle during push-ofr. during gait. Subtalar, midtarsal, and phala motion further assist in providing adaptation Midtarsal Joint support surface as well as rigidity for propulsi The midtarsal joint is supported primarily by the 3 The upper body', including the pelvis and t tibialis posterior. Because the activity of the long toe undergoes sinusoidal displacements in all flexors and the lateral plantar intrinsic muscles beM cardinal planes. The trunk and pelvis rotate gins before the toes flex, these muscles may well posite directions while the head usually rem contribute to the support of the midtarsal joint. stable. The s\\vinging of the arms involves sho Flexion-extension and rotation, elbow fle Forefoot and Interphalangeal Joints extension, and forearm pronationMsupination The flexor digitorum longus and the flexor halluc is 4 The gait cycle, or stride, is defined as the o longus begin activation during midstance and cease rence of an event on one lower limb until the firing during pre-swing. These muscles stabilize the occurrence of the same event on the same metatarsophalangeal joints and add toe support to limb. It is most typically demarcated by· sequ supplement forefoot support. The intrinsic muscles ipsilateral initial contact. Stance phase occ of the forefoot and interphalangeal joints include 60f?b of the stride and is divided into six events the abductor hallucis, adductor hallucis, flexor digi- riods: initial contact, loading response, mids tOlllIll brevis, flexor hallucis brevis, and abductor terminal stance, pre-swing, and toe off. Swing digiti quinti. These muscles become active at ap- occupies 40% of the stride and is divided into proximately 20 to 30% of the walking cycle and ods: initial swing, mid-swing, and terminal sw cease \\vhen the foot leaves the ground. These mus- cles aid in the stabilization of the longitudinal arch 5 Internal joint moments indicate the ne and of the toes at the metatarsophalangeal joint. ll1ent of force generated by muscles, bones, an sive soft tissues that counteract the tendenc Although the kinematics, kinetics, and muscular joint rotation caused by gravity. control of the major joints have been presented sepM arately, they are functionally interMrelated during 6 Joint po\\ver is the product of joint angul gait. The musculoskeletal system must undergo locit}, and the corresponding internal momen highly integrated, precisely coordinated actions in given point in time. It indicates the generati both timing and amplitude for efficient locomotion absorption of mechanical energy by muscle g to occur. This requires not only an intact muscu- and other soft tissues. loskeletal system, or physical plant, but also a func- tioning nervous system, or controller. The nervous 7 Coactivation of agonist-antagonist n system must be able to instantaneously assess perti- groups usually occurs during periods of kine nent aspects of the external and internal environM transition \\vhen a joint may be reversing the ments to act or respond appropriately to a variety of tion,of rotation. functional contexts. Motion limitations or other pathology of any participating joint will have a sub- 8 Motion limitations or disorders of moto sequent effect on all other participating joints. It is trol affecting any of the lower limb segment the complex integration of anatomy, biomechanics, potentially alter the patterns of movement an and muscular control that permits normal \\valking. tor control at all other joints during gait.

REFERENCES Pr.:rry, J. (1992J. Cai, A/llllysis: .vrOnr~Jo/Wrp!o{rjwallePd./lIJw/o.o\" ictll Flll/c- lioll. Andriacchi, T.P. &. Birac. D. (1993). Functional tcstirH! in the Thorobr\\.\", NJ: SLACK anterior cruciat~ liganH:lH-deficicnt knee. C[ill Orrlwp Rei Sutherbnd, D.H., Coopr.:r, L.. 6.: Dnnid, D. (1980), The role of Res. 288(March), -IO-·Ii. (he ankle plarllurfkxors in nornli.11 \\\\·alkin!.:. J BOlle Joiu! B<trr..-\\.E. (1998). Gail 'Inalysis. In J. Spivak & J. Zuckerman Surg, 6L\\(3), 354-363, - (Eds.), OrillOpacdics-..l Comprehellsive S/lulv Guide. New Whitllc. 1\\'1. W. (1991). Gair ..\\lUlly:;is: All hl/rodlleriol/. Oxford: York.: McGrnw·Hill. . Bu! lCrworl h·Hci IH:mann. Craik, R.L. & Oatis, C.r\\. (1995). Gait All(/Jy.~is: Theory (j}uj Ap- Winter, D.A. & Yak, I-I.J. (1987). EMG profiles during normal plicatioll. 51. Louis: !\\'losb\\'. human walking: Stric\\(.··lo·stride and inter.subject variabil· Gage, l.R. (1991). Cait illwivsis ill Cerebral Pals\\'. London: ity. ElectronellcepJw{oc,r efill NWl\"ophvsiol, 67, 402-41 I. Mac Keith Press.' . \\Vright, D.G\" Desai, S.M., & Henderson\", \\V.H. (1964). Action Lenhoff, 1\\·l.W., S,IlHnCI', TJ., Otis, J.e., C[ ,,1. (1996). Boot- of the subt<1lar and ankh~.j()jnt complex during the SWllCC strap simultaneous prediction and confidctH:c inlcn'a!s for ph<1sC of walking. J 1301/£' Johl/ Surg, 46M2), 361-382. gail data. Gait Post, -1(2). In. ...~ ;:z; <.,-.';;\".

Index Page numbers in italics denote figures; those followed by a t denote tables. iA ,gail cyck muscle ;;Ictio\\l (If. 228-229, compOIll.'lHS cA. 61-67, 62 136, 23i, ~53--456 ! A bands. 151. /52 stIlIClllr:l! inh.. r:IC:'lioll ~11ll0iH!. 67-6 joints and Illolion of. 225. 245-149 in IO:tdl.'d :lnd \\lnloadl.'d li~Sll(,. 1 anisotropy of. \\5\\ 'kinl.'malics of. 223.225 75-77, is ! Abdominal musdc:s axes in. 226. 242-143 c('lnpn:ssion (If ! in intra-nbdomin;d p[,~sslln:, 278-279 bipll~l:'lic rrL'ql l'c.::'POl1SI.' in. 71-7~ !.!;Iit CVl.,:k and, 226-228 biph:ISic stl'l·~s·n,\"-I;t:.;ntioll n:sponsc in spinal mov~mcn!. 265-266. 266 iig:,m~1ll ane! hone injllr\\' in. in. 73-7~ in spinal slabilit\\'. 278-281 2-15-249 ,. confincd. 70-71 strcnglhcning.276-277 stress propl.'nks ill, 6$-69 lension of. and spinal loading. 268-269 r::tllge of mOl ion in. 24-1 degi:lll.:ratioll of. 90 Abductor musch:.- group. hip slIrbce:: joinl motion in. 244-2-t5 ~h(llldrocvlc..' fUlH.:tion in, 91-92 faclOr\"!' I.·(;nsidcrl.'d ill. 00-91 slabilization, 207 kinl,:lics of. 249-251 malrix illtCgrilV in. 90-92 Ol>tW:ln Ilrilic, '()()-92 Abductor pollicis longus muscle. 374 lig:uth.'IlIS of. 245-249 Abrasive WC:\\I-. 88 l'Xp!;llH loading l.'ollligurmioll of. 70-7 Acccleromctrv.440 iUjUI;\" of. 245-249 lluid (lo\\\\, in, 69-75, ~I-SS load disll'ihulion hi, 25\\ fUllctions of. 61 ;\\cct,abululll.203-204 hv:dirw.61 musck :tclion of. in e.ail I.:H-Ie::. Inbrum of. 20-1 ~. h;bricoHion of. 81-83 loading p,lltcrn (Jf, 20-1 453-456 bnostl..'d. 85. 86, 86 transversc :Icc::tnblllar 1i£:ltllc::nl of. 20-1 Achilks tcndon, 236 - ShOl·\\\\'I.'~lr nnd m~'ch;\\Ilics of, 251-252 bOtilldal\\'. 83-H4, 8'+, 86 injury of. as~()ci<l{(,'d with high slrain I..'lasloh\\\"lrodvrwmir.:. $5 spr:lin in,lury of. 245-149 t\\:udcd' fluid 'in. ~5 I';;UC (nlfll1('rs). 114 !luid film. 82-83 sl;,bilitv or. 245-249 intl.'f'Sliliallhlid pn::ssllriwtion in. kincmntics of. 249-250 sl:ltic ~illal\\'sis or. 250 86-88 Acromioclnviclllnr joint, 319 and subwl:tr ,join I 11'101ion, 226, mLxl'd. S-I-86. 85 molecular organ;z:llion of. 61-69 analOlllV/killcm;'I'tics of. 321-322 12t\\. 230 joinl (.'oll'lIX'n~')li(Jn in. 446 PCI'Il1l.':lhililV of. 74-75 Actin fihllllents. 149-150 Ankk- Il'lOl'\\isc. 223. 242 arI1lngcmcnt in sarcomen:. 150. 150 (i.puq)OS('S 61 in musch:~ cormaclion. 153-155 Annulus fibroslls, 258 shl.':u' ~Il\\di(.'s of. 77-$.0 Adhesive wear. S8 of cervical illICI'\\'Crldlr:'t1 disc. 292 SllllC1l1l:11 dcfc..·cls of, ('\":lllsed b\\' \\\\'c::ac ADI (,:ltJalltode1114lJ intc['\\,:tl). 302. slrUClure :Ind c::omp(lsiti(Ht ol'. 61-69 tClIsioll in. 258 sUl'f:u.:r.: of. 804. 84-85 303.303 Anll.'rior crlldal~ Jigalllclll (ACL) swdlin!.! behavior of. SO-$I ll.'nsik' ~(rl.'$s,sll':Lill curve for, 76 A~!lrccan(s) fUtlClion of. 195-196 lripll:tsic bioltlCdl:lllic'll bl.'ll~IViol' of. g:lil :lc:l:lptaljon~ inddkicncy of, 450 -aging and i)1n.lctur~\\1 \\'al'iation of. RO-Sl 65.67 iujurvof. 113. 16S uniaxi:tltcnsion on. 7S-77 '~ts~ol,:blc::d wilh tr<tum'l. 195 bOllle-brush mock-I of. 66, 67 viscoelaslic bdlil\\'ior of. 70 in km'~ :\\nhroplasty, ... JS-416 molecular cOmposilion of. 65 now-irl(h.:p~·tl(\"-·nt.70 postsurgical rcp:tir of. 16S intrjn~ic. 70 slnlctural variations of. 65. 67 Anlioecuhilis matll\\.'SSI:!'. 434-l35 wr.::\\!· of. 0$-90 Aging. <lnd biomr.:chanical prope::nic::s colbgcn-nro1coglyC:11l rcslxII1SC 10. Apical IigamclHs. 29{) of arlicular cartibgc. 65. 67 SS-90 of bone. 53-5~ Arch«(.'s} of ligaments, 115 dcfl.'cts :lIlcl. 89-90 of tcndons. I 15 of fOOl. 235-236 iltlP~ICI lo:tding in. 89 Airbag injudcs, of ccr·Yil...nJ spinc, intcrr:\\(:bl. SS collapse of. 236 AtlalllO:\\xial SCgmcnt. 2S8-290 311-312 of h~lIld, 362 coupled motion of. 299 Alar ligamems. 290 AI'\\:<I It)OIll('nt of inertia, 47-4S inst:lbilitv of. wilhout fr:lclun:. 303 r.lIl£,c o(motioll of. .297-29~ Anconeus OlllSCh:. 350 Armrest suppor!. 427 Allmltodcnl:\\l iIHt..'I'V:11 (/\\DI). 301. 303. 3 activitv of. 351 :\\tlas n'r1I..'bnl. 287. 288-290 Al'lllrodesis Axis \\'(,'I'Ic::br:l. 287. 290 Angle or' ante\\'crsion, of fcllloml head. :Uld dcn~. 288. 290 cClyical. 308-311 Axonal 1r:IIl~pOn syslclns, 127 204-205 Axons. 127 spinal. 306. 30S Angular kincm:Hic analysis. 440 AnhroplaslY. 401-402 45 Anisotropy. 36 arllcrior cl1.tdatt.: ligmnenl ill I\\nl.'I.', Ankle joil1l. 223 415-416 axis of. cmpidcal. 242-243 goals of. 40 I ball-and-sockel.229-230 in biomcchanics of sianding. 4:22-H4 hip. 401--107 boncs of. 223, 225. 245-249 knr.:r.:. -107--412 dynamic mwlysis of. 251 gait cycle kincmalics of. 226-228. poslerior crudale ligament in knec.:. 445-447 -112-414 gait cycle kinetics of. 249-251, 451 Articular ('al'lila~c :lIlisolrOpi(' plnpcnks of. 63. 6-(\"65 bioltlt.'chnnic::nl hch;;\\\\'iol'of. 69-81 hiph;l~k C\\'l..'l.'P response:: in. 71-72 biphask Sil'l.'Ss-rc!a,xalioll rl.'sponsc in. 73-74 : (I> ----------------------------------

B bi0l11cch;lllk;11 propcnil:s or. 31-36 C~lllalicuJi. 27-28 Ba~k belts. biolllcchankal l.:ff..:clin,'ucss C:.nct::llolls hOlll..·. 29 anisOl.-opic.3-4, 36 of. 281 rtlcchanienl properties of. 33, 292-293 Back muscles, in spin:l! rlIo~'clllcnL 266 cotlljxlrcd to olher maled:tls..13-34, stress-s!l\"ain cun'c (If, 34 Back rcsl suppOrt 35f Cnpsular ligaments, spinal. 260 Cardiac 11ll1Sdc, 149 and loading of lumbar spine. 269, 271 diffcrcnc(,.·s 1.Jl.:twten bont:: typ('s, 33-34 Backrest support, 428 C:u\"I':d bones. 359 B~lsc Siunits. 19 biphask propc::nit::s of, 27-29. 31 C<ll'pal tunnel. 359 ClI'pal tunnel syndrome. fllcdian nerve definitions. lOt composition and stJ'UClurl..' of. 27-31, Bcd(s) in. 36~ 55 Caq)ol11l:tacarpal (Ci'vIC) jOilllS. 359. 379 fcatures of good. 433-H4 lying in, biorncclwnics of. 433--434 lllacrosl.:opic.29 of fing<:rs, 378-380 sitting in. biomechanics of. 434-B5 Biceps brachii. 350 microscopic. 29-30 of thumb. 380 C'II'PUS, 359 activit\\' of. 352 damage of (<.:I11.:nl linc::, 28 Biceps lllllScI.... extrinsic factol's, 56 orCelltl:r pressure (COP), 421-422 in elbow kinetics, 350 in sholllder kinetics. 322-324, intrinsic bctors, 57 Cervical anhrodesis fatigue or. in r(\"'pctitivc loading. ~5-47 alllcrior approach in, 308 330, 350 gmft malerials in, 30S-309 geometry of, 47-51 indications for, 308 BBii~ul;lvlcccahn·all6i5c~. -' poslc!\"ior, 309-311 he<llin!? of studies of, 309-31 I ddonn~Hion modes in. 7 inrn~c(Ul'(, fixation, 391-392 c1:1stil\".- ddonnation in, 10-11 Cen:ic<lllamilll:ClOm\\'. 305-306. 30i cndurnncc in.m:ll..: ..ial. 14-15 hypertrophy of, undt::r platt:, 52, 53 Ccrvk~ll plming systems. 310 CL'r\"ic;t! spine ('quilibrilllll conditions in. 6 pCI·iproslht.:lk loss of. 406-407 allalonw of. 2~7-292 fatigue' in. material. 14-15 n.:modcling of. ~\\lld biomechanic:ll ;IIHcllcx'ion of. in silling position, force Vectors in, 3-t frcc-body di.tgrams in, 5-6. 6 behavi<ll~ 51-53 430-431 ;tpplied biomechanics or. 305-311 ll1<l1crial propcnies based on sln:\"$S- slri.:nglh and stiffness of. 31-36 :lnhrodesis or. 306-311. 30S biomcchanical mOdt:lilH! of. 287 slrain di:lgrams in. 13 nging t:fft.:cIs 011. 53-54 dl.'compression of. 305-306. 307 mOllH:llt vectors in, 4-5 fi,\\,ltiol1 of. 308-311 of rnusl.:llioskeleta! svstem, 15 bone Icn2th innucncc 011. 48 function of. 287 (:aHus form~llion and incrc;:asl,.' in, fllBclionallillil or. 296. 297 applied biollicchallics, 15 injury of. 311-314 joints. 15 48-49 instabilitv or. 301-305 tissut's and Slll.lctltfCS. 15 instan! C~IllCl\" or Illotion or. 293 Newton's bws in. 5 cross sectional an'a influence on. illll.'r\",:nL·br'll discs of, 288. 291-292 nomlnl SU\"~tin in. S-9. /0 norl11~ll stress in. 7-8. 8 47-48 medl;tllical projK'nies of, 293 plastic ddolTIlation in, 10-11 kin(,Ol;tlics of. 296.297 principal stn:ss in. 13-1~ fatigue.: in, in l\"e.:pctili\\·I..·loading. scalars in. 3 abnormal. 300-30 I shear· strain in. 8-9. /0 45-·.:7 coupled motion in, 299-301 she.lr stress in, 7-8, 9 l';lIl~C of motion, 297-298 s!<ltics in, 6-7 n.:modding ;\\lld. 51-53 slllLce joilll llIolion, 298, 299 strains in, normal and sheal~ 8-9. 10 stresS'Slrain diagrams ill, 9-10,10 surgical prex.'(.'(!ures thaI wcakL'n, 49-51 ligaments of. 288 stresses in stlllcture ~Illd composition of. 27-31.55 mechanical properties of, 293 normnl and shear. 7-8 pdlldpal, 13-14 macroscopic. 29 motion of. 287, 288, 290 tensors in. 3 ~\\hnonnal. 300-301 IOrqlle \\,('ctors in. 4-5 microscopic, 29-30 p;tradoxlc;tl. 300-301 \\'I..·clors ill, 3 \\'ascukll' ~)'SICIll of. 30. 31 dscoebsticity in. 11-13 l1lotion scgmelH or. 288. 290-291 Bone, 17.~7-48 Bone densilv. 33 llluscular medwnics of, 293-29-4 aging and changes in. 53-5~ and <lging·. 53-54 l'lcur:1i lllc::chanics of. 294-296 anisolwpic propenks of. 3-1. 36 neurologic,injury in. 294-296 biomcdwnicaJ beh:l\\'ior of. 37 [lolle mass OSSl.:OllS SIlU(:tur~s of. 28H-291 bending !onds and, 40-~2 stabilit\\' of. 301-305 combined loads nnd, 42-43 ;'It\"~C(i ~\"'cndgdh!\"t'r. '\\l1d 53 . i.J tl\"::IUI1l~ 10. 311-314 compressive loads and, 37-38, 39 '51-52 - \\'i,'nebntc of, 288-291 gcomt:tJ')' of bonc and, 47-51 llHISclc ,Jctidtv and stress Bone milll:r;ll, 27 mechanical propl.'rtics of. 292-293 llflcO\\'L'l'lebnd joints of, 291 distl\"ibulioll in. 43-~4 BOlle rCllloddin2. 51. 52 C!londrocvles, in articular cani1a!!.l.l, 61,62 n:pctili\\\"(:')onding and, ..5....-17 body weight :tl~d bone m:ISS in, 51. 51-52 degenel:al i\\'i,~ clwnges and. 91':92 sh\"'~lI' londing ~lIld. 33-W Chondroitin SlIlf<ll(: sll71in mtc dependency of. ~4--45. -16 C;lse stud\\' of. 52 in aniculat' cal'lilagc. 65-69 stn.:ss di,Sll·ibution in. and muscle in cerdcal nuclclls plilposus, 292- implanls ·<lnd. 52-53 Chopan's joilll motion, 230 \"clivity.43-l4 Clavicle, 322 tensik·lo<ldini!. and. 37. 38 Boosted lubrication, 85. 86 CI<lw loes, 237 lorsionallo;uiing and. 42 Bootstrap ilt.:ratioll, 4~3 Click-clack phenOIIl(·non. IUlllbopdvic. 428 Co:tJ-hanllnl..'r grip. 3S-I BoundalY lubl'ic;ltion. 81 of aniculal' c~\\nib2c. 83-8.... $6 BI71chialis Illuscle. 350. 37... ncti\\'itv of. 352 BI\"::K:hio;'adialis llluscle, 350 activil)' of. 352 Brooks type. cc,,'kal arthroc!L-:,is. 309-310 Bunched lisi. 38.. BUllions. 233 shoe wear and de\\'Clopmcnt of. 251-252 C CJ-C7 vcrtebrnc. 297-298 Cadence. 443 Cnlcancocuboid joint. 229. 230 Clkancofibular Jigaml.:lll. 245-2-16 flillciioll or. 2-J9¥ injlll)' to, 245-249 Calf muscles. ~55 Callus formation. <lnd incrense in bone stl\"l,,'ngth . . .8 - 4 9

ColI~gcn Diarthrodinl joints, 61 Epincul\"ium, 129, 130 anisotropic properties of. 288 uoicondvl.w, 378 Epilcllon, lOS of nrticulul' cnnilage. 61. 62 Digital Oc.\\OI' tendon sheath pulk,.\\· Equilibl\"illHl condition.s, 6 distribution of, 62, 64 systcm, 368-369. 370 Erl1S palsy. 135 mechanical properties of. 62-65, 288 Dil~ital rays. 362 Ercttor spinae lllllsck·s. 265-266 rnOlcCllkll\" composition of, 61-62, 63 in arched batk in prone position. ~ollatel:al liganwnts of. 369, 371 extc:nsor and flexor systems of. 375 stl1.lctLlral alignment. in loaded and 276,277 unlo:ldcd tissue. 75-77.78 c.,tcnsor systellls of. \"371-374 f()f\"cCS of. in standing, 268-269 Sll1.lCIUrnl organization of. 61-63. 6..1- flexor tendons heath pulley systelll of. strengthcning c.,crdses fOl~ 276-277 65.67-69 368-369.370 E·X·Io\"'arcdission~\" ankle joint in. 2-19-251 type II. 62-63 joints of, 378-380, 379 nnd prolCoglycan m:urix of :Irticubr muscles of. extrinsic and imrinsic, londs on fOOl in, 240-241, 2-12 c:lrlilagc, 67-69 375.3751 loads on lumbar spine in, 276-277 response 10 weal- of. $8-90 mllscular mechanisms of. 375 Extcnsor digilOnlln longus. ..l55 in tendon ~machmcnl of muscle lO llumbcl\"ing of. 359 Extensor mechanism injury. kllcc.199 bone, 149 l-::lIl!!C of n~otion of, 378-380 Extensor s\\,sh.:m Dist~\\I-in(Crpll:llangcnl(DIP) join\\S, 362 of tendons nnd Iigamcnu'i of digitai rays, 371-374, 375 mcwbolic turnover of. 105 range of motion of. 378-379 of toes, 455 molecular composition of, 103-104. tendinous mechanisms of, 371-374 of wrist. 350. 374 105 Donnan equilibrillll1 ion distribution Extraccllular matrix (ECi\\l), structural alignment of. in loaded law, 68 of aniClll,u\" c<lnilage. 61 and unloaded tisslie. 109 Donnan osmotic pn:.'SSUI·C cqu'Hion. 81 in dc~t'ncl'::\\li\\'(,.' conditions, 90-92 Slll.lctlll~1 organizalion of. 104--105. 106 Donnan osmotic prcssufc Llleol)\". 67, 68 Illole~u!araggregates and propertie type I. 103-10~ DOI'Sa! intcrcarp;:ll ligament. 368 67-69 type II, in cen'ical nucleus pulposus. 292 Dorsal root g\"lIlglion. 128, 131 of tendons :\\nd ligaments, 103, 10-1 types of. 62-63 Dorsal scnson' roots. 128. 131 visc:odastic properties of. 288 Dorsiflexion. 2-t-l, 453-454 Collagen fibers, 104. 105 D\\\"namic she.lf modulus. 78-79 F Colla!!cn fibrils, 10-1-105 D;\"namic tripod, 383 F'lcct capsular lig;:l11u::nts. 288 Compact bone, 29 Dynamics, 185 F:lccteclOmy, pani:\\J, 306 Component inst,-\\bility, 301-302 F~ICl.:tS Computer workst<ltion, biomechanics of of ccrvical intcl'ycrlcbl\"al joints, 290- sitting at, 427 E of intervcrtd>n:tl joints. 259-260, 26 Concentric muscle contraction, 159 Eccentric muscle contr:\\ction, 159 F\"lscicles Conversions. 51 units, 221,23 Elastic deformation. 10-11 of muscle libcrs,I..l9-150 Coracohumeral lig'lments. 321,325-327 Elastic material bdlavior, I I of periphcral nerves, 129, 130 Conic..d bone. 29 Elasticitv. 33 F..lIiguc fractllr\\.'s, 45--47 mcchanical properties of, 33, 35. EI'-lstin, of tendons and ligamellls.l 05 F'-ltigue WCal\", 88 292-293 Elbow joint. 3-t 1 of articular cartilage, 88-90 stress-strain curvc for, 33. 3-1 nnatom.,.· of. 3-11-342 of bone, in rcpt.'titi~'c loading, -t5-47 yidd points in, 34-36 articula\"tions of. 3-11-3-12 evclic Crecp and recovcry tCSt, 12 forccs gencratcd in. 352 . of hip jlmsthcscs. ..t02-W3 Crcep response forces on articular surface of. 353 of knee pmsthcscs. 407-10S biphasic. in articubr l..'artilage, 71-72 fracture disloc'-ltion of. 3..l9 nwtcri..I, 1-1,14-15 in tendons and ligamt.:nts, Ill. 112 injury of. 347-350 of prostheses, 392. 393. 402--103, I Cross-bridges. of myosin filaments, lateral epil.:ondylitis, 352 407-408 153-155 kinematics of Femoral head, 203, 204 I Fcmoml intcnrocharlteric fracture, 2 Cnlciate IigHmcnts, 195 carrvin\" nn\"le 345 346 remoral neck, 204 I cent'er;r r07:ttion. 343, 34-1 C.voeflihc ifpalpiu~Lolsethcscs. 402-403 aging and ch\"lIlgcs in. 205-207 I f1exion·cxtcnsion, 3-12-3-t3 in hip anhropbsty. -104-106 of knee prosl heses, -107--108 pmnation/supination. 343-345 neck-to-shaft ..Hlgle of. 20-1-205 stability.3-t5-350 Fencing grip, 38..l D valgus position, 345 FG (f'lst twitch glycolytiC) fibers, 165 de Quc!\"\\'ain's Icnosyno\\'itis. 374- kinctics of. 350-355 Fibroblasls, '103.10-1 Dccodn,65 muscular :malon1\\' of. 350 Fibulolalm' joint. 223. 225 Decubitus. 434-435 Fick's principle. 236 Ddormmioll. 7 or.muscular mech;:ulics of. 350 Fingers. 359, 362 clcctromyogm,phic an'-llysis 350 reaction for<:c calculations for, 353-355 ofbone,31-36 stability of. 345, 347-350 in prehensile hand function, 3~2-3 ;1 clnstic and plastic, 10-11 Ekctrogoniol11etry, 440 range of motion of. 378-380 Deltoid ligaments, of ankle, 245-246 Ekctromyogrnphic (Ei'v1G) .analysis. 440 Fixation plate ['nihl!\"c, 393 rI Elel.:tromyography. 156 Flexion-relaxation phenomenon, 265- function of. 249 End plalc, 258 Flexor digilOl1.lll1 lon!!us, -l55, 456 I injury lO, 249 Endomysium. 149-150.150 Flexor hallucis I()ngu~. 455. 456 Deltoid muscle. 329-330 Endoneudum. 129. 130 Fh:xOl\" s\\\"stcm Dens, 288,290 Endosteum, 28. 30 Derivcd 51 units, 19 Endotenon. 104. 108 of digital r:lyS, 368-369, 370. 375 with spccial names, ddinitions. 201 Endurance,material,I-I-15 of tocsJfordoot. 237-::238, 453-456 Devic(,.· f:-tti£!.uc, 392, 393 of wlist. 350. 359. 374 Diabetes nldlitlls. h,'ndons .md lig3mel\\ls Enlrapmenl, nerve. 132. 133 Flexor tendon sheath pulley syst,,·m. Epimysium. 149-150,150 368-369.370 II in, 116-117 ~' -\"\"\"\"\"\"\"\"\"\"\"\"\"'=-\"\"\"\"\"\"~\".,.-\"---.-..\"...\",..=-\"\"\"\",,,,,;==;r.-~~~~f!'!!%-1Jk=-~~,~_\",-zt\"'\". £€{\"--,..=~ _~cs. -.\"-0\"\"_ ~~ \"y(' '?cP5'~\" \".' -,- ;<O.7'__::'·~._'c>\"'5 .... ];g,~~.±gA...1 ~'$--.-~.

Fluid·(ilm lubril'illion. 82 Kil'sdllll.'r wire. 394 Gk'rlOhuflll,:rnl joinl, 3/9 of :lrticular c~ll·tibge. 82-83 ori';':IHcd polYrlll.'r. 393 -394 capsule of. 325. 326 plate. 395-396 gk.·llOid bbnllll of. 323-324 FOCi (fasl twitch oxidali\\\"l.' glycolYlic) scn.'\\\\·, 394-396 Jibers. 165-167 spin.1I impbnt. 3'17 Inslabilil\\' of. 327 slapk 39-1 Fool wir..:-. 393 kincmilli~.s of. 322-327 'In~llomy of. 223. 22-1 \\\\\"in: lensiolli!l!!;twisli!H!.. 393-394 lig~lInenl CUlling sludies of. 327 in biomechanics of st:lndin!.!. 422---+24 fn:e bod.\\' di;lgn~ll(s), 5-6. 6 ligi\\lllt:nls of. 325-317 extrinsic nluscks of. 233-2.34. 237-238 Frec-bod~' diagl,llllS IO~Hls on, 335-336 ill sialics, 18~-190 I't::lclion force on. 337 fn.'c·body di;lgi41111 or. 250 Free-body tcchniqul.:, for coplan.lr forces, Glenoid,323 Glc.:noid bbnllH, 323-324 gait cycle ground reaclive fon.:cs on. 18~-·190 injuries involving, 32~ 240-24 I Cil~'cosaminoglycans (GAGs), 27 simplified. 211-213 in artkulnr C:irtilnge, 65-67 g.lil cycle kin(~n}[ltics or, 226-229, chondl\"Oitin sulfal~. 65-69 G ker~lin sulfale. 65-69 445-447 Gracilis. in 2:tit cvde. 453 Gail. ~39 Grafts - . g~\\it cycle leg rot:nion ,Ind. 226. 228 an~IIOJllicnl Illolion in. 439 gnil cycle mus(,:lc nelioH of. 22X-229, ~1l!~lIl~lr kincmalic:s of. 443-149 in cer\\'ic:11 nnhrO(ksis. 308-309 c\\'~I(\" of. 4\"0-457 tcndons ~Ind lig;:lInl;.·nls in, 117-118 236. 237. ~53-156 !.!.r<l\\\\'!h of. 223, 225 ,fc\\'i:ltions of. -149 H Joints of. 223. 22-J H zonc. 151. 152 killcll1:llics of. 223. 225 join! killL'lllatics of, 443-449 1·1.llil'<:lx C!:llllpS, ccn'iC~11 ;:lnhrodcsis. joint moments in. 449 anklL' :and suhtaku: 226. 228. 230 joint POWt:I' in. -151 309-310. 3// gait cycle and, 226-229 H:lllux IHuscubr co1l11'o1 or, 452-156 hallux. 231-234 joint 1I10tion of. 231-134. 233 lesser lOe, 233-234 segml.:ntal kinclks of. 449-431 'tendon posit ions in. 238 111I.'lat'-\\l\"sal bn.::lk, 228. 229 w~rk and Clll'!'!!V tr~\\nsfi.:r in. 451 I-I;lilux dgidu:-,. ~32 prorwlion/supination. 223, 226 G~dt ~Ul:d\\'sis. mc~t'h()ds of. 439-4-10 lbllux \\';\\Igus. 23 L 233 subml;u: 229-230. 23/ Gail c\\·d~. 4-10~4 I shoew~.':lr and dcvclormL'nt of. 251-252 !:\\rsomctat.lr:-al and inlen;ll·sal. <lnkle killenwlics ill. 226-22~. 218. in spntin injury. 2-J7 Hammer tocs. 237 230-231, 232 445-447 sho(,'wc:\\!' ;\\Ild development of. 251-252 trnnS\\'i.·I\"SL' l;lrS:ll, 229-231 ankle kinctics in, 249-251. 45! H;llllsirings, function in knec joint. kin~lics of, 238-2-11 ankk: muscle ;Iclion in, 228-229. 236, g,til cyde and ground n::aeti\\'c fore..::-. 196.453 237. 453-456 l·blle!.359 in. 2..10-24 I bootstrap iwrmions of. .;)43 running ane!, 240-241 c(\"utcr of mass in. hod\\'. 4-18-149 arches of. 362 slJOcwc-ar and, 240 cydil' btiguc of hip p,:osth..:-ses in. articulations of. 359. 362 blood supply of. 365 sol'ltissut:s lind, 241-242, 2..J3 402-403 capillal;\" prcssurc within. 365 medial longitudinal arch of. 235-236 e~'c1ic bligu(' of kncc proslh~sl.'s in. muscle aClion of. 236-238, 236/ control mcchanisms of. 365 .107-408 g~it cycle and, ~53~56 dorsilkxioll in, 453-454 aCli\\'e, 375 rnusdl..· injury :lna disorders or. 136-~3:$ fOOl kinematics in. 226-228, 4-15-447 ll1uscllhu: 375 foot Illuscle action in. 228-229, 232, passive. 368-37-\\ shoewcar <lnd m....ch:mics or. 2..m. immobile unit of. 378 236. 237. 453--456 2S 1-252 ground l'1.':tclin: forcl;.'s in. 240-241 joints of. 36/.378,379 soft tissues of, 241-242.1';3 hip kinemalics in. 4-'3 FoOl prcssure :Ill;,lysis, 4-10 H!!amenlS of. 371-374 aging alld, 206-207. 208 -dieil~11 colbll'l\"l!. 369..HI Fon.:c: plalc an:dysis, 440 gcndL'r differcnces and. 215 digilal flexor lendon shl.\":llh pulle.\" Force ,·cctOl'S. 3-4 hip kinclics in. 449-150. -1-19-151 SV$h:m of. 368-369. 370 dt:g('neraliw p:lthology and. 449 \\'obl\"phUL',371 For....ann. pron'llion and SUpill:ltioll. hip musd£: action in. 45~-453 376-377 kn..:-I.~ kinemalics in, 179-180, 444-445 lI1uscies of. 363l knl.'l: kindies in, 185-194,450-451 t:.\\lrinsic, 350. 362, 365, 375 Forefoot knee muscle action in, 453 intrinsic. 350. 362, 365. 37/,375 g.\\it cycle kinematics of, 446~47 leg rOl;ltion in. 226. 228 g;til cyclc muscle :activity of. 456 lo\\\\\"er k'l! muscle action in. 232 nerVeS of. 362. 36-1-365 mllscllli~' acti\\'~ltion in. 452-456 OSSt.'lIS sll1t<:lttrC of. 361. 362 Fnlcturl.\"{s) p~:l\\'ic kinc.:matics in, 4~7-148 prdlcnsik function patt(''I\"llS, 382-3S5 hone healing in. 391-392 st~lllCt: phasl.~ of. 227 r.1ngc of Illotion of digital rays. brittlc, 35. 36 s\\\\'ing phase of. 227 ,hlclite, 35,36 tillle·disl;lIlce \\·ari.1bles of, 4-12-443 378-3$0 fmiguc,45-47 tnlnk kincmatlcs in. 447--I-iS repelil!\\'(: Ill(ltion injlll;\" or. 37-1 Iwnlin!!. uhnlsolHld Irc;HI11\\.'nl for. 392 w:dking ~tnd mnning s..:-nsOl)· specialization of palmar, 364-365 yield ,;oint of hOlle. 35, 36 comparison of. 226, 227 skirt of. 362 forccs on ankli: in, 251 tendons of, 371-374 f\"acturc fixation, 391 kne~: flexion in. 179-180 \\\\Tisl mOl ion nnd motion of. 381 boll\\.' hcaling in, 391-392 Gallic (~'p\\.;'. ccrvicill anllrodcsis. 309-310 Ha\\'cI-sian canal. 27 Gastroclll'rnillS mU5ck 454~55 Havasi'lIl S\\'SICIll, 27-28 hone 1110\\'CIll\\.'n! in. 39\\ Gill,gl~'moidjoilll, 34\\ Hl.\"acl,·cst :l;lde, -129-130 deviccs and Illl..'lhods of. 393-397 ev:t1uation of. 393 Heel pml, 2-1 i -242 goals of, 391-397 sllr!.!.ical factors in. 392-393 tl\"<\\<iitional methods of. 391 Fr.H:lllfC fixation c!C\\'iccs!mclhods, 393 cxtrmncdullm;:. 396-397 btiguc of. 392. 393 hip, 396-397 intcnncdulhll;:, 396-397

Hdf~1 tl~st. 184.186 11lIerfacbl we;lr. 88 f(.nt..'l,.' :mhroplast.\\· i-kmodialysis, tendons and ligamems in. Interosseous ligamL'nt. of ankh,'. 245-246 :ITlh.'rior cnl<.·iatc ligan1L'll1 in, 415--4 117 Intcl'osseous membl-:mc:.', of dbo\\\\'. conformity of femoral and tibial Hinged joint. 3~ I 348-350 components in ...H4 bicondylar. 373 injury of. <\"Ind r;lelia] migr;uion. 352 conslr~lillt <k'sign in. 415 Hip ill,th,:oplasty Interosst..'olls mllsd~s. 237 forcl.·s acting on, 401--402. 407-408. - bone n:moddin~ around. 52-53 Intcrphal::mgeal (lP) joints hinged proStheses in, ... 15 celllented tOI~1 hip rcph\\CCmcnl . .:lOS joinl lint.: dc'·;ltion in. 412 forces ;:lctin~ on, 401-402 of fim::ers, 362. 365-366, 378-379 ·1l1edial.laleralload disll'jbulioll in. !!.ail and sttl~lics of forces 011, 402-403 of thl~mb. 380 of tocs, 233-234 409-411 joint recollstruction and biomechanics I:::~lit cvdL' kinematics of. 447 patcllofcmoral joint loading ill. 411 . of. 404-406 gait c;'c1e muscle activity of. 436 polyc(hy!cllL' cbmagc modes in. 415 peri prosthetic bont: loss in, 406-407 Ill1crspinous ligaments, 260. 288 posteriol' Cnlciate ligament in. 412- rot~\\tional moments <Inc! bone Intcrstitial fluid pressuriziltion, in tihi:d component loosL'ning in. 409- in-growth in. 403. 404 ~lniClll<lr cnrtilage. 86-88 Knr.:,'(.' joint stem position within femoral canal in. Intel't~II\"Sal joilll mOl ion, 230-231, 233-234 bio;nl.·dwniGII analvsis of. 177-178 406 Intenransn:I'se ligamel1ts. 2SS cnpsuh:: of. 195 . Hip joint. 203 11Hl.'lycl..tcbml discs, 258 dcrangelllt:llts of. 182-1 t\\5 ::lcc(;lbulum of. 203-204 cervical. 288, 291 dynan~ics of. 190-19';, 197-199 \"ging and changes in. 205-207. 208. 217 :.nnulus fibrosus of. 292 nc:don of anatonw of. 203 loading. 291 injury in. 196 , ball-and-socket configunltion of. 203, lllc:.'chaniC;l1 propt..'nics of. 293 rc:.\"lctiOll forcl\"s in. 197-19$ 204,205 nucleus puJpOStlS of. 292 in SlancL' phase of l1.mning/walkin (knamics of Illmb~u' 179-180 -gait and gcndcr differences. 213. ~l~in~ of. 259 fn.:e·hod,\" dii:l2rmn of. /89 215-217 c~mpositiollof. 258-259 gait cycle kin~lllatics of. 179-180. wilh instrumented o::lil pialI..'. 217-219 degC\"l1cmtionnl changt..'s in. 259 -t4.........t.45 wilh insI11.1mcillcd prosthesis. loading distribution in. 25S gnil cycle kincticsoL 185-194. 45Q-. 216-217 lo;:\\(ling f;lilllrc of. 271-273 g<tit i.:yck muscle aClion of. ... 53 c-,tern;ll support, nnd dyn;\\lnic~ of, in rniddlt: age, 259 menisci of. 193-194 218-219 prL'ssure on. 258-259 muscle action on. gait c~·de and, btiglle fracture of. 2/i in \\'OlI!h. 259 196. 453 lliechailical propL'nit::s of. 293 femoral head of. 203. 204 patella of. 196-197 femoral neck of. 204-205. 206 Imr:l·abdominal prL'ssul'e (lAP) l\";:1l)2C of motion of. 179-180 rr~lcturc h.\\atioll devices, 396-397 ,HlCl!oading of lumbar spinl.'. 272-273 :-;i.\\ 'kgrees of freedom of motion, 1 in st~lbility of lurnbal' spinc, 278-279 s(~lbilitv of. 194-196 fracturc of. 21 i kinenwtics of. 205-208. 209, Inlnlflls~,1 muscle spineles. typl.\"s of. 169 statics ·of. 188-190, 197-199 mll~e of motion, 206-107 Intrinsic minimlls condition. 234 SIl'lICturc of, 177 surf.'1ce joint motion. 207-208 Intrinsic muscles. of foot, 233-23.... surf<lce joilH 1Tl00ion of. 180-187 kinetics of, 208-213. 2/5 237-238 ll.'ndons and ligamen(s of. 177. 19\"' ex lerna I forces on body in single-leg Isoinertial muscle contl-:lction, 159 Knee meniscectollw, 90, 9/ stance. 212 IsokinL'lic mllsclt: cOll(l'aclion, 159 Kyphosis. 267-268: 287-288 free-body diagr;llll of lower Isometric rnusclt: comnlction. 159 pathology of cervical. 29..J or:cxtremity. 21~ Isotonic muscle conu71ction. 159 posturc and. 421-425 in Slalics of standing, 26S mm'Clllt:'nlS 207 muscle action in g;:lit cycle. -I52......t.53 muscles of, posterior. 265-266 J and spin~t1 motion. 266-267 Joint Illomt.'nts. gait cycle. 449 L static analysis of, 209-213 Joint power. g:.il c.velc. 451 Labrum, 203 HUlllcromdinl nniclll;ltion, 341-342 Joinls Laclln;:\\C, 27. 28 kinematics of, 342-345 capsule of. 103 Lamellae. 27-29 HUllleroulnar aniculation. 341~342 dvnamic analvsis of. 185, 187 Lamclbr bOlle. 29-30. 30 kinematics of. 342-345 Lnrnini.:clOmv. cervical. 305-306, 30i kinematics or\". 178-179 Humerus. anicular slIrf;lcc r;:\\nge of motion, 179-180 Lmcrnl c:ollaiL'ralligalllcllt (I.el.), 195 distal. 341-342 surface joint mot ion. 180-18! :IIHltOm)\" of. 347, 3413 proximal. 322-323 killL'tics of. 185.187 kinematics of. 347-348 Hyaline ;,rticular canilage. 6 i statics :malvsis of. 185. 187 Laler,,1 epicondylitis. 352 Hvaluronic articular c;:\\rtilage. 65-67. 69 types of. 6'· Lalt..'ml m~lsscs. 288 -inhomogeneity of, with c<~\"rtilagc 1.;I(t..'r\"lit'., 4.12 depth. 7-1 K Ll'g.crossing. while silting, -t32......t.33 Hydrodynamic lubricmion, 82 KCI\";\\tin sulfate Lifting Hysteresis, 110, III bilCk belts in, drectiven~ss of. 2S1 in ;:mieu!;!.!\" e;lrtila!!c. 65-69 b\"ncling moment produced in. 272 in cer'deal nuelcus-pulposlls. 192 .lI1d c:m·ying, spinal loading in. 271- I Kint:nmtic inslability. 301-302 andlo\\\\' back paill. 269-271, 273 I band. lSI. 152 Kinematics. 17S tumb'lr spinutloading in. 271-273 Immobiliz..'\\tion/cxcrcisc, tendons and range of motion.179-ISO tedllliqlle and. 272-275 ligaments in, 115-116 sud\"aec joint motion. 180-ISI l\"L'pe;:lted. spinallonding in, 271-273 Instilllt center tcchlliquc, t80-181 Kinetic ;malysis. 185. lS7 stoop and squat.Jorce comp,lI'isons Intercm-pal joinls, 359 Kinelics, 185, 187 in, 274 _,_ \" ......._ s.

Li~aments muscle control of. 264-267 sllpplementm-y units of. 19 lkxor and extensor, 265-266 svmbols of. unit. 2IT biornec!wnical bch;'lvior of, lOS Iawntl nexor and rotation, 266 Midcarpal joint. 359, 365-366 physiologicnl londing and. 110-111 pelvic motion and. 266-267 Midtarsal joint viscoclnstic. I 11-1 12 gait cycle kinem<ltics of. 4-16 st;-abilityof. 278-281 gait cycle musclc activity of. 456 hiofllcchanicnl pmpcnics of. 109-110 external stabilization in, 279. 281 Moment vectors. 4-5 in aging. J 15 intra-abdominal pressure in, 278-279 Motion segment, 257-260 in diabetc:'s mellitlls, 116-117 trunk muscle co·contnlction in, 279 anterior portion of. 258-259 in gl1lfts. 117-1 J8 cervic.tl, 288, 290-291, 296 in hClllodial:ysis, 117 static analysis of landing, 268-273 facets of. louding, 259-260 in immobilization/exercise. ca1c:uh\\tions in, 272-275 115-116 companllive, in standing, sitting, ligamentum llavum of. 259 in nonsteroidal anti·inf1<:Hllmatory reclining, 269-271 drug lise. 117 intra-abdominal pressure .md, 273 longitudinal ligaments of, 259 in pregnancy'!postpnrtum in lifting, 271-273 posterior portion of, 259-260 range of motion of, 262-263 period, 115 Lumbosacral joint, \"nel spinal motion, stnlctllres of. 257-260 in steroid lise. I 17 surface joint motion of. 262-263 components of. 103-108, \\031 266-267 trans\\,crse section of. 258 d~lsticit\\' of. 110 Lunate, 359 Motor cells, 127-128, /29 fUflctim; of, 103 Luschka. joints of. 291 ,\\110101' nerw, 127-128. /29 injury ;-and failure mech\"nisms of. Lying in bcd, biomechanics of :\\>10tor neuron, 127-128. /29 . • 112-1IS, 123 ;\\,10tor spinal nerve roots, 131 crih:rion of conformitv in, 434 ;\\'1uhiplicalion factors, SI units, 21( cl.tssificntion of. 114 and decubitus ulcer de\"elopment, MllSclc(s) innervation of. 107 postunll and phasic, 421-422 inscl·tion of. into bone. 108 434--435 types of, 149 stl1.lclural nIT;l.ngcmt:nt in mattress support in, 433-434 ~'Iusclc fali2uc, 279 pillow support in, 433 !\\'1l1scle fibc;\"$ fiber, 104-105~ /06 contrnction of. 153-155 OlllCl~ 108 M cross section of. /52 v\"sclllnr svstem of. 106-107 cross sectional amltolllV of. /53 viscoelasticity of. 11 1-112 illt line, 151, 152 disuse ..lnd immobilization effects on. in barle-ligaments complex, 111-112 M:lgerl type, cervical arthrodesis_ Lig::ullcnlUl11 llavul11. 259 167-168 elasticit\\' of. 110,260 309-310 lllvofibrils of. 149-154 hypenn~)phyof. 260 i\\Jlalleoli, 242 p!~ysica.ltminingeffects on, 168-169 Line;.\\!- strain, 32 Mallet wcs, 237 stl1.lctmnl organization of. ~'1alcrial propcnies, bascd on Slress~ Link. 180 149-150, /52 Lisfranc's joint motion, 230-231 strain diagrams. 13 types of. 165-167 Lisfranc's ·ligament. 231 M;.l\\lress support, 433-434 dt:tcnnination of. 166-167 Lond-defOlTIlalion curve and development of decubitus ulcers, MlIsclIloskclctnl system. 15 for fibl'Ous stl1.lcture, 31, 32 434-435 applied biomechanics of. 15 p\"ramelcrs of. 32 Medial collateral ligament (MCL),195 joints of. 15 usefulness of. 32 nnmomy of. 345, 347 'tissues and stll.lctures of. 15 Loading patterns kinematics of. 345, 347 Musculotendinous unit, 156 and mechanical behavior Mvdin sheath. 127-128, /30 Medi;-ao longitudinal nrch, 235-236 M;·ofibrils. 149-150 of articular c.milage, 70-80 collapse of. 236 composition of. 149 of bone. 37-43 - secondary to posterior tibial contraction of. 153-155 dcficicncv, 237, 238 organii'.ation of. 149-150 and mechanical pl'Operlies, 36 models of. 235\"':236 sarcomeric, 149 Longitudinalligamcnls, spirml. 259, windlass effect on, 235-236 striated ~m-;,ulgeihcnt of. 149-150 Mvosin filaments, 149-150 260,288 Mcdinn ncn'c, 362. 364 'in muscle contraction, 153-155 in carpaltunne1 syndrome. 364 sarcomeric alTangement of. /50. 151 Longus colli muscle. 288 Lordosis, 267-268, 287-288 Mcnisccctomv, knee, 90. 9/ N Menisci, of kn~e, 193-194 posture and, 421-425 Met.lc;.trpal heads, 369 Nebulin filaments. 149-150 in S!<:llics of standing. 268 Metacarpals, 359 sarcomeric annogcment of, 151 l.ow back pain Metac<'\\l'Pophalangeal (iv1CP) joints. 359, .md lifting, 269-271. 273 Neck-to-shaft angle. of femoral nc..'Ck. strengthening exercises fol', 276-277 362,369,370-371 204-205 Lubrici7l, 84-85, 86 of fingers, 378-379 I.umbal' spine range of motion of. 378-379 in hip arthroplasty, 404-406 axial load on. in w~llkillg. 273-274, of thumb. 380 Ncl'YC fibcl~ Sll1.lcture and function. 127 and vohlr plate. 371 Ncl'YOUS s\\,stt:m, 127 275. 276 Metmnfsal bl'eak motion, 228, 229 Newton's bws, 5 back I-CSt SUppOl-t ;:lnd loading of. Metmarsophalangcal joillls, 232, 233-234 NodesofRan\\'iel~ 127-128,/30 ~.'tetric syslem, 19 Nonsteroidal anti-innammatol)' drug usc. 269.271 b<lsC units of. 19 dynamic analysis of loading, 273-276 conversion of units of, 221, 23 tcndons and Iigamcnts in. 117 definition of units of. 201 Normal strain, 8-9. /0 in exercises, 276-277 derived units of, 19 Nornwl stress. 7-8, 8 in walking, 273-274 mllltiplication faclOrs in, 211 kinematics of. 260 nnming of units after scientists, 21-23. llluscle action, 264-267 nmge of motion, 262-263 211 surfnce joint motion, 262-263 prefixes used in. lInie 211 micro(bmage to, in cOlllpressiv~ specially named units of. 20-21 loading:, 272

I Nucleus pu!posus, 258 Phasic muscles, 421-422 Radial nerve, 362 of cervical intcl'ycrtcbral discs. 292 Pibl)· ridges, 365 Radius I under pressure, 258-259 Pillow suPPOrt, in bed. 433 in sciatic pain, 14..4 Pitching. biomechanics of. 336 distal. articulation of. 359 1 Plantar aponeurosis, 233 scrc\\\\' homc mechanism of. 352 o Plantar calluses, 233-234 Range of motion. 179-180 I Plantar fascia, action of. 235-236 Rcaching, biomechanics of, 425 OccipilOccrvical joint, 288-290 Plillltar ligaments, 235-236 Resorption of bone, under plate, 52. I inst~lbililV of. 302, 303,304, 305 Plantadlexion, 244 Rocker bollom foot dcfomlitr, 236 Rol.ItOl' cuff musculaturt::, 330 I Occiput conlplex, 288-290 muscle activity in. 453-456 ROlatOr cuff teal~ 334 Open section defect. 50-51 Plantarflexors, 4-53-456 RolatOr interval, 330 ! Optoelectronic techniques, of gait Plaslic deformalion, to-II Posterior cruciate ligamenl, in knee 5 ,i- analysis, 440 Sarcolemma, 149, /50. 153 Osteoarthritis arthroplasty, 412-414 f Posture, 421-425 Sarcomere. 149-150, /52 chondrocvtC' ~bnormalitics in, 92 alTangcment of. and force produc cOIl(l-ihllling factors in. 91 free-body diagrams of slooped, 424 162-163 nod degenerative changes in a1·ticulal· muscles involved in. 421-422 contraction of myofibrils in. 153-1 statics of. 268-269 filamcnt composition of. 150-152 canilage. 90. 9/,92 POWCI' gIip. 382. 383 myofibril arrangement in, 149-150 OSlcoblasls. 30 Precision grip, 383 OsteoclasIs, 30 Prclixes, SI units, 211 Sarcopla~mic reticulum, 152, /53 Ostcocytcs. 27, 28. 30 Pregnancy/postpartum period, tendons Sartorius. in gail cycle, 453 OSlwns, 27-28 Scalars. 3 and ligaments in. t 15 Scapula cracking of. 35, 36 Prehensilc hand function dcbonding of. 3~-36 muscles acting on. 330-331 Osteophyte formation. 352 factors in. 382 rotation of. 336 pattellls of. 382 Sc'lpulothoracic articulation, 3/9 p kinem<llics/anatomy of. 317-318 bunched fist, 38-1 Schwann cclls, 127-128, 130 P\"lmar extrinsic ligaments. 366 coal-hammer grip. 384 Schw,annom,as, 135 Palmar plate, 371 dynamic tripod. 383 Sciatic pain, 137 P;llmar radiocarpnl ligaments, 366 fencing grip, 384 nucleus pulposLlsin, 144 Paraspinal muscles. 265-266 power grip, 382, 383 SCIWORA (spinal cord injury witho Par~ltenon. 108 precision grip, 383 Patella, 196-197 Principal stress, 13-14 radiognlphic abnorm,llilies) Prominens, 290 295-296 fracture of. 199 Pronalor quadratus muscle. 350 Screw-horne mechanism. 182-183, P:;\\Iellofemoral joint. 185. /87 PronalOr teres muscle, 350 /84. 352 Pronator teres tendon. 3i4 Seming angle, 429-430 instant center of. /86 Proteoglycans (PGs). 27 Sensory nerve, t 27-129 loading in knec arthroplasty. 411 in aggregate solution dom'lin. 67-68 Sensol~' spinal nen'c roOtS, 131 static and dynamic analysis of. in articular cartilage. 65 Sharpcy's pelforating fibers, 108 disruption of matl'i.x, 88-90 Shear slrain, 8-9, /0, 32 197-199 moleculnr composilion of. 65-67 Shear stress, 7-8, 9 surface joint motion of, 181-185 stnlctural interaction of. 67-69. Shocwcar. and biomechanics of Pectoralis major muscles, 329-330 fool. 240. 251-232 Pcdiclcs. of cervical vertebrac. 290-291 75-77 Shouldcl: 319 Pelvic tilt. and spinal statics. 268-269. wash out of. 88, 89 injuries of. 323-324 in cen..ical nucleus pulposus. 292 rotator cuff lear. 334 425-426 of tendons and lig:UllCntS. 105-106 SLAP lesion. 324 Pelvis Proximal interphalang\"'al (PIP) joints. subacromial impingement synd 334 gait cycle kinem.ltics of. 447-448 362,374 instability of. 327 kinematics of. 266-267 lkxor tendon sheath pulley system joint capsule of. 325-327 Pcrimalleobl\" muscles, 455 joinls/articulations of. 319 Perimysium. 149-150 of,370 acromioclavicular, 321-322 Perineurium. 129. /30 in passive control of wrist, 365-366 glenohumeral. 322-327 Periosteum. 28, 30 range of motion of. 378-379 scapulothoracic. 327-328 Peripheral nerves. 127. /28 tendinous mechanisms of. 371-374 stcmoclavicuI<\\r. 320-321 biomechanical behavior of. 133-139 Psoas muscle. 265-266 kinematics of. 319-328 blood-nerve bmTicr in, 133 lens ion of, and spinal loading, spinal conlIibution lO. 328 compressive injury of, 135-136, /45 kinelics of, 328-337 269-271 extension, 334 critical prcssure levels in. 136 external rotation, 333-334 mechanical aspects of. 137-139 Q forward elevation. 332-333 presstll-c application modes in. 136 Quadralus lumbomnl muscle. 265-266 glenohumeral joint loads in. pressure duration \\·5 pl·cssure Icvel Quadliceps 335-336 internal rotation. 334 in. 139 function of, in knee joint, 196. pitching, 336 connective tissue of. 129, /30 in gait cycle. 453 scapulolhoracic. 334-335 funclion of. 127-129 in knee motion, 196-199 Illvdinaled, 127-129. /30 st;..lclure of. 127-129. /29. /30 R tensile injtll)· of. 134-135 Radial arter\\\" 365 \\·asclilar svstcm of. 129-131 Radial collaieralligament. 366 Peroneal ml;sc!cs. 237. 455-456 Pcs phll1us. 237. 238 Phalanges, of fingers, 359.36/.362 l~!lo. .~~c

S h o u l d e l ' - - c o l l 1i H l t e d tensile o\\·el\"1o<ld of. 161-163 St:.Iil- climbing, lower leg in. 190 ligaments of. 325-317 types of, 149 Sumcc phase, ..\\-10-4-11 muscul<lture of, 329-331 work performed by, 149, ISg-160 londs on foot in. 239-240 mechanics of, 331-337 dynamic. 159-160 St:.\\nding. biortlcch.lllics of osseous .motom\\' of. 319-328 static, 159 Celltel: of pressure (COPl in, 421-42.2 range of motion' of. 3! 9 Skeletal system, 27 eye and hand movemcnt in. 42.4-425 Sf metric system, 19 SLAP lesi~n, 324 flal joint \\'S ball and socket joint in. SI units Slip lines, 34 426-427 base. 19 Smooth mllsch.~. 149 foot and ankle joilll in. 422--U.t. conversion of. 221. 23 SO (slow twitch oxidative) fibcl's.165-167 mass center of gravity in. 421-422 definitions of. 20t Soleus muscle . ..\\5-1, 455, 456 peh·ic kinematics in, 425-426 derived. 19 Spinal anhrodesis, 306, 308 postural and phasic mllscles in, 421-422 multiplication factors and, Zit Spinal cord injury reaching while, -U5 named artci' scienlists, 21-23, 21t and cen'icnl mechanics, 294-296 stooped-posture while, -124 prefixes of, 21t without radiogl'aphic abnOlll1ulitics. Stmics.6-7. 185. 187 specially named, 20-21 295-296 free-bock dia~r~lIns in, 188-190 suppkmcntm}'. 19 Spinal implnnt li.'\\ation dcvict:s. 397 Sttcrs Rlll~ of '[hirds, 303 svlllbois for, 211 Spinal n('\",..e(s), 127, /28 Step, 442 Sitting, biomechanics of. 427-431 embryologic development of. 131 Step frequency, 443 amm::st support in. 427 peripheral, 127 SICP length, ..\\42 backn..'st support in, ..\\28 roots of. 127, 131 Step width, 442 in bcd, 434-435 Spinal nerve roOts. /28, /3/ S('modaviclll~u- joint. 3/9 at cOlllpUler workstation . ..\\27 analOm'· of, 131-13.2 :'Ul<ltomv/kinematics of. 320-321 nnd decubitus ulcer dc,·c1opmcllt. -134 biomechanic:.ll behavior of. 139-144 Steroid ll~e. tendons and lignmcnts ill. hei.ld :'llltcncxion in, -n0-431 blood-nCIYC barrit.'r in, 133 117 hend rcst angle in, .t.29-430 compression injury of. 132 Strain leg-crossing in, 432-.03 compression of linc:'I1'.32 maximnl SUppOI-t in, -128-429 expedmelllai. 141-1..\\2 nOll1131, 8-9. /0 neck pnin in. -130-431 expaimcntal chronic, 1-13-1-1-1 I:\\tc depcndem:y of bone. 4-l--I5,-I6 problem arei.IS in. 431~32 multiplc k'\\'ds of. 143 sh..:.ar. 8-9, /0. 32 seating :.lngle in, ..\\28-431 Strain gauge, 33 onset raw of. 141-143 at tabk:, 430-..\\31 connectivl: tissul: of. 131 Stress, 32 Skeletal muscle, 149-150 motor, 131 normal. 7-8 activity of. :.md sO'ess distribution in ph:,-'siology ()f.131-131 principal. 13-14 ·bone, 43-..\\4 sensory. 131 shc:.u·. 7-8, 9 .au3chment of. lO bone. 149 vascular system of. 132-133 units of measurClllent of. 31 banding pa[[em of. 149-153 Spin;ll slcnosis. 295 Strl.·ss r:.liser. 49-50 biomcchanical behavior of. 160- I65 Spine. 257-258 Siress-relaxation experiment, /3 composition of, muscle fiber, 149-153, Clllyature or, 267-268, 2$7 Slress-rdax:.uion response 165-167 fatigue fracturcs of. 271 of articular c.:artilallc. 73-7-1 contraction of fllnctionnlunit of. 257-260 iof tendons and Iig;menls, III, // mechanics of. 156-160 (eSling, 296. 297 Stress-strain diagl.ll1ls, 9-10 molecul.u- basis of. 153-155 instnnt Center pathway of. 264 SU'ctch test, for subaxial instability, Slllllmntion :.md tet:.mi<:. 157-158 intcrycrtebmi discs of. 258, 28S. 304.305 typt:s of. (58-160 291. 293 Stride. 442-443 work types and, 158-160 kinematics of. 260, 301-30.2 Stridc analysis, 439-440 force production in, 160 muscle <:letion in. 264-267 Stride length, 442 fatigue crfect in, 164-165 range of motion in, 262-163 Stridc time, 442 fOfc:c,timc relationship of. 162 surface joint motion in. 262-263 Subacromial impingement syndrome. 334 length-tension relationship of. kinematics of shouldel\" and. 319-328 Subaxinl spine. 287. 290-291 160-161 kinetics of. 274-180 COli pled motion of, 299-300 10:ld-\"elocil)' relationship of. 161-162 ligaments of. 257, 260. 293 inswbilit\\' of. 303-305 muscle architecture cffLoct in, 162-163 loads on diagnosis checklist for, 3051 pn:stl'Ctching effect in, 163 dvnamic analvsis of. 273-280 stretch test for. 304, 305 temp<:falUrC effect in, 163-16-1 sianding, 268~269 fange of Illotion of. 297-298 function of. 149 st<:ltic annlvsis of. 268-273 Subtalar joint functional unit of. 155-156 mechanic:.l! j>roperties of components !:!:'lit c\\'cle kinematics of. 4-15-146 injurit.'s of. 167 of. 292-296 gtlit c)'c!c muscle :.lcti\"ity of. 455-456 extrinsic factors in, /72 motion of. 263-.264 ligaments of. 249 intrinsic faclors in, /7/ motion segment of. 257-260, 288 motion of. 229-231 innervation of. /54 muscles in movement of, 264-267 ankle and, 226, 228, 230, 249, motor unit of. 155-156 flexor and e.xtensor, 265-266 445-446 I musculOlcndinous unit of. 156 lateral flexor and rotation. 266 Summation, 157 rcmodeling. 167 pelvic motion and. 266-267':\" Supin:.llor muscle. 350 disuse and immobilization in. neural dements of, 29-1-296 Supplemelllary SI units. 19 j 167-168 stability of, 301-302 definitions. lOt physicallraining in, 168-169 structure of. 257-260 Supraspinolls ligaments, 288 repair or. 167 vertebrae of. 287, 291-293 Surfact: joint motion, 180-181 I structurc and organization of. 149-153. Spondylolisthesis, 262 Swing phase. 440--141 170 Spring ligaments. 235-236 Symbols, 51 units. 211 I } I \"L,,·\"'-\"=.5=~.=~5'~_~\"'_=~,~_~=\",,\"\"\"''''''>~,'', =~\"'\",\"-=\"'''''',\",,~=.,Z:;'\"~\".' .'.'' \"'.)',,,...-..,....,.. ;\"'~.'P~:.\"':\"~.\",\"\",'';''Jf\"J,'l'r2'.~,.-';·~[,:·::\".,_\",.{;;,.·{.;o;,~;.,\"0V§._,.\"'~K<,',;:J1~?:.1iJ,\"4;'J~.=';\",'.

Syndesmotic ligaments. 223 scn.'w·llOme mechanism of, V . componenls ~)f. 245-246 182-183, /5,'4 \\'eclOrs, 3 Svndeslllotir.: stabilitv. of ankle, 249 statics of. 188 fon:e, 3-4 S~·novial joims. 61 . moment, 4-5 System Intemational d'Unites (SO, 19 surf'lee join[ motion of, 181-185 torque, 4-5 Tibioflblll~u· joint, 223, 225 Velocitv, 443 T Tibiofibular ligaments, 245-248 Ventrai/molor roots, /28, 131 l' system, 153 Vertdmlc, 287 l~)locrural joint. 245-246 injun· to, 245-249 failure of. loads causing, 271-273 TibicHalar joint, 223, 225 gait cycle kinematics of, 445 Titin filaments, 149-150 293 gait cvcle muscle action of. 453-455 mechanical properties of, 292-29 Talofil1lilar ligament(s), 245-248 arrangement in sarcomere, lSI Vertebral arthrodesis, 306, 308 injury to, 245-249 Toe(s) Vertebral bodies, 258 Talonavicular joint, 229, 230 cervical. 290 Talus. 241-242 claw, 237 Viscoelastic material behador,12 load distribution on, 25/ extensor muscles of. 233-234 Viscoelasticitv, 11-13 Tarsal joint motion, transvcrse, 229-231 cxtdnsic muscles of. 233-234 Volar plate, 3\"71 Tarsometatarsal joint motion, 230-231, great, 231-233 Volkmann's canals, 28, 30 hammer, 237 233-234 intrinsic muscles of, 233-234 W Tendons k'ssel~ joint motion of. 233-234 \\Vear, 88 mallet: 237 \\\\'eight, and bone mass, 51-52 biomechanical behavior of. 108 Toeing, -in and -out, 446 \\Vhi~plash s~·ndromc, 312-314 physiological loading and, 110-111 Torque vcctors, 4-5 \\Vindlass effect, on arch of foot, 23 viscoelastic. 111-112 Trabeculac, 28, 29 WollTs law, 51 Trabecular bone, 29 \\Voven bone, 29-30 biomechanic;:1! properties of. 109-110 TransfCl\" lesions, 233-234 Wrist joint. 359, 360 in aging, 115 Transverse ligament in diabetcs mellitus, 116-117 of acetabul\"um, 204 articulations of. 359 in grafts, 117-118 of atlas, instabilit\\\" of. 302, 303 blood supply of. 365 in hemodialysis, 117 Transvcrse tarsal joint, axes of. 23/ control mechanisms of in immobilization/cxercise, Trans\\\"crsc tarsal :joint motion, 115-li6 active. 374 in nonsteroidal anti-inflarmnatory 229-231 bonv, 365-366 drug use. 117 Transversus abdominis muscle, ]jga;l1entous, 366-368 in pregnancy/postpanum period, liS n;llscular, 374 in steroid usc, 117 278-279 passive, 365-368 Trendclenburg gnit pallern, 449 functional motion of, 380-381 components of, 103-108, 103r Trendelcnburg's test. 209 hand motion and motion of, 381 diffusional nutl'ition of. 107 Triangular flb~·ocartilagecomplex kinematics of. 375 elasticitvof, 110 flexion and extension, 376 functiOil of. 103 (TFCC) forearm pronation and supinatio injury and failure mechanisms of. components of, 359,36/,366.368 376-377 112-115, /21 kinematics of wrist and, 368 radial and ulnar deviation, 376, innervation of. 107 radial migration and, 348-350, 352 kinetics of, 380-381 insertion of, into bone, 108 Triceps muscle, 350, 352 ligaments of. 366-367, 367t muscle attachment to bone, 149 Triquctnlln, 359 structural arrangement of Tl\"ochlcoginglymoid joint, 341 ~d()rsal extrinsic, 366 Tnlchoid joint, 341 intl·insic, 366, 368 fiber, 104-105, /06 Tropocollagen moleculcs, 61-62 palmar extrinsic, 366 outer, 108 Tropomyosin, in skeletal muscle, 150 palmar radiocarpal. 366 tensilc strength of, compared to Troponin, in skeletal muscle, ISO muscles of. 363r Trunk extrinsic and intrinsic, 350, 36 muscle, 114-115 llexor and extensor muscles of, 279 Ilexor and extensor, 374-376 \\\"ascular svstem of, 106-107 gait cvcle kinematics of. 447-448 nelyeS of. 362, 364-365 viscoelasticitv of, 111-112 ;nuscie co-contraction in, 279, 280 osscus slructUI\"e of. 359, 360 Tenosynovitis, ~le Ouen\"ain's. 374 range of motion of, 375-377 Tensors, 3 T\"\\ve I muscle fibers. 165-167 rep~titive motion injury of. 374 Terminal cisternae, 152. /53 Type IlA muscle fibers, 165-167 tendons of. 374-376 Tetanic muscle contraction, 157-158 tl'iangular fibrocanilage complex Thumb Type 1m musclc fIbers, 165-167 functional motion of, 380 368 in prehensile hand functions, 383-385 U Tibial plateau, stresses on, 193-194 Ulna, 341-342 y Tibialis muscles, 237 in gait cvcle, 455-456 distaL articulation of, 359 Yield point, 34 Tibiol·emo;·al joint Ulnar arter\\\", 365 Young's modulus, 33 derangel11e;1ts of. 182-185 Ulnar nen\"~, 364 dvnamics of, 190-194 Ulnocarpal complex, 359 z I-ielfet test of. 184, /86 Ulnocarpal space, 359 instant ccnter pathway of. 181-182 Uncinate processes, of cervical \\\"ertebrae. Z lille(s). 151, /52 range of motion of, 179-180 291 LJncovertebral joints, of cervical vel\"teb·rae, 291 LJnicondylnr dianhroidal joints, 378