["DDIII-~ callsc lhese mcthods ~lre highly technical and com plex, a simpler method evolved in the nineteen Range of Tiblofemoral Joint Motion In the ccnL'It'\\\\, Is sLillus~d (Reuleau,\\\\, 1876), This m~,h() called the installt cl.?nter techniqul.', allows surfa Sagittal Plane During Common Activities joinl 1l1Olion lO be analyzed in the sagiual an froolal planes but not in the transverse plane. T I Range of Motion instant center l~chniqLle pl{)vides a description from Knee Extension the rch'tive uniplanar motion of two adjacent se ments or n body and the direction of displaceme to Knee Flexion (Degrees) - - - - - - - - - - - - - - - - ,Activity or the contact points bct\\\\\\\\'L~cn these segmcnts, Walking 0-67\\\" The skeldal portion 01\\\" a body segment is called \\\"\\\"I link. As one link rotaLes ~il){H1l the other. al any i Climbing stairs stum then... is a point that docs nOl mov(:, that is, point thal has h'ro velocil.V. This point conslitlli Descending stairs 0-90 an instantaneous cenLer of motion, or instant ce Sitting down 0-93 tel: The instant center is found b.\\\\' identirying t displacen1cnt (If two points on a link as the li Tying a shoe 0-106 moves from one position to another in relation to adjacl.?nt link, which is considered to he stalionar lifting an object 0-117 The points on thl.' moving link in its original po tion and in its displaced position arc designated ';Dillil lrom Kel1clkamp el al. (1970i. fvlean for 22 subjects. A slight a graph and lines an.' drawn connecling the two se ddiercncc was found bel'.'.'een r19ht \\\"nc! lei! knees (mean for right of points. The pCl-pcndicular bisectors or these tw knee 68.1\u00b0, nW,ln for left knee 66,r). lines are then drawn. The intersection or the pe \\\"These and sub:.equerH date' from lauberllhal Cl al. (1972). Mean for 30 subjects. pendicular bisectors is thc instant ccntcl: Clinir::'lll~', a path\\\\\\\\'a~' of the instant center for Kcltclkamp's group (1970) also mcasurcd motion in the frontal plane during walking. In nearly all of -joint call be determined b\\\\' takinQ successive roen the 22 subjects, maximal abduction of the tibia was observed during extension at heel slrike and at the ~~ beginning of the stance phase; maximal adduction occurred as the knee \\\\Vas flexed during the swing genograms of the joint in dilTcrent positions (usual phase. The total amount of abduction and adduc- 10\u00b0 apart) throughout the range of motion in o tion averaged 11\u00b0. plane and applying the Rculcaux melhod for locali Values for the rangc of motion o!\\\" the tibiofemoral the inslanl center 1'01' each intcrv[ll or motion. joint in the sagittal plane during several comn101l \\\\Vhcn the instant center palhway has been dete activities arc presented in Table 7-1. l'vlaximal knee flexion occurs during lifting. A range of motion mined 1'01' joint motion in one plane, the surfa joint mol ion C[ln be described, For each intel'val I'rol11 full extcnsion to at least II r 01' flcxion ap- motion, the point at which the joint surfaces ma pears to be required for an individual to carry out contact is located on the roentgenograms lIsed f the activities of daily living in a normal manner. Any the instant center analysis, and a line is drawn frol restriction of knee motion can be compensated for by increased motion in other joints. In studying the 1Imtl!JIJI--~ -~~-,-~----~ range of libiofcmoral joint motion during various activities, researchers found that an increased speed Amount of Knee Flexion During Stance of movement requires a greater range of motion in thc tibiol'cl11oral joint (Holdcn et aI., 1997; Pcrry ct I Phase of Walking and Running aI., 1977). As the pace accelerates from walking Range in Amount of Knee Flexio slowly to running. progressively more knee flexion is nccdcd during thc stancc phasc (Table 7\u00b72), Activity During Stance Phase (Degrees) SURFACE JOINT MOTION W(llking 0-6 Slow 6-12 SUrract~ joint motion. which is the Illation between Free 12-18 the articulating surfaces of a joint. can be described Fast 18-30 1'01' any joint in any plane with the lise of stcrcopho- Running Logrammetric mcthods (Sclvik, 1978, 1983)~ Bc~ Data itom Perry ct al. (1977). Range for seven subjects.","the instant center [() the contact point. A second line simultaneously but is considerably less in the tra drawn at right angles to this line indicates the di- verse and frontal planes. Surface motion in reclion of displacement of the contact points. The patellofcmoraljoint takes place in two planes sim direction of displacement of these points through- tancoLisly, the frontal and transverse, but is out the range of motion describes the surface mo- greater in the frontal plane. tion in the joint. In most joints, the instant centers lie at a distance from the joint surface, and the line Tibiofemoral Joint indicating the direction of c1isplaccrncnt o!\\\" the con- wct points is tangential to the load-bearing surface, An example will illustrate the lise of the instant c demonstrating thm one joint surFace is gliding on ter tcchniquc to describe the surface motion of the other (load-bcaring) surface. In the casc in tibiofemoraljoint in the sagittal plane. To determ which the instant center is found on the sudace. the the pathway of the instant center of this joint dur joint has a rolling motion and there is no gliding flexion, a lateral roentgenogram is taken of the k function. Because the instant center technique al- in full extension and successive films arc Laken lows a description of motion in one plane only, it is 10\u00b0 intervals of increased nexion. Care is taken not useful for describing the surface joint motion if kcep the tibia parallel to the ,-ray table and to p more than I5\u00b0 of motion takes place in any plane vent rotation about the femur. \\\\Vhcn a patient other than the one being rneasured. limited knee motion, the knee is Ilc,ed or e'tend only as far as the patient can tolerate. In the knee, surface joint motion occurs between the tibial and fcmoral condyles and between the Two points on the femur that arc easily iden fcmoral condylcs and the patella. In thc tibiofemoral ned on all roentgenograms are selecled and des joint, surface motion takes place in all three planes Locating the instant center. A, Two easily identifiable points on the femur are designated on a roentgenogram of a knee flexed 80\u00b0. B. This roentgenogram is compared with a roentgenogram of the knee flexed 90\u00b0, on which the same two points have been indi~ cated. The images of the tibiae are superimposed, and lines are drawn connecting each set of points. The perpendicular bisectors of these two lines are then drawn. The point at which these perpendicular bisectors intersect is the instant center of the tibiofemoral joint . for the motion between 80 and 90\u00b0 of flexion. Courtesy of Ian Goldie, M.D. Univ~rsity of Gothenburg, Gothenburg, Sweden.","natcd on each roentgenogram (Fig. 7.4..4). The Semicircular instant center pathway for the tibiofemor films are then compared in pairs, with the images of the tibiae supcl-imposed on each othcl: joint in a 19-year-old man with a normal knee. Roentgenograms with marked differences in tibial alignrncnt arc not used. Lines are drawn between tel' pathway for one subject, a 35-~\\\"ear-old m the points on thc felllur in the two positions, and with a bucket-handle derangement. is shown the perpendicular bisectors of these lines arc then Figure 7-7. drawn. The point at which these perpendicular bi- sectors intersect is the instant center or the If the knee is extended and Hexed aboul an tibiofemoral joint for each 10\u00b0 interval of motion normal instant center pathway, the libiofem (Fig. 7-4B). The instant center pathway throughout joint surfaces do not glide tangentially throu out the range of motion but become cither the entire range or knee Oexion and extension can tracted or compressed (Fig. 7-8). Such a kne annlogous to a door with a bent hinge that then be ploued. In a normal knee, the instant cen- longer fits into the door jarnb. If the knee is c ter pathway for the tibiofemoral joint is semicircu- tinually forced to move about a displaced ins lar (Fig. 7-5). center, a gradual adjustment to the situation be reflected either b~: stretching of the ligam After the instant center padnvay has been de- and other supporting soft tissues or by the im termined for the tibiofemoral joint. the surface sition of abnormall~' high pressure on the art motion can be described. On each set of superim- lar surfaces. posed roent-gcnograms the point of contact of the tibiorcmoral joint surfaces (the narrowest point in Internal derangements of the libiofcmoralj the joint space) is determined and a line is drawn may interfere with the so-called screw-h connecting this point with the instanl centet: A mechanism, which is external rotation during second line drawn at right angles to this line incli- tension of the tibia (Fig. 7-9). The tibiofem cates the direction of displacement of the contact ~ioint is not a simple hinge joint; il has a spiral points. In a normal knee, lhis line is tangential to helicoid, motion. The spiral motion or the t the surFace of the tibia for each interval of motion about the femur during flexion and extension from full extension to full flexion, demonstrating sults from the anatomical configuration of that the femur is gliding on the tibial condyles (Frankel et aI., 1971) (Fig. 7-6). During normal knee motion in the sagittal plane from full exten- sion to full flexion. the instant center pathway moves posteriody, forcing a combination of rolling and sliding to occur between the articular surface (Fig 7-6. A & B). The unique mechanism prevents the femur from rolling off the posterior aspect of the tibia plateau as the knee goes into in- creased flexion (Draganich et aI., 1987; Fu et aI., 1994; Kapandji, 1970). The mechanism that pre- vents this roll-off is the link formed between the tibial and Femoral attachment sites of the anterior and posterior cruciate ligaments and the osseous geometry of the femoral condyles (Fu el aI., 1994) (Fig. 7-6, B-D). Frankel and associates (1971) determined the in- stant center pathway and analyzed the surface mo- tion of the tibiofemoral joint from 90\u00b7 of Ilexion to Full extension in 25 normal knees; tangential glid- ing was noted in all cases. They also determined the instant center pathway for the tibioFemoral joint in 30 knees with internal derangement and found that, in all cases, the instant center was displaced from the normal position during some portion of the motion examined. The abnormal instant cen-","Gliding medial femoral condyle; in a normal knee, th A8 condyle is approximately 1.7 ern longer than th lateral condyle. As the tibia moves on the femu c from the fully flexed to the fully extended pos tion, it descends and then ascends the curves the n1edial femoral condyle and simultaneous rotates externally!. This motion is reversed as th tibia moves back into the fully flexed positio This screw-home mechanism (rotation around th longitudinal axis of the tibia) provides more st bility' to the knee in any position than would simple hinge configuration of the tibiofemor joint. Matsumoto et al. (2000) investigated the ax of tibia axial rotation and its change with kne flexion angle in 24 fresh-frozen normal knee ca daver specimens ranging in age From 22 to 6 years. The magnitude and location of the long tudinal axis of tibia rotation were measured 15\u00b0 increments between 0 and 90\u00b0 of knee fle ion. The magnitude of tibia rotation was 8\u00b0 at D _ 1I mIlI'------- I A. In a normal knee, a line drawn from the instant center of Abnormal instant center pathway for a 35-year-old man the tibiofemoral joint to the tibiofemoral contact point with a bucket-handle derangement. The instant center (line A) forms a right angle with a line tangential to the tib- jumps at full extension of the knee. Adapted from Frankel, ial surface (line B). The arrow indicates the direction of dis- VH., Burstein, A.H., &- Brooks, D.B. (1971). Biomechanics of in placement of the contact points. Line B is tangential to the ternal derangement of the knee, Parhomechanics as determin tibial surface, indicating that the femur glides on the tibial by analysis of the instant centers of motion. J Bone Joint Surg, condyles during the measured interval of motion. B. Pure 53A, 945. sliding of the femur on the tibia with knee extension. Note that the contact point of the tibia does not change as the femur slides over it. Eventually impingement would occur if all surface motion was restricted to sliding. Round points delineate contact points at the femur and triangles delin- eate contact points at the tibia. C. Pure rolling of the femur on the tibia with knee flexion. Note that both the tibia and the femoral contact points change as the femur rolls on the tibia. Also note that with moderate flexion, the femur will be~ gin to roll off the tibia if surface motion was restricted to rol- ling. D, Actual knee motion including both sliding and rolling.","of knee flexion. The tibial rotation increased ~-L'-JI Extension rapidly as the knee flexion angle increased and reached a ma:dmunl of 31 0 at 300 of knee flexion. '.\\\\',1 IL then decreased again with additional flexion (Fig 7-10). The location of the longitudinal rota- ... External tional axis was close to the insenion of the ante- rotalion during rior cruciate ligament (ACL) at 0\u00b0 of flexion. At extension continuous flexion up to 60\u00b0, the I'otational axis moved toward the insertion of the posterior cru- Screw\u00b7home mechanism of the tibiofemoral joint. D ciale ligament. Belween 60 and 90\u00b0 of flexion, knee extension. the tibia rotates externally. This mo the rotational axis moved anteriorly again (Fig reversed as the knee is flexed. A. Oblique view of t 7-11). This study showcd thaI lhc rolational axis mur and tibia. The shaded area indicates the tibial remains approximately in the area between the solid line axis for knee flexion and extension, dotte two cruciate ligaments. Any change of direction internal and external rotation axis of the tibia duri and tension of the cruciate ligaments and sur- ion and extension. AcJapred from Helier. A.J. (1974j. A rounding soft tissue may affect the movement and mechanics of movement of rite knee Joinr. In A. He and the 'location of the longitudinal tibia axis Disorders of the Knee fpp. i -17). Philadelphia.- J B. Lipp of rotation and thcrcby affccl joint load distri- bution. A clinical tcst. the Helfet test, is often useel to de- termine whether external rotation of the tibio- \u2022 Distraction Compression femoral joint takes place during knee eXl thereby indicating whether the screw-home m AB nism is illlact. This clinical tcst is performe the patient sitting with the kn~e and hip flex Surface motion in two tibiofemoral joints with displaced ancl the leg hanging free. The medial and instant centers. In both joints, the arrowed line at right an\u00b7 borders of the patella are marked on the ski gles to the line between the instant center and the tibial tuberosity and the midline of the pate tibiofemoral contact point indicates the direction of dis- then designated, and the alignment of the placement of the contact points. A. The small arrow indi- tuberosity with the patella is checked. In a n cates that with further fIeldon. the tibiofemoral joint will knee Hexed 90\u00b0, the tibial tuberosily aligns w be distracted. B, With increased flexion, this joint will be medial half or the patcll\\\" (Fig. 7-121\\\\). The k compressed. then extended fully and the movement of the tuberosity is obsel\\\\:cd. [n a normal knee. the tuberosity moves laterally during extensio \\\"Iigns with the latent! h\\\"lf or the patella at tension (Fig. 7-128). RotatOl')' motion in a n knee may be as great as hair the width patella. In a deranged knee, the tibia may not externally during extension. Because of the surface motion in such a knee, the tibiof joint will be abnormally compressed if the k forced into extension, and the joint surfaces m d.amaged.","patellofemoral Joint .......... ............. Tibia Plateau The surface motion of the patellofcmoral joint in Lateral ..\\\" ' .. the frontal plane may also be described by means or the instant center technique. This joint is shown to \u2022ACL have a gliding motion (Fig. 7-13). From full exten- sion to full flexion of the knee, the patella glides 0\u00b7'0 caudally! approximately 7 em on the femoral condyles. Both the medial and lateral facets of the \\\\. 5' femur articulate with the patella from Full exten- sion to 140' of flexion (Helme, 1990) (Fig. 7-14). Be- 6t?~L,.'. ::..... 30 .\u2022 \u2022\u2022\u2022\u2022\u2022\u2022\u2022 yond 90' of flexion, the patella rotates externally, .. .. .. .'. \\\". \u2022\u2022\u2022\u2022\u2022\u2022\u2022\u2022 45\\\" :md only the medial femoral facet articulates with the patella (Fig. 7-14B). At full flexion, the patella Fibula o Axis locallon an sinks into the intercondylar groove (Goodfellow et aI., 1976). The contact area of the lateral facet joint standard deviat of the patella is larger than the medial contact ar- eas and ranges from 0.5 to 2.5 cn1~ and less than 0.5 location of the axis of tibia axial rotation. The location to 2 em\\\"' ) respectively\\\" Contact areas increase \\\\vith the axis was close to the tibial insertion of the anterior an increased amount of flexion of the knee joint cruciate ligament (ACL) at A\\\" of flexion and gradually and increased pulling force of the quadriceps mus- moved toward that of the posterior cruciate ligament a cle (I-lehne, 1990). 45 and 90\\\" of knee flexion. The axis then moved anteri again and was approximately at equal distance from th .\u00a7 30 -- -r two insertions of the cruciate ligaments at 90\\\" of knee ro flexion. ACL, insertion of the anterior cruciate ligament a-0: - -r -- -- PCl, tibial insertion of the posterior cruciate ligament. \u00b7rxo 20 Reprinted v'\/ith permission from MatsurnolO, H., Seedhom, B 15 r-~ Sue\/a. Y, et \u00a311. (2000). Axis of tibial rotation and its change 'r\\\"o flexion angle. Clin Orthop, 371, J78-182. - -r-~ :0 -- Kinetics i= .30 45 60 75 90 Kinetics involves both static and d,vnamic ana ro 10 sis of the forces and moments acting on a jo >-0- Knee Flexion Angle Statics is the stud~\/ of the forces and moments a ing on a body in equilibrium (a body' at rest !o -o moving at a constant speed). For a bod)' to be equilibrium. two equilibrium conditions must IL met: force (translator:v) equilibrium, in which sum of the forces is zero, and moment (rotato jIBm'------- equilibrium, in which the sum of the moment zero. Dynamics is the study of the moments a The total tibial axial rotation (y-axis) plotted against the forces acting on a body in motion (an accelerat magnitude of knee flexion (x-axis) in fresh-frozen speci- or decelerating body), In this case, .the forces mens tested under unloaded axial conditions, The magni- not add up to zero, and the body displaces and tude of tibial rotation was below 9\\\" at A\\\" of knee flexion. the moments do not add up to zero and the bo Maximum rotation (31.]0) was measured between 30 to 45\\\" of knee flexion. Reprinted with permission from Matsumoto, H., Seedhom, B.B., Suda, Y, et al. (2000), Axis of tibial rotation and its change vi\/ith flexion angle. Clin Orlhop, 371, 778-182.","Knee flexed 90c Knee lully extended Helfet test. A, In a normal knee flexed 90\u00b0, the tibial tuberosity aligns with the medial half of the patella. B, When the knee is fUlly extended. the tibial tuberosity aligns with the lat\u00b7 eral half of the patella . \u2022 After the instant center (lQ is determined for the patellofemoral joint for the~ motion from 75 to 90\u00b0 of knee flexion, a line is drawn from the instant center to the con\u00b7 tact point (CP) between the patella and the femoral condyle. A line drawn at right angles to this line is tangen- tial to the surface of the patella, indicating gliding . \u2022","Superior Lateral M Lateral Medial ~.,~ - - - -30'-90\\\" I I (U '\\\\ Inferior 20' 45' 90' ---120\\\" ,Superior Lateral Me IA I Inferior i R ' m;0.. 135' B A, The position of the patella at different ranges of knee Functional anatomy of the patellofemaral joint. J 80ne Joint 58B. 287; and from Helme. H.I (1990). Biomechanics of the flexion motion. a, Contact areas during different degrees of parellofemoral joint and its clinical relevance. Clin Onhop. 25 73-85, flexion. Beyond 900 of flexion, the patella rotates slightly outwards. Adapted from GoodfelJo'J'l, I. Hvngerford, D.5., & lin\u00b7 \u2022I del, M (1976), PateJlofemoral joint mechanics and pathology. I. rotates around an axis perpendicular to the plane In this and subsequent chapters. the discussi of the fOl'ces producing the moments. Kinetic stalics and dynamics of the joints of the skelela analysis allows one to determine the magnitude of tem concerns the magnitude of the forces and the moments and forces on a joint produced by ments acting to move a joint about an axis body weight, muscle action, soft tissue resistance, maintain its position. It does not lake into acc and externally applied loads in any situation, ei- Ihe deforming effect of Ihese forces and mom ther static or dynamic, and to identify those situ- on the joint structures. This effect is indeed pre ations that produce excessively high moments or but the discussion is not within the s~ope of this forces.","STATICS OF THE TIBIOFEMORAL JOINT distinct from the rest of the bod.\\\". <'lIlt! a diagram o this free-bod.\\\" in tilt..' stair-climbing situation is Static analysis may be lIsed to determine the forces drawn (Calculation Bo,,,; 7-1). I\\\":'nlrn all rorces acting and moments acling on a joint when no motion on thl..: I\\\"rct..\u00b7\u00b7body. the three main coplanal- I\\\"o('(,:(:s an takes place or at one instant in time during a dy- idenlified a~ the ground rL'action force (equal to namic activity such n5 walking, running, or lifting body weight I), the tensile force through the patella an objecl. 1t can be performed for any joint in any tcndon exel\\\"ted h.v llw quadriceps Illust..:ll' , and th\\\\. position and under any loading configuration. In joint reaction force on the tibial plateau. The ground such analyses, eHher graphic or mathematical n.:action force (\\\\rV) has a known m<'lgnitude (L'qu;;llto methods may be lIsed to solve for the unknown body wt..'iglu). S~IlS('. line or <'lpplicalion. and poinl o forces or moments. application (poii'll or contact between the foot and A complete static analysis involving all moments and all forces imposed on a joint in three dimensions the ground). The palellnr tendol1 force (P) has a is complicated. For this reason. a simplified tech- known SC'IlSL' (awa.'; from the knee joint), lint..' of ap nique is oflen lIsed. The technique utilizes a frec- body diagrarn and limits the analysis lo one plane, to oplicaliun (along lhe patellar t('ndon). and point the three main coplanar forces acting on the frcc- body. and ro the main moments ~cting about the application (point or insertion of thc patellar tendol joint under consideration. The minimum magni- tudes of the forces and moments arc obtained. on till' tibial tulx.\u00b7rosit.\\\"), but an unknown l1lagni tude. The joint n:action force (J) has a known poilU When the simplified Free-body technique is used of application OJl the slIrl\\\"acL' or the tibia (the COJ1lac to analyze coplanar forces, one portion of the body point of tilL' joint surfaces betw(.'en the tibial and is considered as distinct rrom the entire bod.\\\\', and femora! cond,vlc:s, estimated from a roelllgenogram all forces acting on this free-body arc identified. A or the joint in the pn)!x~r loading configuration), bu diagram is drawn of the free-body in the loading sit- an unknown magnitude, sense. and line of applica uation (0 be analyzed. The three principal coplanar tion. Using \\\\'L'ctors cakuh\\\\lions <:\\\\11('\\\\ triangles law forces acting on the free-body are identified and the joint rL'action force (.1) and thl' pall.'lIar tendon designaLcd on the free-body diagram. force (P) call be c,dculated (Calcul\\\"tion Bo\\\\ 7-1) These forces afC designated as vectors if four It call bt..\u00b7 seen thaI the main musck forct..' has characteristics are kno\\\\vn: magnitude, sense. line of llluch gre<.ltL'1' inlhICIll:L' on the magnitude of\\\" th application, and point of application. (The tcrm '\\\"di- rection\\\" includes line of application and sense.) If -.joint reaction force than dot..\u00b7s the ~round !\\\"(.'actio the points of application for allthrec forces and thc directions for two forces arc kno\\\\vn, all remaining force produced b.\\\" bod~\u00b7 \\\\vcight. Note lhat, in this ex characteristics can be obtained for a force equilib- amplc (Calculation Box 7\u00b71), only til(' minimum rium situation. \\\\Vhen the free-body is in equilib- magnitude of the joint rt..'~lction force has been rium, the three pl-incipal coplanar forces are con- calculated. If other muscle I\\\"oret-'s arc considered current; that is. they intersect at a common point. In such as tht..' foret..' produced b~' tht..' contraction of th other words, these forces form a closed system with halllslring Inusc!es in stabilizing the knee, the jClin no resultant (i.e., their vector sum is zero). For this reaction force inCl\u00b7cast..\u00b7s_ reason. the line of application for one force can be determined if the lines of application for the other Th\\\\.' ne:'.;t Slt.\u00b7p in the static analysis is ~\\\\I1;:d.\\\"sis o two forces arc known. Once the lines of application the moments acting around the centcI- of motion 0 for all IIwee forces are known, a triangle of forces the libiofcrnoral joint with the knee in the same po can be constructed and the magnitudes of all three forces can be scaled from this triangle. sition and lht..' loading. configuralion shown in Ca culation Bo:'.; Figure 7\u00b71-1. The 1ll01llL'11I <'lIlal.\\\\\u00b7sis i An example will illustrate the application of the Llsed to cstimak' the minimulll ll1agnitudL' of th mOIl1L'nt produced through the patellar h:ndon simplified Ii'ee-body techniquc for coplanar forccs to the knee, In this case, the technique is lIsed to esti- which counterbalances the 1l10ll1Cnt on the lowcr le mate the minimum magnitude of the joint reaction produced b.'; the weight or the hod.\\\" as the subjec force acting on the tibiorcmoral joint of the weight- ascends stairs (Calculation Box 7\u00b72). bearing leg when the other leg is lifted during stair climbing. The lower leg is considered as a free-body. lin lhi:, C:lSl', the ground I\\\"l'~ll\\\"lillll rurn' is ;u.::lu;t1ly L'qllallo hod \\\\\\\\\\\"L'idlt mintl:- (he \\\\\\\\\\\"..::i!..:hl of till' IO\\\\\\\\\\\"L'r k\u00b7t:. BL'l\\\";III:-l' tit...\u00b7 \\\\widll o i(the 'it'Hwr k~ is lllillilT~;ll {1L'SS (hall Olli.' 1:'l1(h or Ihl' bOtl\\\\-), CI l.k' di,.. rl\u00b7~aranl. ;llld the li~url' for tlll:tl hod\\\\- \\\\\\\\\\\"l'i!.!hl l\\\\\\\\\u00b7U bl' tu lizL'd ill Illl' l\u00b7akul:lIion. . .-","~ !, Free-Body Diagram of the Knee Joint Force P .~.,... Force J The three main coplanar forces acting on the lower leg: \\\\.\\\\ Ground reaction iorce (W). patellar tendon force (P), and joint ;':.<\\\" Known: Point of applicalion reaction force (J) afe designaled on a free-body diagram of th I ,..\\\\Q,'Known: lower leg while climbing stairs (Calculation Box Fig 7-1\u00b71), Sense UnknO'.\u00b7',n: Magnitude Because the 100\\\\'cr leg is in equilibriulll, the lines of applicatio \u2022~ \\\\ Sense for all three forces intersect at one point. Because the linesof Line of application application for [I,.VO forces (Wand P) are known, the line of a plication for the third force (;) can be determined. The lines o Line of application \\\\\\\\ application for forces Wand P are extended until they jnter~ sect. The line or application for J Gill then be drawn from its Point of application .,\u2022..,-..__ ....\\\\ point of application on the tibial surface through the intersec Unknown: Magnitude \\\". -'. \\\\. tion point (Calculation Box Fig. 7-1-2). <\\\\.',-.\\\\ I '. \\\\ \\\"- :i~ \u00b7I o:__~\/~\\\\ J I---==~~--r\\\"'\/i'Known: Force W Magnilude Sense Line of application !Point of application \\\" ..' Force J v~ .:.~ \\\"'i l~~:T\\\\ibialemoral Force P \\\\ ( \\\\ ..... i contact point .\\\\~,, \\\\.'.'. , \\\\\\\\........ '. \\\\ \\\\:;.... \\\\ Intersection ~\\\\ pOint~ I -----\u00b7-\u00b7-~\u00b7=::::\u00b7:\\\"~~W-1J.-\u00b7'\\\"\\\"'---~---- I \\\\ ,,, ,,'., .'.'.'.'. Force P Now that the line of application for J has been determined, it 3.2W is possible (0 constru([ a triangle of forces (Calculation Box F Force J . . .J,,,,,.... \\\\, 7-1 ~3). First, a ve([or representing W is drawn. Next. P is 4.1W '.'.'.'.'. drawn from the head of ve([or W. Then, to close the triangle Force W _{, . force J is drawn from rhe head of vector W. The point at whic forces P and J intersect defines the length of these vectors. Now that the length of all three vectors is known, the magni tude of forces P and J can be scaled from force W, which is equal to body weight. It is determining the number of limes the length of force W can be aligned along the' force P and J, respectively. In this case, force P is 3.2 times body weight, and force J is 4.1 times body weight.","Free-Body Diagram of the Lower Leg During Stair Climbing The two main mornents acting around tt1e center of motion the tibioiemoral JOlfH (solid dOl) are designated on the free ( body diagram of the lower leg during stair climbing (Calcul \\\\ tion Box Fig. 7-2-1). \\\\ \\\\\/\\\\ The fleXing moment on the lower leg is the product of t \\\\ Force P \\\\ weIght of the body:- (W, the ground reaction force) and its :::M = 0 fever arm (a), 'Nhich is the perpendicular distance of the for W>:a=Pxb W to the center 0; motion aT the tibiofemoral joint. The co p =W xa terbalanCIng extending moment IS the product of the quad b ceps muscle force through the patellar tendon (P) and its le arm (b), Because tile lo\\\"\\\"er leg is in equilibrium. the sum of these two moments must equal zero (~M = 0). In this example. the counterclockwise moment is arbitrari designated as positive (W x a - P ~< b = 0). Values for lever arms a and b can be measured from anatomical specimens o on soft tissue imaging or fluoroscopy (Kellis & Baltzopoulos. 1999; Wretenberg et aI., 1996), and the magnitude of W ca be determined from the body weigt1t of the individual. The magnitude of P can then bE' found from the moment equilib num equation: W;.: a p~_.- b !Again the welghl of the lower leg IS disregarded because it is lESS ,han Oile \\\\Cntil of body vveight I Calculation Box Figure 7-2-1. e ------..- - - - - DYNAMICS OF THE TIBIOFEMORAL JOINT analysis must be taken into account: the acc tion of the body part under consideration an Although estimations of the magnitude of the mass moment of inertia of the body part. (The forces and moments imposed on a joint in static moment of inertia is the unit used to expres situations are llseful. most of Ollr activities are of a amount of torque needed to accelerate a bod dynamic nature. Analysis of the forces and mo- depends on the shape of the body.) (For mo ments acting on a joint during motion requires the depth studies of dynamics, sec Ozkaya & No use of a different technique for solving dynam,ic 1999.) problems. The steps for calculating the minimum m As in static analysis, the main forces considered tudes of the forces acting on a joint at a particu in dynamic analysis arc those produced by body stant in time during a dynamic aClivity arc as fo weight, muscles, other soft tissues, and externally applied loads. Friction forces arc negligible in a nor- I. The anatomical structures arc identified: mal joint and thus not considered here. In dynamic nitions of structures. anatomical landma analysis. two factors in addition to those in static point of contact of articular surface. and","4\\\\rl11s involved in the production of forces for Th..: torque is not only a product or the mass the biol11cchanical analyses. ment of inertia and the angular acceleration o 2. The angular acceleration or the moving body body part but also a product or the main Ill part is determined. force accelerating the body part and the perpe 3. The mass monlent of inenia of the moving ular distance of the force from the center of m bod~\\\" part is determined. of the joint (level' arm). Thus. 4. The torque (moment) acting abollt the joint is calculated. T = Fe! 5. The magnitude of the main muscle force ac- celerating the body pan is calculated. where 6. The magnitude of the joint reaction force at a particular instant in time is calculated by sta- F is the force expressed in newtons (N) tic analysis. d is the perpendicular distance expressed in m leI'S (01). :f In the first step, the structures of the body in- Because T is known and d can be measure volved in producing forces on the joint are identi- the body part from the line of application o fied. These are the moving body part and the main force to the center of motion of the joint, the e muscles in that body part that arc involved in the tion can be solved fOl\\\" F. vVhcn F has been c production of the motion. Great care must be taken lated, the remaining problem can be solved l in applying this first step. For example, the lever static problem lIsing the simplified free-body arms for all rnajor knee muscles change according nique to determine the l11inirnum magnitude o to the degree of knee Ilexion and gender (\\\\Vreten- joint reaction force acting on the joint at a ce berg et aI., 1996). instant in time. In joints of the extremities. acceleration of the A classic example will illustrate the usc o body part involves a change in joint angle. To narnic analysis in calculating the joint reaction determine this angular acceleration of the moving on the libiofemoral joint at a particular in body part, the entire movement of the body part during a dynamic activity (c.g., kicking a foo (Frankel & Burstein, 1970). A stroboscopic fi is recorded photographically. Recording can be done with a stroboscopic light and movie camera. the knee and lower leg was taken, and the an with video photogrummetry, with Selspot systems, acceleration was found \u00a30 be maximal at the in with stereophotogrammctry, or with other methods the foot struck the ball: the lower leg was almos (Gardner et aI., 1994; Ramsey & Wretenberg, 1999; tical at this instant. From the film. the maxima \\\\Vintel~ 1990). The maximal angular acceleration for gular acceleration was computed to be 453 ! a particular motion is calculated. From anthropometric data tables (Drillis e 1964), the mass momenl of inertia for the lo\\\\v Next, the mass moment of inertia for the moving was determined to be 0.35 Nm sec~. The to body part is determined. Anthropometric data on about the tibiofemoral joint was calculated ac the body parl can be used for this determination. ing to the equation; torque equals mass mome As calculating these data is a complicated pro- inertia times angular acceleration (T = (0), cedure, tables are commonly used (Drillis et aI., 1964). 0.35 Nm sec' x 453 rlsec' = 158.5 Nm The torque about the joint can now be calculated After the torque had been determined to be using Newton's second law of motion, which stales Nm and the perpendicular distance fran) the that when motion is angulat~ the torque is a product ject's patellar tendon to the instant center fo of the mass moment of inenia of the body part and tibiofemoraljoint had been found to be 0.05 m muscle force aCling on the joint through the pa the angular acceleration of that part: T = Ie< , tendon was calculated using the equation to where equals force times distance (1' = Fd), T is the torque expressed in newton meters (Nm) 158.5 Nm = F x 0.05 m I is the mass Illoment of inertia expressed in F.= -1=058.-0.-55=Nm-m- newton meters x seconds squared ( m sec~) F = 3170 N a is the angular acceleration expressed in radians per second squared (rlsec'). , 'i; : .. , .'\\\"","Thus, 3,170 N was the maximal force exerted by late s(;Jncc phase just before loe-ofr. This the quadriceps muscle during the kicking motion. ranged from two to four times body weight. v among the subjects tesled, and was <:Issociatcd Static analysis can now bt: performed to deter- contraction of the gastrocnemius muscle. In th mine the minimum magnitude of the joint reaction swing phase, contraction of the hamstring m force 011 the tibiofcrnoraI joint. The main forces on resulted in a joint reaction force approxim this joint arc id':lltificd as the patellar tendon force equal to bod)' weight. No significant dilTcrcnc found between the joint reaction force magn en,(P). Ihe gravilaliomtl force of Ihe lower leg and for men ancl women when the values were no izcd by dividing them by body weight. the joint reaction force (J). P and T arc known vec- tors. J has an unknown magnitude. sense, and line Andriacchi & Sirickiand (1985) sludied Ihe n of application. The free-body technique for three moment patterns around the knee joint during coplanar forces is L1sed to solve for J, which is found walking for 29 healthy volunteers (15 women a 10 be only slighrly lower Ihan P. men wilh an average age of 39 years). Figure depicts the flexion-extension, abduction~addu As is evident from the calculations, the two main and internal-external moments during the s factors that influence the magnitude of the forces on and swing phase of level walking. The momen a joint in d)'namic situations are the acceleration of normalized (0 the individual's body weigh the body part and its mass moment of inertia. An in- height and are presented as a percentage. The f crease in angular acceleration of the body part will produce a proportional increase in the torque about 4 the joint. Although in the body the mass moment of inertia is anatomically set, it can be manipulated ex- en tenl~l)Jy. For example. it is incrc.:ascd whcn a weight boot is applied (0 the foot during rehabilitative ex- I ercises of the extensor muscles 01\\\" the knee. Nor- mally, a joint reaction force of approximately 50\u00b0;(; 3 of body weight resulls when the knee is slowly (with no acceleration forces) extended from 90\u00b0 of flexion .ecn to full extension. In a person weighing 70 kg, this 'Q; force is approximately 350 N. If a IO-kg weight boot is placed on the foot, it will exert a gravitational ~ force or 100 N. This will increase Ihe joint reaclion force by 1,000 N, making this force aimosl rour 'C'\\\" times greater than it would be without the bool. e0 2 fl Dynamic analysis has been L1sed to investigate ~ the peak magnitudes of the joint reaction forces, ~ muscle forces, and ligament forces on the tibio~ .\/\\\\ ,\/\\\\u0. femoral joint during walking. Morrison (1970) cal- . ' \/-..., l \\\\ culated the magnitude of the joint reaction force \\\\\/ \\\\! \\\\ transmiucd through the tibial plateau in male and female subjects during level walking. He simultane~ V.,.' ' ' 1'\\\\ ' ., . .,-. ously recorded muscle activity elcctromyographi~ o1~O:::O-c.._-'-'..J\u00b7~---~\\\"'6~O~--'-\\\"'------'~--:1 cally to determine which muscles produced the peak magnitudes of this force on the tibial plateau Percentage of cycle during various stages of the gait cycle (Fig. 7-15). HS =. Heel strike - Joint reaclion Just after heel strike, the joint reaction force TO =.: Toe-ofl ..... Hamslrings ranged from two to three times body weight and .- -- Quadriceps le \\\\vas associated with contraction of the Iwmstring -- .. Gastrocnemiu muscles, which have a decelerating and stabilizing effect on the knee. During knee llexion in the begin- Joint reaction forces expressed as body weight trans ning of the stance phase. the joint reaction force through the tibial plateau during walking. one gait waS approximately lWO rimes body weight and was (12 subjects). The muscle forces producing the peak associated with the contraction of the quadriceps tudes of this force are also designated .. Adapted from muscle, which acts 10 prevent buckling of the knee. Morrison, lB. (1970). The mechanics of the knee joinr in The peak joint reaction force occUlTed during the rion lO normal w<lfking. J Biomech, 3, 51. \u2022 .. '!'\u00b7","extension moments during the stance phnse are ap- proximately 20 to 30 tilTICS larger than the moment produced in the frontal (abduction-adduction) and transverse (intcrnal-extcl-nal) planes. An increase in knee joint flexion-extension mo- A_ Flexion-Exlension ment amplitude has been reported at increased walking speeds (Andriacchi & Strickland. 1985; Moment Pallerns (Exlernal) Holden et aL. 1997). An increase in the production It Pattern 1 of adduction knee joint moment during stair climb- ing compared with level walking was reported b.\\\\' Yu 3.0 I et al. (1997). \u00a5>~ 'xac 2.0 I During the gait cycle, the joint reaction force ;!: uID:: 1.0 I shifts from the medial to the lateral tibial plateau. In the stance phase, when the force I'caches its peak r\\\"L' 0 I value, it is sustained mainly by the medial plateau .,0s '0ac0 1.0 I (adduction moment); in the swing phase, when the c 2.0 I '\\\" '\\\"IcD wX 3.0 I i. force is 111inimal. it is sustained primarily by the lat\u00b7 '\\\" - Stance --l-Swing-- eral plateau, The contact area of the medial tibial B. Abduction-Adduction plateau is approximately 50% larger than that of the lateral tibial plmeau (Keuclkamp & Jacobs, 1972). Moment Patterns (External) Also, the cartilage on this plateau is approximately I 1.0 three times thicker than that on the lateral plateau. x 0 The larger surface area and the greater thickness of the medial plateau allow it to more easily sustain ;!: 1.0 the higher Forces imposed on it. \\\"',~ 2.0 c 3.0 In a normal knee, joint reaction forces are sus- .~ .2 4.0 tained by the menisci as well as by the articular car- a 13 5.0 tilage. The function of the menisci was investigated 0 by Seed hom and coworkers (1974), who examined C. the distdbution of stresses in knees of human au- \u00abID \\\"0 topsy subjects with and without menisci. Their re- sults suggest that in load-bearing situations, the ID \\\"0 C '\\\" Internal-External Rotational Momenl Patterns (External) magnitude of the stresses on the tibiofemoral joint \\\"I \\\" ;;; 1.0 when the menisci have been removed may be as X ;c;; much as three times greater than when these struc- E 0.5 tures are intacL Fukuda et al. (2000) studied in vitro ;!: the load-compressive transmission of the knee joint I and the role of menbci and articular cartilage. The OJ load simulated was stalic and d).'namic impact load- 0.5 I ing. The testing was done in neutral. varus, and val- l, gus alignment of the knee joints in 40 fresh-frozen I c ;;; 1.0 ..- Stance - .. I'-Swing-\\\" ',0 ;c;; xID 'c\\\" w '\\\" pig knee speclmens. The compressive stress on the medial subchondral bone was lip to five times Flexion-extension (A), abduction-adduction (8), and higher with the menisci removed. This study points internal-external rotation (C) moments produced durin to the importance of the menisci as a structure to one gait cycle in normal subjects. The moments are no absorb load and protect the canilage and subchon- malized to each individual body weight X height and dral bone under dynamic conditions. pressed as a percentage. Reprinted with permission from In a normal human knee, stresses are distributed Andriacch( IP. &. Strickland. A.B. (1985). Gaie analysis as a over a wide area of lhe tibial plateau. If the menisci to assess joint kinetics. In N. Berme, A.E. Etlgin. O.A. Correis are removed. lhe stresses are no longer disll\\\"ibutcd et al. (Eds.). Biomech(lnics of Normal and Pathological Hum Over such a wide area but instead arc limited to a Articulating Joints. (NATO ASI series. Va\/93. 'pp. 83-I02)' contact area in the Center of lhe plaleau (Fig. 7-17). Orodrechr. Netherlands: Marr;nus Nijhoff. Thus, removal of' the menisci not only increases the","\u2022II I Force Force thought to carry lip to 70<}(; of the load across knee. ,Vlovcmcnt during knee Ilcxion of the meni l ...\\\\\\\\ III \\\\ ...~\u2022tttt would therefore protect the articulating surfa \\\\\\\\\\\\ Menisci removed while avoiding injury to it. III tIl Vedi et al. (1999) studied menisci movement in I young football players with normal knees w MRI. The knee flexion movement was scanned fr Normal full knee extension lo 90\u00b0 of knee flexion. The im ing technique allowed for both standing (weig Stress distribution in a normal knee and in a knee with the bearing) and sitting (non-weight-bearing) and w menisci removed, Removal of the menisci increases the performed simultancollsl~tin the sagittal and tra magnitude of stresses on the cartilage of the tibial plateau verse plane. Figure 7-18 shows the movements and changes the size and location of the tibiofemoral con\u00b7 the transverse plane of the medial and lateral me sci expressed in millimeters (mean) from full ext tact area. With the menisci intact, the contact area encom- sion to 90\u00b0 Ocxion of knee joint motion. Movem passes nearly the entire surface of the tibial plateau. With was significantly greater in weight-bearing than the menisci removed, the contact area is limited to the non-\\\\Veigllt~bearing for both lateral and med center of the tibial plateau. menisci. The contributions of the menisci art: lhe fore not only to protect the articular cartilage a magniwde of the stresses on the cartilage and sub- subchondral bone but also to contribute aClively chondral bone at the ceiller of the tibial pl~llcau but knee joint slabilit~:. also diminishes the size and changes the location or the contact area. Over the long term, th~ high STABILITY OF THE KNEE JOINT stresses placed on this smaller contact area may be harmful to the exposed cartilage, which is usually The key to a healthy knee joint is joint slability. T soft and fibrillated in that area. The menisci are osseous configuration, the menisci, the ligamen the cnpsulc, and the muscles surrounding the k joint produce joint slability (Fig. 7-1, A & B). If a 7.1 Ant 5.4 Ani 9.5 6.3 , 0 f 3.3r ,\\\"- Flexion I \\\\ I \\\\ 3.6 iN \\\\, \\\\ -J\u2022_- \\\"- -L., _- ,\\\"- . --, -4~.0- I 3.9 -4- ,\\\\ 3.8 ,\/ 90 , Medial menisci Post 5.6 Post B Medial Lateral Lateral menisci menisci menisci A Simplified diagrams showing the mean movements of the with permission (rom Vedl, V. WiJjiams. A., Tennant. S.J.. el aJ. medial and lateral menisci from full knee extension to 90\u00b0 (1999). Menisca! movemenr. An In-vivo srudy u~in9 dynamic M knee flexion during two conditions. A. Erect and weight~ Bone Join! Swg, 818(1), 37-41. bearing. B. Sitting, relaxed. and bearing no weight. Adapted","A.ACL Injury injuries. meniscal injuries. and possible cartilage degenera\u00b7 i. 30\u00b7year-old male suffered an external rotation trauma lion. In this case. the patient firs! completed a course of J;_ in his right knee while downhill skiing. Following the conservative treatment with physical therapy. After 6 ~~;,: trauma, he experienced sharp pain, progressive joint effu- months. the subjective inS(clbilily was present during SPOrts ,~,iqn,_and subjective instability. ,During careful examination and daily activities such as gail and stair climbing. To com\u00b7 Ii' ,by a specialist, an anterior positive drawer test was dlag- pensate for the ACL deficiency, the patient altered his gait patterns, presenting quadriceps avoidance gait to prevent <\\\";'n,osed, and the Lachman test and pivot shift test were the anterior translation of tl1e tibia when the quadriceps contracts at the midstance phase of the gait (Andriacchi & ': found positive. An MRI confirmed the ACL rupture (Case Birac, 1993: Berchuck et aI., 1990). j' Si~dy Fig 7-1-1) The patient went for surgical treatment. The MRI below -,. The rupture of the primary stabilizer of the knee joint (ACl) (Case Study Fig. 7-1-2) shows the ACL status after patella bone-tendon-bone autograft was performed 10 months leads to a progressive structural alteration of the knee. A pri- post-trauma. mary objective of the treatment is the prevention of fe-injury of the knee in the hope of preventing additional ligamentous Case Study Figure 7-1-1. Case Study Figure 7~1\u00b72. of these structures arc malfunctioning or disturbed, approximately 55% of the applied load at full ext knee joint instability will occur. The ligaments arc sion. The role of the lateral collateral ligament t.he primm)' stabilizer for anterior ancl posterior creases with joint flexion as the posterior structu translation, varus and valgus angulation, and inter- become lax. The 1l1edial collateral ligament (supe nal and external rotation of the knee joint (Case cial portion) is the primary restraint to valgus ( Study 7-1), duction) angulation and resists 500\/0 or the exter valgus load. The capsule. the anterior and poster F,; et aL (1994) sUlllmarized the functions of the cruciatc ligaments, share the remaining valgus lo Internal rotational laxity seen in the 20 to 40\u00b0 ran knee ligaments, The ACL is the predolllinant re- of knee nexion is restrained bv the medial collate straint to anterior tibial displacement. The ligament ligament and the ACL Finally, external rotation l accepts 75% or the anterior force at full extension ity seen in the 30 to 40\u00b0 range of knee flexion is and an additional 10% (up to 90\\\") of knee nexion, strained by the posterior cruciate ligaJllcnt at 90\u00b0 The posterior crudate ligament 1S the primary re- knee Ilexion, straint to posterior tibial translation: il slIstains 85 to 100% of the posterior force at both 30 and 90\\\" of In vivo measurement or the normal ACL has b knee flexion. The latera) collateral ligament is the performed by Beynnon et aL (1992), They place primary restraint to varus angulation and it resists","strain transducer arthroscopic'll)y in the ACL. The tendon and it contributes the least to the leng results showed that strain in the ACL was related to the quadriceps muscle force lever arm (app knee Oexion (with the most strain occurring ncar mately 10% of the total length). As the knee i full extension) and increased with quadriceps con- tended. the patella rises from the intercon traction. Less strain occurred with co~conlraclions groove, producing significant anterior displace of both the quadriceps and the hamstring muscle of thc tcndon. Thc length of thc quadriccps groups and at greater degrees of knee flexion. This lever arm rapidly increases with extension up to indicates that muscle contraction and co-contraction at which point the patella lengthens lhe lever contribute to the stabilitv of the knee joint bv in- by approximately 300\/0. crcasing thc stiffncss of the joint. Kwak et al. (2000) studied in vitro the effect of hamstrings and iliotib- With knee extension bc\\\"ond 45\u00b0, thc Icngth o lever arm is diminished slightly. \\\\,Vith this dec ial band forces on the kinematics of the knee. At var- in its lever arlll, the quadric.:cps muscle force ious knee Oexion angles, human knee specimens increase for the torquc about the knee to rcrnai were tested with different muscle-loading patterns. same. In an in vitro study of normal knees. Licb The quadriceps muscle force was always present, Perry (1968) showcd that thc quadriccps m and the test was performed with and withollt han)- force required to extend the knee (he last 15 string muscle force and with and without iliotibial creased by approximately 60% (Fig. 7-19). band force. \\\\AJith loading of simultaneous quach\u00b7i. eeps and hamstring muscle force. the tibia trans- If thc patella is removed from a knec, the I)a latcd posteriorly and rotatcd externally. The effecI tendon lies closer to the center of motion o \\\"\\\"\\\" similar for thc iliotibial band simulated forces tibiofemoral joint (Fig. 7\u00b720). Acting with a sh but thc cffcct was smallcr. lever arm, the quadriceps llluscle must pro even more force than is normnlly required for a Many in vitro studies suggest that the ham- tain torque about the knee to be maintained du strings are important anterior and rotational stab.i- lizers of the tibia. In vivo studies have shown that 75 co-contractions of the quadriceps and hamstring muscles arc highly present in normal knee joints and dail.'\\\", activities (Baratta et a1., 1988; Solomonow & D'Ambrosia, 1994). Thc co-contraction mcchanisms also increase the knee joint stability in vivo (Aagaard ct al .. 2000; Markholf et al .. 1978; Solomonow & D'Ambrosia, 1994). Howevel~ the complex mecha- nism in vivo of muscle activity as a knee stabilizer, the extent of protection, and the biomechanical and clinical imparlance needs futther research (Grabiner & Wcikcl', 1993). FUNCTION OF THE PATELLA o 90-60 60-30 30-15 The patella serves two important biomechanical Knee Motion (degrees) functions in the knee. First, it aids knee extension by producing anterior displacement of the quach-i- Flexion - - - - EXlension eel's tcndon throughollt the entire range of motion. thereby lengthening the lever arm of the quadriceps ~~------ muselc force. Second, it allows a wider distribution of compressive stress on the femlll- by incrensing the Quadriceps muscle force required during knee motio area of contact between the patellar tendon and the fcmur. The contribution of thc patella to the Icngth from 90\\\" of flexion to full extension. Adapted from L of the quadl\\\"iceps muscle force lever arm varies f1. & Perry, 1. (J 968). Quadriceps funccion. An dflacomica from fullllcxion 10 full extcnsion of thc knee (Lindahl mechanical study using dmplJtMed limbs. J Bone Joint Su & Movin, 1967; Smidt, 1973). At full Ilcxion, whcn 50A, 1535. the patella is in the intercondylar groove, it pro~ duces littlc anterior displacemcnt of the quadriccps , ,. \\\"\\\"','","~~===== knee is almost directly above the center of rotatio of tho patellofemoral joint. As knee Oexion i \\\"------------- - \\\\\\\\ --------- creases, the center of gravity shifts further awa \\\\ from the center of rotation. thcrcb.y greatly increa ~ - Instant center ing the Ilexion moments to be counterbalanced b the quadriceps musclc force. As the quadricep Normal muscle force rises. so docs the patellofemoral joi reaction force (Hungerford & Barry, 1979; Reilly -L=-- J\\\\>larlons, 1972). After Patellectomy Knee flexion also influences the patellofemor Quadriceps muscle lever arm (represented by the broken joint reaction force by affecting the angle betwee line) in a normal knee and in a knee in which the patella the patellar tendon force and the quadriceps te has been removed. The lever arm is the perpendicular dis- don force. The angle of these two force comp tance between the force exerted by the quadriceps muscle nents becolTlCs more acute with knee flexion, i through the patellar tendon and the instant center of the creasing the magnitude of the patellofemoral joi tibiofemoral joint for the last two degrees of extension. reaction force (Calculation Box 7-3). Reilly an The patellar tendon lies closer to the instant center in the Martens (1972) dctcrmincd the magnitude of th knee without a patella. Adapted from Kaufer. H. (1911). Me- patellofcmoral joint reaction force during sever chanical function of the parella. J Bone Join! Surg. 53A. 1551. dynarnic activities involving val\u00b7ying amounts knee flexion. During IC\\\\'e1 walking, which requir relatively little knee flexion, the reaction force w low. The pcak valuc. ill the middle of the stan phasc when flexion was greatest, was one-ha body weight. The joint reaction forcc was much greater durin activities that require greater flexion. During kn bends to 90'. this force reached 2.5 to 3 times bod wcight with the knee Oexed 90' (Fig. 7-21). Throug 13000 ...... Palellofemoral joinl reaction force the last 45\u00b0 of eXlen~ion. Full active extension of --- Quadriceps muscle force such a knee may require as much as 30% more quach'iceps force than is normally required (Kaufer. 2000J 1971). This increase in force may be beyond the ca- pacity of the quadriceps muscle in some patients, :s particularly those who have intra~articular disease or are advanced in age. !\\\"! 0 \\\"- 1000 STATICS AND DYNAMICS OF THE o 20 40 60 80 PATElLOFEMORAl JOINT Knee Flexion (degrees) During dynamic activities, the magnitude of the mus- cle forces acting on a joint directly affects the magni- Patellofemoral joint reaction force and quadriceps muscl tude of the joint reaction force. In general, the force during knee bend to 90\u00b0 (three subjects). Adapted greater the muscle forces, the greater the joint reac- lion force. from Reilly, D. T. g. Martens, M. (1972). Experim.ental analysis o In the patellofemoral joint. the quadriceps mus- the quadriceps muscle force and patello\/emaral joint reaction cle force increases with knee Oexion. During re~ force for various activities. Acta Orthop Scand. 43. 126 (axed upright standing, minimal quadriceps muscle forces are required to counterbalance the small nexion l1lornents about the patcllofemoral joint be- cause the center or gravity of the body above the","Joint Reaction Forces at the Knee in Flexion Knee flexion influences the patellofemoral joint reaction force by changing the angle between the patellar tendon and the quadriceps tendon (Calculation Box Fig. 7-3-1, A & B). The angle between the patellar tendon (P) and the quadriceps tendon (Q) is 35\u00b0 with the knee flexed 5\u00b0 (left top) and 80\u00b0 with the knee flexed 90\u00b0 (left bottom). Values for the ten- don angles are from Matthews and Associates (1977), who determined the angle roentgeno- graphically after placing two metal wires along each of these tendons. The pateJlofemoral joint reaelion force with the knee in 5 and 90\u00b0 of flexion is oblained by constructing a parallelogram of forces for each situation and using trigonometric calculations. The pateJlofemoral joint reaction force (J) is the resultant of the hvo equal force components through the patellar tendon (P) and the quadriceps tendon (Q). As the angle between these force components becomes more acute with greater knee flexion, the resultant joint reaction force (J) becomes larger. Adapted lrom Wikrorin Cv.H. & Nordin, M. (1986). Introduction to Problem Solving in Biomechanics (pp. 87-129). Philadelphia: Lea & Febiger. o ,,\/ p P------------\/,,'\\\" \/\/ Tibio femoral flexion 5\\\" 1000 N J ~ 601.409 J2 '\\\" Q2 .... p2 _~ 2PQ. cos 35~ J = )361695 J ~ 601.41 Io 1000 N !---J--\\\"\\\"-'r: 80\\\" I I I I I p I I I I 10;0 N ---------j\u00b7::-;285_61 I Tibio femoral flexion 90\\\" J2 ~~ Q2 -;.. p2 .~ 2PQ \u2022 cos 80~ J ~ 11652703 J ~ 1285_57 Calculation Box Figure 7\u00b73\u00b71A. Calculation Box Figure 7\u00b73-1B. - - - - - - - _ . _ - - - - --------_..._------_._--- --_._.--- -._------","'\\\" Extensor Mechanism Injury contact surface area increases in size somew (Goodfellow et aI., 1976). To some extent, this 30-year-old basketball player had a forceful knee flex- crease in the contact surface with knee nexion co ion while coming down from a jump. A strong eccen- pensates for the larger patellofemoral joint react force, 11' a tight iliotibial band is present, of the quadriceps produced abnormally high patcllofemoral joint force may shih laterally, ca \\\" ,0n\\\",lp loads in the patella, leading to a fracture at the infe- ing abnormal patellar kinen1atics and load-bear (Kwak et aI., 2000), In this case, the patella fracture occurred because forces of the quadriceps overcame the osseous The quadriceps muscle force and the tor around the patellofemoral joint can be extrem of the patella. The weakest link was the patella. high under certain circumstances, particula picture shows a fracture at the patella accompa- when the knee is flexed-for instance. whe f)ied by a significant fracture separation that resulted from basketball plaver suffers a patella fracture a the quadriceps traction force. result of indirect forces played by an eccen Because of the fracture. the extensor mechanism is un- contraction of the quadriceps (Case Study 7 =;'. able to function and extend the knee. It will directly affect Another extreme situation was observed durin Co; the stability of the pate!lofemoral joint and the distribu- stud~; of the external torque on the knee p tion of the compressive stresses on the femur. At the duced by weight lifting: one subject ruptured same time, the impaired function of the quadriceps de- patellar tendon when he lifted a barbell weigh creases the dynamic stability at the knee joint 175 kg (Zernicke et aI., 1977). At the instant (patellofemoral and tibioiemoral joints) that is necessary tendon rupture, the knee was flexed 90\u00b0; :J. for daily activities such as gait and stair climbing. torque on the knee joint was 550 Nm and quadriceps muscle force was appro:dt11a 10.330 N. Because of the high magnitude of quadric muscle force and joint reaction force during tivities requiring a large amount of knee flex patients with patcllofemoral joint deran ments experience increased pain when perfo ing these activities. An effective mechanism reducing these forces is to limit the amoun knee flexion. Summarv out knee bend, the patellofemoral joint reaction 1 The knee is a two-joint structure that is co force remained higher than the quadriceps Illuscle posed of the tibiofel11oral joint and the pate force. During stair climbing and descent, at the point femoral joint. when knee flexion reached a maximum of approxi- mately 600, the peak value equaled 3.3 times body ?:>: In the tibiofemoral joint, surface motion weight. curs in three planes simultaneously but is grea by far in the sagillal plane. In the patellofem When the knee is extended, the lower part of the joint, surface Illotion occurs simultaneously in patella rests against the femur. As the knee is flexed planes, the frontal and the ll-ansverse, and is gre to 90\u00b0, the contact surrace between the patella and in the frontal plane. femur shifts cranially in vivo and under weight- bearing conditions (Komistek et aI., 2000). The 3 The surface joint motion can be described w the use of an inslant center technique. vVhen formed on a non11al knee, the technique reveals following: the instant center for sllccessive inter of motion of the tibiofcmoral joint in the sagi plane follows a semicircular pathway, and the di tion 01\\\" displacement of the tibiofemoral con","points is tangential to the surface of the tibia, indi w Dra!!,\\\\nich. L.D .. Andriacchi, T.P.. & Andersson, G.B.J. (19 eating gliding throughollt the range o[ motion. I~nlcraction betwccn intrinsic knec mechanism and knee extensor mech'lllislll. ) OnhoJ} Res. 5, 539-547. The scrc\\\\v-homc mechanism of the tibio- femoral joint adds stability to the joint in full exten- Drillis, R., Conlini. R., & Bluestein, \\\\1. (1964). Bod~' segl sion. Additional passive stability' to the knee is given par'lmc[(\u00b7rs. A stln'ey of 1l1l..'<lStll\\\"elllent tec!miqut.'s. by the ligamentous structure and menisci and the Lil\/lbs, 8. 44. dynamic stability by' the muscles around the knee. Frankel. V.H. & Burstl'in, A.I-I. (19701. OnJlOptldic Bi S The tibiofemoral and patellofemoral joints are cfUlllics. Philadelphia: 1.t.'a &- Fcbigcr. subjected to great forces. Muscle forces have the Fr'Hlkel, V.H., Burstein, A.H., l\\\\c Brooks, D.B. (1971). Bi greatest influence on the magnitude of the joint rcw chanics of internal dl'rangeTw:nt of Lht.' knee. Patho action force, which can reach several times body chanics as dl'tcrmincd b.v an~d~'sis of the instant ccnte weight in both joints. Tn the patcllofcmoral joint, motion. J BOlle Joillt SlIrg. 53..\\\\, 945. knee flexion also affects the joint reaction force, with greater knee flexion resulting in a higher joint Fu, ElL Harner, CD., Johnsoll, D,I.., ct <11. (1994). Bi reaction force. chanics of the kncl' ligamenLs: Basic concl'pts and cli Although the tibial plateaus arc the main load- application. II\/Sfr COllrsi' Lt.'ell\/re, -t3, 137-148. bearing structures in the knee, the cartilage. Fukuda, 'I{., Takai. 5., Yoshino, N., et al. (2000). Impact menisci, and ligaments also bear loads. The menisci Lransmission of the kncc joint~infltlence of leg align aid in distribt~ting the stresses and reducing the and the role 01\\\" IllL'niscus and articular carlilage. Cli load imposed on the tibial plateaus. Bioll\/L'ch, 15, SI6-S2l. Gardner. T.R .. Ateshian, G.A .. Grclsarner, R.P., et al. (199 The patella aids knee extension by lengthening 6 DOF knec testing de\\\\'ice to d~termine patellar trac the lever arm of the quadriceps muscle force and patellofellloral joint contact area \\\\'ia stereo throughout the entire range of motion and allows lOQramrnl'trv. :Idl' Bio('II'.,; :IS.\\\\1E BED. 28, 279-280 a wider distribution of compressive stress on the Gr)(ldl\\\"dlow, .I.', llungcrl\\\"o'rd, D.S., & Zindd, \\\\1. (19 femur. Patl'llofenloral joillt llH.'chanics and paLhology. I. F REFERENCES tional ,uwtorn.v of the patellofL'lllO!';t1 joint. J Bonc Surg. 5813, 287. Aagaard. P., Simons~n, E.B., And~rsen, J.L., et a1. (2000). An- Grabine!', .\\\\-I.D. & Weiker, G.G. (1993). :\\\\ntl.'rior cruciate ment injury and hamstring CO-<lcli\\\\'ation. elillical tagonist mtlscl~ co-'lctiv<ltion during isokinetic extension. IIlt'ch, 8. 216-119. Grood, E.S. l\\\\: Suntav. \\\\V.J. (1983). A coordinate svstell Scali J J1ed Sci Sports, 10(2),58-67. clinical descriptio;l of three dimensional motion~ App tion to the knee. J Biollll!ch Ellg. 105, 136-144. Andriacchi,1. P. & Birac, D. (1993). Functionalligamellt tcst- He!llIL', 1-1.1. (1990). Biomechanics of lhc patellol\\\"emor.d and its clinical relevance. Cfill Orthop, 258, 73-85. Oinr~\\\"JliOnp the anterior cruciat~ l4i!~.0!-a4l7ll.~nt deficient knee. C!ill Hell\\\"eL, A..J. (1974). AnatolllY and mechanics of mO\\\\'ellle Rei Res, 288 the knec joint. In A. He]fct (Ed.), Disorders o(the Knc(' (Alarch), 1-171. Philadelphia: J.B. Lippincott. Holden, J.P., Chou. G.. &- Stanhope, S.J. (1997). Change Andriacchi, T.P., Kramer. G. ;'vl., & Landon, G. C. (1979). knee joinL function o\\\\\\\"er a \\\\~'ide range of walking spc Cfillica! Bio\/llL'ch,12(6L 375-382. Three-dimensional coordinate data processing in human Hungerford, D.S. &- BarT\\\\', ;\\\\:1. (1979). Biomechanics of patdlofelTloral joint. Cli,l OnhoJ!, Ic+c+, 9-1 S. motion analysis. J Biolllcch Eng, \/01, 279-283. Kapandji, l.A. (1970). Thc knl'c. In LA. Kapandjii (Ed.l. Physiology oFthe Joillts (Vol 2, pp. 72-135). Paris: Edi Andriacchi, T.P. & Strickland, A.8. (1985). Gait analysis as a \\\\1<1 loi ne. Kaul\\\"er, H. (1971). \\\\Iechanical function of tllt' patella . .l tool to assess joint kinetics. In N. Berme, A.E. Engin. Joill! Surg. 53A. ISS I. Kellis, E. & BHltzopCllJlUS, V. (1999). In \\\\'i\\\\'o delerminatio D.A. COl'reis, et al. (Eds.). Biollli'clulllics o{ Norll\/a! and the patella and Iwmstrings rnonh.'nt arms in adult m using videofilloroscopy during submHxinwl knee l':\\\\tl'n Pathological J1l111WII Articulating .loints (NATO ASI series, and flexion. Cfinical Biolliech. I -t, 118-124. Kcttelkamp, D.B\\\" Johnson, R.1., Smidt, G.L .. Chao, Vol 93, pp. 83-102). Drodrecht. Netherlands: :',\u00b7lartinus Walker, rv1. (1970). An c1ectrogoniomctric stud.\\\\\\\" of motion in normal gait. J BOlli': Joilll Sur.>;, 52:\\\\, liS. Nijhoff. Kettelkamp, D.B. &- Jacobs, A.\\\\V. (1972). Tibiofclllora! con area-dL'termination and implications. J BOIIL' Joil\/t S Baratta, R., Sololllonow, ivi., ZhOll, 8.1-1., Letson, D., 5-tA. 349. Komistek, R.D., Dennis, D.A., ;\\\\labe, J.A., d HI. UOOO). A Chuinard, R., D'Ambrosia, R. (1988). Muscular co-activa- vh'o determination of pHtellol\\\"ernora! c(ll1tact posit Cfillical Biol\/lcch, 15,29-36. tion: The role of the antagonist musculature in maintain- ing knee stability. Alii J Sports Alcd, 16, 113-122. Berchuck i\\\\'1., Andriacchi, TP., Bach, B.R.. Reider, B. (1990) Gait adapt ions by patients who h,\\\\\\\\'e a deficient anterior cruciate ligament. J BOlli' Joillt Surg. i2A, 871-877. Beynnon, 8., Howe, J.G., & Pope, rVI.H. (1992). The measure- ments of anterior cruciate ligament strain in vivo. lilt 01'- lhop, 16. 1-12.","Kroelller. K.I-I .. M;llTas. \\\\V.S ...\\\\1cGlothin. J.D .. 1..'1 al. (1990). Reilly, 0.1'. &. \\\"'Iancus. ,\\\\'1. (19i2). E.\\\\:pel'imclll;.'I1 ;Inalysis On the IlH.'ilsun:nh.'nts of human stn:ngth. 11111 Imll\/strial thl' qlwdriceps musclc force and patcllof\\\"moral joint rea rr\\\"OIUl111ic!I\u00b7. 6. 199-210. tion force for variolls 'lctivitic-s. :\\\\ew Orrhop Scalld. 4 Kwak~ 5.0.. ,\\\\hmad, C.S .. Gardner. T.R .. 1..'1 al. (2000). Ham\u00b7 126. Sirings and iliotihial forces affect knee ligamellts and con- tact palh:rn.l O,.,ltop ReS. IS, 101-IOS. Reulc;1ux. r. (1876). In The KillCl1lalio uf Jlachillc:ry: Outli LaTllorc;IU.\\\\:. L.. (1971). Kinematic IllC:lsurt:TllcnIS in Ihl.\u00b7 stlldy of II Theory of .'-1achillcs. London: ~l[lcmilIan. of hurn:tll w;:lIking. Biomcch;lnics Lah. Uni\\\\'t.'rsiIY of (;tli- forni:l, S'lll rr~ncisco. B\/\/II Prostlteth' Res, Sp1971, 10-15. Sccdhom. B.s.. Do\\\\\\\\'son, D., &. Wright. V. (19i4). The 10; L:ltlbenth;d. !\\\\..N .. Smidt, G.L., & !\\\\.ctLdkamp, D.B. (1971).\\\"\\\\ quantitative analysis of knee motion during activities of bl:'aring function of Ihl' menisci: r\\\\ prdiminary study. dail\\\\' living. I'II\\\\'S Til!!,., 52. 3-L 0.5. lngwl'rsl'n, ct :II. (Eds.), Thc h\/\/CC loill\/: f?en.'1\/t .' LC\\\\'I.\u00b7ns: '\\\\,S\\\"Yllll1l~lI1. V.T., & Blosser. J.'\\\\. (1948). Trans\\\\'crsc \\\\'(l\/ICC.~\u00b7 ill Basic Research (wd Clinica! .'lsp(~rlS (I'p. 37-4 rot;ltion of the seglll\\\"fHs of the lower cXlr('mity in locomo- tion, 1 BOlli! 10iut Sur.!..:. 30A. S59. r\\\\mS!l:rdam: Exccrpta Medica. Licb. FJ. ~ I)erry. J. (I968). Quadriceps function. An ;UHllOI1l- ical ;lnd mcch:lllical sludy using ;lIl1putaled limbs. 1 Bmw Seh'ik. G. (1978). Roentgcn slC'l'cophotogr.lllllllclry in Lun loil\/t Surg, 50~\\\\, 1535. orSweden. In .-\\\\.M. Coble!l'l. & R.E. j\u00b7Jl'lTon (Eds.), Applic LiIH.bhl, 0 . .& Mm\u00b7in,.-\\\\. (1967). TIJ(,' 1lH.'chanil':-; of l'xt...'nsion \/jolls flUlIltll1 Biosten:mJII..'lru:s. fIroe 81'\/\u00a3 (166) (p of the kncc joint. .\u00b7\\\\eta 01'1\/1011 Scaml, 38, 226. 184-189). ~;:;II'kholr. K., Gr:lff-R;l<lford, f\\\\., &. Amstul'I.. H. (19iS). In \\\\'i\\\\'O Sdvik, G. (1983). Roentgen stcrl.'ophotogramllleiry in 0 knce slllbility. 1 BOlli' 10ill\/ SlIl'g. 60.'1. 664-674. ~laISllmot(), 1-1.. Si..'i..'dholll, B.B.. Suda. Y., C\\\"t <:II. (2000). Axis of thop;:ledics. In R.E. HelTon (Ed.), BioslereOluetric:s 'S tibial rot.Hioll and its change with flcxion angle, C\/ill Or\u00b7 Pro\\\" SP\/E (36\/) (pp. li8-18S). . '),Op, 371. 178-182. Smidt. G.L. (1973). Biomechanical :-nnlysis of knee nexi ',\\\\l<1ltl1(:\\\\\\\\,s, L.S .. Sonstc:gard. D.A .. &. I-lenke, .I.A. (1977). Lond ;lUd c.\\\\:wnsioll_ 1 Bioll\/celt, 6. 79. h\\\"arillg characterislics of lhe palellofemor;d joint. ,\u00b7\\\\era Solomonow, M. &. D'r\\\\mbrosia. R. (1994). Nellr:!1 l'1'f1ex ;I Onhop S,\u00b7a\/\/(I. 48.311. ;tnd muscle control of knl'c sl;\\\\bilil~' :lIld motion. In W M'HTis('n.J.B. (1970). The mechanics of the kIWi..' joint in re- Scott (Ed.), The Knce (pp. 107-120). New York: Moshy. Vl'di, V., Williams, A\\\" Tennant, S.L ('I :II. (1999). Mcnisc lation [0 nonn:'l! walking. J Bicol\/cch. 3. 51. rnon::mcnt. An ill-vivo study llsing dynamic i\\\\-lRL J BO !'\\\\i1.P., Droughl, :\\\\.B .. !\\\\.ory. R.C. (1964). \\\\Valking 1':11- loim SlIrf:!.. 8IB(J), 37-41. Winll'l', D.A. (1990). In Bio!llee\/ullIics flud Motor CO\/ltrol ll'::l'nS of l1orl11:d men. 1 130111..' Joillt S!l!\u00b7.~, -I6A, 335. 1'11111\/1111 Be!wviour (2nd ed.). Ncw York: John Will'Y N. & Nordin. rio'\\\\. (1999). FlIlId(\/I!U'IIUJ!S oj' 13iOlllt'- SOilS. Eqllilihl'illlll, JIOlio\/l, (\/lId lJeji>rlllatioll (2nd cd.). Ncw York: Springcr-V\\\"r1ag. Wiktorin. C.v.H. &. Nordin, ~\\\\l. (1986). 1,II\/,o(\/\/I(:t;OI\/ [() Prohll. ~crr.v, 1.. Norwood, L., & House. K. (1977). Klll'C po.o;tUl'\\\\.' ,llld So\/l'illg ill Biollll..'challics (Pl'. 87-129). PhihlClclphia: Lea biceps and semimembranosus muscle action in fUllning Fchig('l'. <'Ind cutting (an EMG study). hailS Ortlwl) UL'S S(lC 2, 258. Wilson. S.A., Vigorila, V.J., &. SCf.HL. WN. (1994). Anatomy. Ramsi..'y, O.K. & Wn.'tl'llhcrg, P.E (1999). Biolllcchallit,:-; of tht:' N. SCOIt (Ed.), The Kllee (po 17). Philadelphia: ~'Iosby. kn~c: Melhodological consid('r;ltions in Ihl' in \\\\'i\\\\'o kinl'- matic an:dysis (~f II\\\\(' tibiofl'moral and patellofclIlor;d Wrclenberg, P., Nemeth. G., Lamontagne. M.. ct <II. (199 joint. RC\\\\'i(:w pnp('r. Clillical Biomecll. 1-1, 595-611. P;lssivc knee muscle momcnt <trillS meas.ured in vivo w MRI. Clilliea! Biol1lcclt, I 1(8}, 439-446. Yu, B., Stuart, 1\\\\-1.1 .\u2022 Kicnb;ll'chcr, T., et .d. (1997). Valg \\\\\u00b7'II\u00b7US motion of the knee ill norm.1I lc\\\"d w;dking [lnd st climbing. Clillical Biolllcch, 12(5), 2S6-293. Zcrnickc, R.E, G;lrhammer. J., & Jobe. FW. (1977). Hum pntdlar Icndon rupture. 1 801lt' loillt S1Irg, 59;\\\\, 179-18","Biomechanics of the Hip Margareta Nordin, Victor H. Frank Introduction Anatomical Considerations The Acetabulum The Femoral Head The Femoral Neck Kinematics Range of Motion , \/f Surface Joint Motion Kinetics Statics Dynamics Effect of External Support on Hip JOll1l Reaction Force Summary References Ie","~, Introduction The hip joint is one of the largest and most SLable joints in the body. In contrast to the knee, the hip joint has intrinsic stability provided by its relatively rigid bali-unci-socket configuration. (t also has a orgreat deal mobility, which allows normallocomo- lion in the performance of daily activities. Derange- ments of the hip Can produce altered stress distri- butions in the joint cartilage and bone, leading to degenerative arlhritis. Such damage is further po~ tcntiated by the large forces borne by the joint. -~ Anatomical Considerations The hip joint is composed of the head of the femur and the acetabulum of the pelvis (Fig. 8-1). This ar- ticulation has a loose joint capsule and is sur- rounded by large. strong muscles. The construction of this stable joint allows for the wide range of 1110- tion required for normal daily activities such as walking, sitting, and squatting. Such a joint must be precisely' aligned and controlled, THE ACETABULUM The hip joint (front view) 1. External iliac artery. 2. Ps major muscle. 3. Iliacus muscle. 4. Iliac crest. S. Gluteu The acetabulum is the concave component of the medius muscle. 6. Gluteus minimus muscle. 7. Greate ball-and-socket configuration of the hip joint. The trochanter. 8. Vastus lateralis muscle. 9. Shaft of femu acetabular surface is covered with articular carti- 10. Vastus medialis muscle. 11. Profunda femoris vess lage that thickens peripherally (Kempson et aI., 12. Adductor longus muscle. 13. Pectineus muscle. 14. M 1971) and predominantly laterally (Rushfeld et aI., circumflex femoral vessels. 15. Capsule of the hip join 1979). The cavity of the acetabulum faces obliquely 16. Neck of femur. 17. Zona orbicularis of capsule. forward, olitwarcL and downward. The osseous ac- 18. Head of femur. 19. Acetabular labrum. 20. Rim of etabululll in the hip is deep and provides substantial etabulum. Reprinted with permission (rom McMinn, R.H. static stability to the hip. A plane through the cir- Huchings. R.H.R. (988). Color Atlas of Human Anatomy cumference of the acetabulum at its opening would ed., p. 302). Chicago: Year Book Medical Publishers, Inc. intersect with the sagittal plane at an angle of 40~ opening posteriorly and with the transverse plane at an angle of 60~ opening laterally. The acetabular cavity is deepened by the labrum, a flat rim of fibro~ cartilage, and the transverse acetabular ligament (Fig. 8-2). The labrum contains free nenle endings and sensory end organs in its superficial layer, which may participate in nociceptive and proprio- ceptive mechanisms (Kim & Azuma, 1995). The unloaded acetabulum has a smaller diameter than the femoral head (Greenwald & Haynes, 1972) (Fig. 8-3). The acetabulum deforms about the femoral head when the hip joint is loaded. It under- goes elastic deformation to become congruous with the femoral head, and contact is made abollt the periphery of the anterior, sllperi()l~ and posterior","arLicular surface of the acetabulum (Konrath et al.. Superior 1998). Load distribution of the acetabulum was Anterior studied in vitro in human specimens (Greenwald & I-(aynes, 1972; Konrath et 'II., 1998). Joint reaction forces were simulated to physiological levels. The loading pattern of the acetabulum is shown in Fig- ure 8-3. Removal of the transverse acetabular liga- ment and labrum sequentially did not affect the loading pattern of the acetabulum significantly (Konrath et 'II., 1998). Intact THE FEMORAL HEAD The femoral head is the convex component of the loading pattern of a human acetabulum in vitro with ball-and-socket configuration of the hip joint and tact labrum and transverse acetabular ligament. Note: forms two-thirds of a sphere. The articular carti- pattern was grossly unchanged after removal of the tr lage covering the femoral head is thickest on the verse acetabular ligament. or the labrum, or both, and medi,al-central surface and thinnest toward the pe- therefore those patterns are not displayed. Adapled fro riphery. The variations in the cartilage thickness Konrath. GA.. Hamel. A.I.. Olson. S.A.. et elf. {l998). The ro result in a different strength and stiffness in vari- the acetabular labrum and the trdnSverse clCeiabtJ\/dr ligame ous regions of the femoral head (Kempson et 'II., load transmission of tilt, hlp. J Bone Joint Surg. 80\/'.,(12), . - - -I 1781-1788. Transverse J971 l. Rydell (1965) suggested I hat most load acetabular transmitted in the.: femoral head through the su rior quad,-ant. VOll Eisenharl-Rothe et al. (19 ligament demonstrated in an in vitro study that the ma tude or load influenced tlte loading patlerll on femoral head. At smaller load:s, the load-bea area was concentrated at the periphery of the nate surface of the femoral head. and at hig loads to the center of the lunate and the ante and posterior horns. It is still not known exa how the stresses in vivo on the normal fem head arc distributed. bUl indications from in measurements with an instnll11Cnted prosth head show that the anterior and medial lunat transmitting most 01\\\" the load during daily ac ties (Bergmann et al .. 1993. 1995). Schematic drawing showing the lateral view of the acetab- THE FEMORAL NECK ulum with the labrum and the transverse acetabular liga- ment intact. Adapred (rom KOflrarh, G.A., Helmel. Ai.. Olson, The fen10ral neck has two angular relations s.A., et al. (998). The role of (he acetabular labrum and tile with the femoral shaft that arc important to transverse acetabular ligamenr in (oad transmission of the hip. joint function: the angk of inclinalion of the nec J Bone Joint Surg. 80A(12), 1781-1788. the shaft in the frontal plane (the neck-to-shaft gie) and the angle of inclination in the transv 'plane (the angle of anteversion). Freedom of rno of the hip joint is facilitated bv the neck-to-shaft gle, which offsels the femoral shaft from the p laterally. in 11'10$1 adults. this angle is approxima","125~, but it can vary' from 90 to 135 . An angle ex- Neck Head ceeding 125' produces a condition known as coxa valga; an angle less than 125'\\\" results in coxa vara Greater (Fig. 8-4). Deviation of the femoral shaft in either trochanter \\\\vay alters the Force relationships about the hip joint and has a nontrivial effect on the lever arms to mus- Lateral Medial cle force and line of gravity'. condyle condyle The angle of anteversion is formed as a projec~ Top view of the proximal end of the left femur showing l.ion of the long axis of the femoral head and the the angle of anteversion, formed by the intersection of th transverse axis of the femoral condyles (Fig. 8~5). long axis of the femoral head and the transverse axis of In adults, this angle averages approximately 12\\\"', the femoral condyles. This angle averages approximately but it varies a great deal. Anteversion of more than 12' in adults. 12\\\" causes a portion of the femoral head to be un- covered and creates a tendency tc}\\\\vard internal ro- tation of the leg during gait to keep the femoral head in the acetabular cavity. An angle of less than 12\\\" (rclroversion) produces a tendency toward ex~ ternal rotation of the leg during gail. Both antever- sion and retroversion arc fairly common in chil- dren but arc usually outgrown. The interior of the femoral neck is composed of cancellous bone \\\\vith trabeculae organized into medial and lateral trabecular systems (Fig. 8-1, 8- 6), The fact that the joint reaction force on the femoral head parallels the trabeculae of the medial Neck-to-Shaft Angle system (Frankel, 1960) indicates the importance the s}'stem for supporting this force. The epiphy Coxa vara Normal Coxa valga seal plates are at right angles to the trabeculae angle 125C, angle> 125' the medial system and are thought to be perpen 1DIIl-i angle <.: 125\\\" dicular to the joint reaction force on the femor _ head ([nman. 1947). It is likely that the lateral tr becular system resists the compressive force on th The normal neck-to-shaft angle (angle of inclination of fcmoral head produced by contraction of the ab ductor muscles-the glutcus medius, the gluteu I the femoral neck to the shaft in the frontal plane) is ap- minimus, and the tensor fasciae latac. Thc th proximately 125\\\". The condition in which this angle is less shell of cortical bone around the superior femor than 125' is called coxa vara. If the angle is greater than neck progressively thickens in the inferior region 125\u00b7, the condition is called coxa valga. \\\\Vith aging, the femoral neck graduall.v undergoe 0------------------ degenerative changes: the cortical bonc is thinne and cancellated and the trabeculae arc gracluall}! r sorbed (see Fig. 2-50). These changes may predi pose the femoral neck to fracture. It is noteworth that the fernoral neck is the most cOllllllon fractu site in elderly persons (Case Study 8-1). Kinematics In considering thc kinematics of the hip joint, it useful to view the joint as a stable ball-and-sock configuration wherein the femoral head and aceta ulum can move in all directions.","three planes. Measurements in the sagittal during level walking (Murray, 1967) showed the joint was maxirrwlly tlexed during th swing phase of gail, as the limb moved forwa heel strike. The joint extended as the body m fOl\\\\vard at the beginning of stance phase. ll)um extension was reached at heel-oil. The reversed into flexion during swing phase and reached maximal Ocxion, 35 to 40', prior to strike. Figure 8-81\\\\ shows the pattern of hip motion in the sagittal plane during a gail cyc ---------- Femoral Intertrochanteric Fractures A n 80-year-old woman falls from her own height af losing her balance. She presented with sharp pain ., her hip and an inability to stand and walk by herself. Sh is transported to the E.R. and after a careful examinatio and x-ray evaluation, a right intertrochanteric fracture is d,iagnosed. Roentgenogram of a femoral neck showing the medial and lateral trabecular systems. The thin shell of cortical bone around the superior femoral neck progressively thick\u00b7 ens in the inferior region . \u2022 RANGE OF MOTION The radiograph illustrates a right femoral in- tertrochanteric unstable fracture with separation of the Hip motion takes place in all three planes: sagittal lesser trochanter. The image shovvs osteoporOlie changes (flexion-extension), frontal (abduction-adduction), characteristic of the aging process. The decrease in the and transverse (internal-external rotation) (Fig. bone mass at the femoral neck leads (0 reduced bone 8\u00b77). Motion is greatest in thc sagittal plane, where strength and stiffness as a result of diminution in the the range of ncxion is from 0 to approximatcly 140\\\" amount of cancellous bone and thinning of conical bone and the range of extcnsion is from 0 to 15~. The increases the likelihood of a fracture at the weakest level range or abduction is fTom 0 to 30\\\", whereas that of During the fall. the magnitude of the compressive forces at the femoral neck overcame its stiffness and adduction is somewhat less, from 0 to 25'. External strength. In addition. the tensile forces produced by pro rotation ranges from 0 to 9W degrees and internal ro- tective contraction of muscles such as the iliopsoas gen tation from 0 to 70' when the hip joint is flexed. Less ated a traction fracture at the lesser trochanter level. rotation occurs when the hip joint is extended be- cause of the restricting function of the soft tissues. The range of motion of the hip joint during gail has been measured e1ectrogoniometrically in all ;' _~o_, ~:,,;:h-",":t: .\/ i;: \\\" Extension Abduction Adduction External Internal B rotation rotation c D E Movements of the hip joint. A. Flexion-extension. B, Abduction. C. Adduction. D. External rotation. E. Internal rotation . \u2022 allows a comparison of this motion with that of the the tracking limb; they also showed reduced do knee and ankle. nexion of the ankle and diminished elevation of Motion in the frontal plane (abduction-adduc- toe of the forward limb, tion) and transverse plane (internal-external rota- The range of motion in three planes during c tion) during gait (Johnslon & Smidt. 1969) is illus- mon daily activities such as tying a shoe, sit trated in Figure 8-8B. Abduction occurred during down on a chair, rising [Torn it, picking lip an ob swing phase, reaching its maximum just after toe- from the floor, and climbing stairs \\\\vas measu olT; at heel strike, the hip joint reversed into addue- electrogoniomctrically in 33 normalmcn by John tion, which continued until late stance phase. The and Smidt (1970), The mean motion during th 't. hip joint was externally rotated throughout the activities is shown in Table 8-1. Maximal Illatio swing phase, rotating internally just before heel the sagittal plane (hip flexion) was needed for t st.-ike, The joint .-emained internally rotated until the shoe and bending down to sqUal to pick lip late stance phase, when it again rotated externally. object rrom the noor. The greatest motion in The average ranges of motion recorded for the 33 frontal and transverse planes was recorded du normal men in this study' \\\\vere 12' for the frontal squatting and during shoe tying with the foot ac plane and 13' For the transverse plane. the opposite thigh, The values obtained for t As people age, they use a progressively smaller common activities indicate that hip flexion o portion of the range of motion of the lower extrem~ least 120G abduction and external rotation of atl ity joints during ambulation. Murray and co\\\\\\\\,\/orkers 20\\\" are necessary for caITying out daily activitie (1969) studied the walking pallerns of 67 normal a normal manner. men of similar weight and height ranging in age from 20 to 87 years and compared the gait patterns SURFACE JOINT MOTION of o.lder and younger men. The diffcrences in the sagittal body positions of the two groups at the in- Surface Illotion in the hip joint can be considere stant of heel strike are illustrated in Figure 8-9. The gliding of the femoral head on the a<;etabulum. older mcn had shorter strides, a decreased nmge of pivoting of the ball and socket in three planes aro hip flexion and extension, decreased plantar flexion the center of rotation in the femoral head (estim of the ankle. and a decreased heel-to-noOJ\\\" angle of at the center of the femoral head) produces this 'T\u00b7- .. , '-. ,.","70 --Hip joint ,,,,,-',,,, ----. Knee joint \\\\\u2022, Abduction . ............ Ankle joint 60~ 50 I1,,\u2022: 5 i==\\\"\\\"1--....~.... '\\\"w .,,1 \\\\, o ~ 40~ (j) 5 Adduction ww Internal :sCw> 30~ 1 \\\\ Q, c \/I c '0x .\\\\ :ws ,2 20 .\/ ,\\\" I' uw: \\\"' I ., c ;; 10 , '\\\" \\\\ Q ~ ., ;; C ~ rotation --.l '0 0 .\u2022\u2022.... ..,\/ ...... \u00a3Q. 0514:::::=~....1 ~ c 10 ... ...- 5 \\\"'i...---'I ..... '\\\"0 ................ External c 20 rotation .x'!l 30 60, 100 100 60 100 100 Stance Swing LU phase phase Stance phase Swmg phase Percentage of Cycle Percentage of Cycle A B A. Range of hip joint motion in the sagittal plane for 30 nor- range of motion in the frontal plane (top) and transver mal men during level walking, one gait cycle. The ranges of plane (bottom) during level walking, one gait cycle. Ad motion for the knee and ankle joints are shown for compari- from Johnston, Pl. C. S Smiclt, G.L. (J 969). \/vleasuremcn[ of h son. Adapted from ivlurray, ~J1.p. (1967). Gait as a tolal pattern of joinr morion during waf.l-:.ing_ EvaluMion of an electrogoliiom movement. Am) Phys iVIed, 46, 290. B, A typical pattern for method J Bone Joint Sur~J, 51 A 1083 Differences in the sagittal body positions of older men ing of the joint surfaces. If incongruity is prese (left) and younger men (right) at the instant of heel strike. the femoral head, gliding may not be parallel or The older men showed shorter strides, a decreased range gential to the joint surface and the articular cart of hip flexion and extension, decreased plantar flexion of may' be abnormally compressed or distracted. In the ankle, and a decreased heel\\\"to-floor angle of the center analysis by means of the Reulcaux me tracking limb; they also showed less dorsiflexion of the an\\\" cannot be performed accurately in the hip join kle and less elevation of the toe of the forward limb. cause motion takes place in three planes simul Reprinted with permission from Murray, MP., Kory, R,C, & ously. Locating the center of rotation of the hip Clarkson, 8,H. (1969). Walking patterns in flealthy old men. is essential for prosthetic surgery' of the hip to re Gerontal, 24, \/69-178. struct an optimal lever arm of the gluteus me muscle (Fess)' et aI., 1999), Kinetics Kinetic studies have demonstrated that substa forces act on the hip joint during simple activ (Hurwitz & Anclriacchi, 1997, 1998), The faclo volved in producing these forces must be lI stood if rational rehabilitation programs arc","Mean Values for Maximum Hip Motion in weight, the reaction force on each hip joint will one half of the remaining two thirds, or one thi fhree Planes During Common Activities of body weight; however, if the muscles surroun ing the hip joint contract to prevent swa,ying an Activity Plane Recorded Value to maintain an upright position of the body (e. of Motion (Degrees) during prolonged standing), this force increases proportion to the amount of muscle activity. Tying shoe with Sagittal 124 foot on floor Frontal 19 vVhen a person changes from a two-leg to a singl Transverse 1 leg stance, the line of gravit:v of the superincumbe Tying shoe with body shifts in all three planes, producing momen Sagittal 1 around the hip joint that must be counteracted foot across Frontal muscle forces and thus increasing the joint reacti opposite thigh Transverse 23 force. The magnitude of the moments, and hence t 33 magnitude of the joint rcaction force, depcnds on t Sitting down Sagittal posture of the spine, the position of the non-wcigh on chair and Frontal 104 bearing leg and upper extremities, and the inclin rising from sitting Transverse 20 tion of the pelvis (McLeish & Chamley, 1970). Figu 8-10 demonstrates how the line of gravity in t Stooping to obtain Sagittal 117 frontal plane shifts with four different positions object from floor Frontal 21 the upper body and inclinations of the pelvis: stan Transverse ing with the pelvis in a ncutral position, standi Squatting 122 with a maximum tilt of the upper bod)' over the su Sagittal 28 porting hip joint, sianding with the upper body ti J'>.scending stairs Frontal 26 ing away from the supporting hip joint, and standi Transverse with the pelvis sagging away' from the supporting h Descending stairs 67 joint (Trendelenburg's test). The shift in the grav Sagittal 16 line, and hence in the length of the lever arm of t Frontal 18 gravitational force (the peq)endicular distance b Transverse tween the gravity line and the center of rotation 36 the fernoral head), influences the magnitude of t Sagittal moments about the hip joint and, consequently, t joint reaction force. The gravitational forcc lever ar i'.ile,)1l for 33 normal men. Data hom Johnston, R.C. & Smidt. G.L. and the joint reaction force are minimized when t i.i970), Hip motion measurements for selected activities of daily living; trunk is tilted over the hip joint (Fig. 8-108). (lin Orrhop, 72, 205 Two methods arc used for deriving the magnitu developed for patients with pathological conditions of the joint reaction force acting on the femor of the hip. The abductor muscle group (the glutcus head: the simplified free-body technique for cop medius and minimus muscles) is the main stabilizer nar forces and a mathematical method utilizi during one-legged stance (Kumagai et aI., 1997; equilibrium equations. The simplified free~bo University of California, 1953) technique for coplanar forces was described in d tail in Chapter 7, in Calculation Box 7.1. This tec STATICS nique is used in the hip to cstimatc the joint rea tion force in the frontal plane acting on the femor During a two-leg stance, the line of gravity of the head during a single-leg stance with the pelvis in superincumbent bod:v passes posterior to thc pu~ neutral position (Calculation Box 8-1). The seco bic s)'mphysis, and, because the hip joint is stable, method is a mathematical calculation of the jo an erect stance can be achieved \\\\vithout muscle reaction force on the femoral head using equil contraction through the stabilizing effect of the rium equations for a single-leg stance with t joint capsule and capsular ligaments. With no pelvis level (Calculation Box 8-2). muscle activity to produce moments around the hip joint, calculation of the joint reaction force be- To understand and solve the equations it is ne comes simple: the magnitude of this force on each essaI)' to indicate first the location of the extern femoral head during upright two-legged stance is forces acting on the body during the single-l one half the weight of the superincumbent body. Because each lower extremity is one sixth of body","Roentgenograms utilizing a plumb line (black line) show supporting hip joint_ Again the gravity line has shifted to- that the line of gravity shifts in the frontal plane with differ\u00b7 ward the supporting hip, thus decreasing the joint reactio ent positions of the upper body and inclinations of the force. D. The pelvis sags away from the supporting hip join pelvis. A, The pelvis is in a neutral position. The gravity line (Trendelenburg's test). The shift in the gravity line is simila faUs approximately through the pubic symphysis. The lever to that in C. (Courtes}' of 10hn C Baker. IvI.D., Case vVesrem R arm for the force produced by body weight (the perpendicu\u00b7 serve Unive(sir}~ Cleveland, OhiO} Note: In B, the antalgic gait lar distance between the gravity line and the center of rota- illustrated, which lowers the load on the head of the femu tion in the femoral head) influences the moment about the but alters the load line to a more vertical position. Followi hip joint and hence the joint reaction force. B, The shoulders arthroplasty for arthritis, the abductor muscles are weak a are maximally tilted over the supporting hip joint. The grav\u00b7 atrophic as a result of the disease process and the surgery. ity line has shifted and is now nearest the supporting hip. External support such as a cane should be used until the a Because this shift minimizes the lever arm, the moment ductor muscles are rehabilitated. The best indication for a about the hip joint and the joint reaction force are also min- rehabilitated abductor muscle is the lack of limping. imized. C, The shoulders are maximally tilted away from the","on a free\u00b7body diagram (Calculation Box Fig. required for stability. The moment arising from th 1)_ Because the body is in equilibrium (i.e\\\" the superincumbent body weight (equal to % 'IN) mu of the 11''lOmenls and the sum of the forces both be balanced by a moment arising from the force the abductor muscles_ The rorce produced by the s zero), the ground l'eaction force is equal to the perincumbent hody weight (% W) acts al a diSlan 'Q:l-,witatwllal force of the body, which can be divided or b rrom the center of rotation of the hip (Q), thu producing a moment of % Vt\/ times b. The force pr 1WO components, the gravitational force of the duced by the principal abductor, the glute leg (equal to one-sixth body weight) and the medius, designated as A, acts at a distance of c fro force (equal to five-sixths body weight). the center of rotation, producing a counterbalan body is divided at the hip joint into two ing rnomcnt of A limes c. For the body to remain moment equilibrium. the sum of the moments mu h-\\\"e-DC)(lIeS- The main coplanar forces and moments equal zero. In this example, the moments actin on these free-bodies must be determined. upper free-body is considered first (Calculalion ;1j~IJOX Fig. 8-2-2). In this free-body, t\\\\\\\\'o moments are ------------------ Simplified Free-Body Technique for Coplanar Forces The stance limb is considered as a free-body, and a free-body lion, simplifying assumptions are made in determining the di- diagram is drawn. From all of the forces acting on the free- rection of this force (Mcleish & Charnley, 1970). Furthermore. body, the three main coplanar forces are identified as the forces produced by other muscles aCiive in slabilizing the hip force of gravity against the foot (the ground reaction force), joint are not taken into account. The joint reaction force (]) \\\\,.'\/hich is transmitted through the tibia to the femoral has a known point of application on the surface (lunate) of condyles; the force produced by contraction of the abductor the femoral head bur an unknown magnitude, sense, and .'.; muscles; and the joint reaction force on the femoral head. line of application. The ground reaction force ('IN) has a known magnitude equal to five-sixths of body weight and a known sense, line of ap- The magnitudes of the abductor muscle force and the plication. and point of appliCc1tion. The abdu([or muscle force jOint reaction force can be derived by designating all thr~e (A) has a known sense, a known line of application, and point of application estimated from the muscle origin and in- nforces on the free-body diagram (Calculation Box Fig. 8~_1\u00b7 sertion on a roentgenogram but an unknown magnitude. Be- cause several muscles are involved in the action of hip abduc- and constructing a triangle of forces (Calculation Box Fig: 8-1-2). The muscle force is found to be approximately two times body weight, whereas the joint reaction force is some- what greater. Force J Intersection point J' \/ \/Force A 2W\/ I I ,t ,._wt\/\/ I ForceJ I 2_75 W 1 Force W ! Calculation Box Figure 8-1-1. Calculation Box Figure 8\u00b7'-2. &--------------------------------------~---------------------------------------------- - - - - - ,.- . , -:-.-_ ..","External Forces Acting on the Body in Calculation Box Equilibrium During a Single-Leg Stance Figure 8-2\u00b71. Calculation Box Figure 8-2-1 shows external fOKes acting on the body in equilibrium during a single-leg Slance. The ground reaction force is equal to body weight (W). The gravi!ational force of the stance leg is equal to one-sixth of body weight; the remaining force is equal to five-sixths of body weight. w The internal forces acting on the hip joint are founel by sepa- 5\/6 W : rating the joint into an upper and lower free-body; the Lipper b- _ . _ \\\": free-body is considered first. In this free-body, two moments are required for stability. Moment equilibrium is attained by Calculation Box the prOduction of two equal moments. A moment arising Figure 8-2\u00b72. from the force of the abductor muscle (A) times abductor force lever arm (e) counterbalances the moment arising from A = 2W Ax =: A \u00b7sin30~ the gravitational force of the superincumbent body (5\/6 W) Ax = O.5A ~ W Ay := A\u00b7cos30'\\\" times gravitational force lever arm (b), which tends to tilt the Ay = 0.8 A = 1.7 W pelvis away from the supporting lower extremity. Q, center of rotation of the hip joint. Calculation Box Figure 8-2-3. Ay 30\\\" Force A is equal to two times body weight and has a direction Ax of 30' from the vertical. The magnitudes of its horizontal (A,) and vertical (A) components are found by vector analysis. Perpendiculars are drawn from the tail of A to a horizomal and a vertical line representing A. and A\\\" respectively. A, and A, can then be scaled off. Allernatively. trigonometry is used to find the magnitudes of the components. .._ - - - - - -, - - . _ -._--~._._-_._-_","clockwise arc arbilraril~' considered to be positive Fig. 8-2-2). This is particularly important in pros and lhe counterclockwise moments arc considered thetic replacements of the hip joint (Delp & Maloney. 1993; Free & Dell', 1996; Lim et al .. 1999 be negative. Thus, Sutherland et 'II., 1999; Vasavada et 'II., 1994). The center of motion can be altered by the prosthctic de (Y.,W x b) - (A x c) = 0 sign and the lever arm for the abductor muscles can be slightly changed by slu-get)! techniqucs. A change A= YoW x b of the center of location of the hip joint can de crease the abduction force by more than 40(1'0 and -'---- thereby the generated abduclor moment b~} almos c 50% (Dell' & Maloney, 1993), Figure 8-11 illustrate the relationship of this ratio to the joint reaction To solve for A it is necessary to find the values of force. ;\\\\ low ratio (i.e., a small muscle force leve ann and a large gravitational force lever arm) yield and c. The gravitational force lever ann (b) is a greater joint reaction force than docs a high ratio roentgenographically. Because the cenler of A short lever arm of the nbduc(ol- musclc force, a in coxa valga (Fig. 8-4), rcsults in a sTllall ratio and gravity must lie over the base of sUppOrl, a plumb lInls a sornewhat e1cvated joint reaction force. Mo\\\\' ing thc greater lrochanter latcrally during lata! hip line intersecting the heel can be extended upward; a replacement lowers the joint reaction force. as it in creases the lever arm ratio by increasing the muscl line drawn from the center of rota- force lever arm (Free & Delp, 1996). Inserting a prosthetic CLIp deeper in the acetabulum reduce in the femoral head (Q) to the line represents the gravitational force lever ann, thereby increasing the ratio and decreasing the joint rcaction force. I \\\"\\\"\\\"'\\\\IlOe b. The muscle force lever arm (c) is simi- is difficult. howc\\\\'cl: to change the lever an11 ratio in such a way as to reduce the joint rcaction force sig .~.' larl~! found by identifying the glutcus medius mus- nificantly beenuse the curve formed from plouing the ratios becomes asymptotic when the ratio of c to I cle on a roentgenogram (Nemeth & Ohlsen, 1985, b approaches 0.8 (Fig, 8-1 I). I 1989) and drawing a perpendicular line from the DYNAMICS L center of rotation 01\\\" the femoral head to a line ap- The loads on the hip joint during dynamic activi ties have been studied by several investigator proximating the gluteus mcdius muscle tendon. (Andriacchi ct aI., 1980; Draganich c{ al.. 1980 English & Kilvington. 1979: Rydell, 1966). Using a In this example, a value for A of two times body force plate system and kinematic data for the nOI\\\" Illal hip, J. P. Paul, 1967. (Forces at the human hip weight was derived from thc static free-body diagram joint. Unpublished doctoral theses, University o Chicago) examined the joint reaction force on th and confil'med by instll.llnentcd in vivo measure- femoral head in normal men and women during gait and correlated the peak magnitudes with spe ments (English & Kilvington, 1979; Rydell, 1966). The cine muscle activity recorded electromyograph i cally. In the men, two peak forces were produced direction of force A is found from a roentgenogrnrn to during the stance phase when the abductor mus cles contracted to stabilize the pelvis. One peak o be 300 from the vertical. The hOI'izontal and vcrtical approximately four times body weight occurred just nfter heel strike, and a large peak of approxi components of this force are found by vector analysis matel:v seven times body weight was. reached jus before toe-ofr (Fig. 8-12A). During foot flat, th (Calculation Box Fig. 8-2-3). The hOl-izonlal compo- joint reaction force decreased to approximately nent (AJ is equal to body\\\" weight; the vertical compo- nent (A y ) is approximately 1.7 times body \\\\veight. Attention is then directed to the lower free-body (Calculation Box Fig 8-3-1). The gravitational forces (Wand II. W) are known. The joint reaction force (force J) has an unknown magnitude and direction but originates from the most narrow joint space in the radiograph and musl pass through the esti- mated center of rotation in the femoral head. The magnitude of force J is determined by finding the horizontal and vertical force components and adding them (Calculation Box Fig. 8-3-2). The value of J is found by vector addition (Calcu- lation Box Fig. 8-3~3), and its direction is measured on the parallelogram of forces. The joint reaction force on the femoral head in a single-leg stance with the pelvis leveled in the horizontal plane is found to be approximately 2.7 times body weight, and its di- rection is 69\u00b7 fTom the horizontal (Calculation Box Fig, 8-3-4). A key factor influencing the magnitude of the joint reaction force on the femoral head is the ratio of the abductor muscle rorce lever ann (c) to the gravitational force lever arm (b) (Calculation Box","~. : I Free-Body Diagram of the Lower Extremity J y c\u00b7\u00b7 2.5W Tana A Tan a In Calculation Box Figure 8~3\u00b71, the supporting lower ex- Jx tremity is considered as a free-body, and the forces act- 2.5 ing on the free-body are identified. A, abductor muscle force; J, joint reaction force; 1\/6 W, gravitational force of a 69 the limb; W, ground reaction force; Q, center of rotation of the hip joint. Jx W Calculation Box Figure 8~3-3, In Calculation Box Figure 8-3-2, the forces acting on the lower free-body arE> divided into horizontal and verti- J 2~7 W cal components. Because the body is in force equilibrium, the sum of the forces in the horizontal direction must .I. equal zero and 50 must the forces in the vertical direc- tion. The horizontal and vertical forces are added and the A magnitudes of J.: and J( are found from force equilibrium equations: A,~-J,~O aA, ~~J.- '\/W\\\",\\\" W ,- I.7W-J.-'\/W W~O A,~W J,. - W J..., 1.7 W ~,~ \/. W From the Calculation Box 82 A. - I.7W Calculation Box Figure 8-3-4. Addition of the horizontal and vertical components J..- and J, is performed graphically in Figure 8-3-3, and the joint reaction force (J) is scaled off. A parallelogram is con- structed and the diagonal of the parallelogram indicates the inclination of the force J. Its inclination in relation to the horizontal plane is measured (n) on the parallelogram, Alternately, trigonometry is used to find the direction of J using tangent equations (Fig. 8-3-4). The joint reaction force has a magnitude of approxi- mately 2.7 times body weight and acts at an angle 69\\\" from the horizontal, w w Calculation Box Calculation Box Figure 8~3~1. Figure 8-3-2.","Men 7.0 6.0 7 'l 6 a> 5.0 :c 'ffi ~ a> 5 >- \\\"e0 ;'ff;i ~ 4.0 >- 4 ~ u0. 1S @. 3 ~ ua~. 2 3.0 Upper and 60 100 Percentage of CyCle lower Women > limits of 10< angle of 2.0 ~..,._.,......,_..,.._.--..,._.,.......;5,,0:..'.., inclination o 0:2 0:4 0:6 0.8 i of abductor muscle !1Bm Ratio of c to b force line _ The value of the ratio of the abductor muscle force lever 60 100 Percentage of Cycle I, arm (e) to the gravitational force lever arm (b) is plotted against the joint reaction force on the femoral head in Muscle AClivity During Slance Phase of Gait r\\\"======! - -GSlle\/lmeu:tseMm'all~O,SmUuSs units of body weight. Because the line of application of E~tellsors Semimem!)r,lllOSUS I the abductor muscle force (its angle of inclination in the frontal plane) has finite upper and lower limits (10 and 1-------Biceps tomor,s ~~~~~~~F1'\\\"''Tensor [osciac 50\u00b0), the force envelope is plotted. The curve can be uti\u00b7 IIi\\\",,\\\",S,lrtOri.us _ Gr,lc,bs I lized to determine the minimal force acting on the Reclus femoris femoral head during a one-leg stance if the ratio of ( to b I is known. AdiJpced from Frankel. VH. (960). In The Femoral Neck: Function, Fracture Mechanisms, Internal fixation. Spring- I field: Charles C. Thomas, 8---------------- Gluteus med,us Abductols Gluleus minimus .-==:==~AddUCIOIS .\\\\dduc!or magous Adductor IOr1(Jus Adductor brevis 100 60 body weight because of the rapid deceleration of c Percentage of Cycle the bodv's centcr of ~gra.vi'lv. Durin lT the swing~ .' t> phase, the joint reaction force was influenced by contraction of the extcnsor muscles in decelerat- Hip joint reaction force in units of body weight during walking, one gait cycle. The shaded area indicates varia- ing the thigh. and the magnitude remained rela- tions among subjects. A. Force pattern for normal men. tively low. approximately equal to body weight. 8, Force pattern for normal women. Adapted from Paul, IP (1967). Forces at the human hip joint. Unpublished doctoral the\u00b7 In the women, the force pattern was the same but sis. University of Chicago. C, Muscle activity during stance the magnitude was sorncwhat loweI~ reaching a max- phase of gait. The first peak corresponds mainly for the ex- tensor and abductor muscles. The last peak. is for the flexor imum of only approximalely four times body weight and adductor muscles. Adapted from the University of Califor- nia. (1953). The pattern of muscular acrivity in rhe lower excrem at late sfance phase (Fig. 8-128). The lower magni- i!'\/ during ,\u00b7valking. Univ Cal Prosthet Dev Res Rep, 2(25). 1--4\/. tude of thc joint reaction force in the women may \u2022 have been the result of several factors: a wider female pelvis. a difference in rhe inclination of the fcmoral neck-to-shaft angle, a difference in footwear. and dif- ferences in the general pattern of gait.","1400 Walking (0.9 mtsec) In \\\\\\\"ivo ml..'asurl..'ll1enls of lhe forces acting - - Ground reaction force 1200 .........u\\\". Force on prosthesis instrumented hip joint prosthesis demonstra lower joint reaction force or the femoral head 1000 t\\\\ ing the stance plwse or gail compared with ex mcnsuremcnts and calculations (Rydell, 1965 ..~ 800e , 600 8-13;\\\\). At a faster cadence. the forces \u2022.\\\\Cling o 0 4 prosthesis grcatl~' increased because of an inc lL in muscle ac(ivi(~' (Fig. 8-138). At both cade 400 orthe magnitude the forces during swing phas 200 arproxirnatel~:half that during stance phase. l~lble 8\u00b72 summarizes the typical peak joint A Walking (1.3 m\/sec) on the hip joinl load e.\\\"pressed as bod~1 weight 1800 - - - - Ground reaction force different studies and with differ\u00b7ent methods 1600 .............\\\" .... Force on prosthesis pattern of loading for \\\\valking is similar for all 1400 ies, but the magnitude of joint peak load differ ternal measurements gencraHy yield higher lated peak force on the hip joilll while inslrum implant in vivo measuremcnts ~'ield lower forces. There are man)' reasons 1'01' the diffe for example, the melhod and instn1l11cnwtio normal hip \\\"crsus the \\\"abnormal\\\" instrulllcnte plum. the gait velocity, and age. Activities othe \\\\\\\\\u00b7alking, such as stair ascending\/descending, loads of around 2.6 to 5.5 body wciglll Illea 1200 ~ 1000 , 'e\\\" 0 800 ,ImI!DJI lL Range of Typical Reported Peak Hip Joint Forces From Selected Studies ;!- 600 or-,400 Reported 200 Peak Force ,1 -A_c.,t-i.'v.'i..t.y_-_B.W_---_..._ - Instrument ation Reference i -_.,.._,._-- Bergmann 1993, 19 i i 3 Walking 2.7-4.3 Insirurnented SlanceDphase 1 2 implants Swing phase 2.7-3.6 Instrumented Kolzar et a implantS 1991 Time (seconds) B 2.7 Instrumented English et implants 1979 1.8-3.3 Instrumented Rydell et a implants 1966 Forces on an instrumented hip prosthesis during walking. Walking 4.9-7.0 EIviG Paul, 1967 45-7.5 \/force plate The broken line represents the force on the prosthesis, and 5.0-8.0 Crowninshi the solid line represents the ground reaction force. A. 2.2-2.8 EIviG et al.. 19 fforce plate Walking speed 0.9 m per second. B, Walking speed 1.3 m Rohrle et a ElvtG 1984 per second. An increase in muscle activity at the faster ca- fforce picHe van den Bo dence resulted in higher forces on the prosthesis. Adapted accelerometers et aI., t9 from Rydell, tV. (1965), Forces in tfle hip-joint. Parr If: Intravital measurements. In R.M. Kenedi (EdJ. Biomechanics and Related Sio-Engineering Topics (pp. 351-357). Oxford: Pergamon Press. BW. body \\\\'1elght; EMG. electromyography","~--------'--'---'-\\\"---'------\\\"'-----r of a femoral neck fracture allowed a subseq Fatigue Fracture of the Hip determination of the forces acting on the imp during activilies or daily living (Fig. 8-14) (Fra '1\\\\.\\\", 64-year-old, very active retired man experienced a el aI., 1971). Although the device measured fo \u00b7M femoral neck fracture after changing his training on the implant and not on the hip joint, it was ,'regime to prepare for a marathon. The fracture was sible to determine the proportion of the transmitted L1nough the device and to calcu '.>~. classified as a faligue fracture caused by overload of -, the hip joint. the total load acting on the hip joint by mean ;~ static analysis. In the case illustrated in Fi 8-14. the nail plate transmitted one fOllrth of lOtalload. Strong forces aCling on the nail plate were countered during such diverse activities as mo onto a bedpan, transferring to a wheelchair, walking. The magnitude of the forces was gr modified by skillful assistance frol11 lhe nurs therapist to control the patient's movement. Fo of lip to fOllr limes boely weight acted on the joint when the patient used the elbows and hee elevate the hips while being placed on a bed (Fig. 8-15), but these forces were greatly red through the lise of a Lrapeze and assistance from attendant (Fig. 8-158). A 5-kg ex.tension tractio the hip had little effect in modifying the forces ing on the hip joint. Exercises of the foot and a increased these forces. Case Study Figure 8-2-1. The figure shows an MRI (frontal view) of the pelvis and both hip joints. The fracture is seen in the left femoral neck distal to the femoral head. The fracture is believed 10 have occurred during running and after an extensive change of training program. Because of the high repetitive I?ading, muscle fatigue, and the change in the load pat- tern, on the hip joint and femoral neck, the bone fractured. with an instnlmentcd hip implant (Bergmann et al., An instrumented nail plate in the proximal end of the 1995; KOlzar et aL. 1991). The highest magnitudes of mur was used to determine the forces acting on the i load during daily activities are measured dllling plant during the activities of daily living following fra stair climbing and getting up from a low chair when of the femoral neck. In this ca5e, the nail plate was fo the hip is flexeell1lore than 100\\\" (Catani et aI., 1995; to transmit one fourth of the total load on the hip jo Johnston et aI., 1979). Co-contraction of the bi- articular muscles was evident during these activities. Running and skiing lIsing accelerometers yielded calculated forces up to eight limes body weight in middle-aged and older people (van den Bogert et al., 1999) (Case Stlldy 8-2). Insertion of an instrumented nail plate in the p'-oximal femur arter osteotomy or during fixation ...., ...,:","AB Usc of the instrumented nail plate demonstr that, for a bedridden patient with a fractu A, When the patient used elbows and heels to elevate the femoral neck, the forces on the fernoral head hips while being placed on a bedpan, the force on the tip ing activities of daily' living approached those of the instrumented nail was 670 N. With a spica cast, the iog walking with external supports. These stu force on the tip of the nail was 190 N. B, The use of a support clinical protocols for carly mobilizatio trapeze and assistance from an attendant reduced the patients and decreased bed rest for patients force to 190 N without a cast and to 70 N with a spica cast. hip fractures. The magnitude (approximatel Reprinted \\\"vith permission from Frankel, V H. (7973). Biome- Nlll) of the moments acling on the nail-plate . chanics of the hip. In R. G. Tronzo (feU Surgery of the Hip Joint lion in the transverse plane (i.e .. during inte (.0,0. 105-125). Philadelphia: Lea & Febiger and extcrn~ll rotation) was only approxirnatel)! half the magnitude (18 Nm) of the moments ac in the frontal plane (Le., during abduction) many activities. EFFECT OF EXTERNAL SUPPORT ON THE HIP JOINT REACTION FORCE Static anal.\\\\\u00b7sis of the joint reaction force on femoral head during walking with a cane dem strates that the cane should be used on the side posite the painful or operated hip. Neumann (1 High and low load on the hip joint during daily activities. Raising from a low chair produces approximately 8 times body weight (A). Walking with a cane on the ipsilateral side of the affected hip produces approximately 3.4 times body weight (B), and walking with a cane on the contralateral side of the affected hip reduces hip joint load substantially to 2.2 times body weight (C). This figure illustrates how load on the hip joint can be manipulated by simple means (X denotes affected hip).","-I :i:::~C::I::J::r:S:~ t:~::r::e~h: i::~re:~~o<~Oint Rea~:~::e:::C:uSCle force (E)was then found from the I faKe acting on the femoral head in Ihe late swing phase of momenl relationship i the gait cycle for an 8\u00b7year-old boy INeighing 24 kg and T ::::: Fd, I wearing a )ong-Ieg brace. The main muscle force was pro- where F is the extensor muscle force and d is the perpendicu~ duced by contraction of the gluteus maximus muscle and lar distance from the center of rotation of the femur to the identified through electromyography. The torque about the middle of the gluteus maxim us muscle. Distance d was mea., hip joint \\\\ivas calculated according to the formula sureej from a roentgenogram and found to be 3.2 em, From T ~ la, H'e equation E;::;: TId, the muscle force on the normal Side', where ..\\\"as calculated to be 338 N, and on the braced side, 600 N. T is the torque expressed in newton meters (Nm) The joint reanion force on the femoral head (J) is equal to I is the mass moment of inertia expressed in newton meters the muscle force (E) minus the gravitational force produced times seconds squared (Nm sec!) by Ihe weight of the limb (W,). In this example, W L \\\\\u00b7\\\\las esti- is the angular acceleration in late swing phase, expressed mated to be 40 N. -;,- in radians per second squared (rlsec 1). On the normal side, On the braced side, In the case of (he braced side. I = I , .;. I;; where J = E-\\\\iV, J = E -\\\\iV, is the mass moment of inertia of the leg J = 338 N - 40 N J=600N-40N is the mass moment of inertia of the brace. J = 298 N. J = 560 N. On the normal side, On the braced side. Thus, tile Joint reaction force on the femoral head in the I \\\"\\\" 0.45 Nm se(' br~1Ced limb v\\\"as over 80% higher than the force in the non~ 1 ;.cc 0.45 Nm sec; + 0.35 Ntn sec' braced limb, reaching more than two times body weight. n=: 24 rlsec'. n = 24 rlsee\\\" Thus, Thus, I = 0.45 Nm sec:' T = (.45 Nm sec) + 35 Nm sec!) .: ~ x 24 rlsec~ x 24 rlsec~ T ~ 10.8 Nm. T ~ 19.2 Nm. I 0~--- studied the effects of cane use in 24 subjects with a a large push may not be possible because of a ,;:: mean age of 63 years. During walking, the e1ec- of strength in the upper extremities. tromyographic activity of the hip abductor muscles The use of a brace on the leg may aller the f was measured, Neumann found that usc of a cane on the hip joint but may not always reduce the on the contralateral side of the affected hip joint, reaction force on the femoral head. An ischial with careful instructions to use with near maximal leg brace used in the treatment of Perthes' dis effort, could reduce the muscle activity by 42% (Fig. raises the joint reaction force during late swing p 8-16). This calculates to a reduction of approxi- because the large mass moment of inert ia o mately one times bod~; \\\\veight from 2.2 body weight brace results in a higher extensor muscle force with a cane, compared with 3.4 body weight with- ing this part of the gait cycle (Calculation Box 8 Out a cane. These studies give important inforllla~ lion to the clinician about ways to moderate the SUl1lmary load for the patient with hip problems. 1'; The hip JOll1t is a ball-and-socket joint Such use reduces the force on the femoral head posed of the acetabulum and femoral head, of the painf-ul joint without necessitating an anlalgic body position. Acane used on the side of the painful 2 The thickness and mechanical properties o hip works through a shoner levcr arm and thus an cartilage on the femoral head and acetabulum even greater push on the cane is needed to decrease from point to poinl. the joint reaction force. For the olcler patient, such -_.~,","3 Hip llexion of at lca~\u00b7a 120\\\", abduction of at Fl\u00b7ss.\\\\', ~1.I-1.. ;\\\\'Diaye, A.. CalTd. J.P.. et :II. (1999)_ Lo least 20\\\", and extenwl rOl<.l.lion of at least 20\\\" are necessary for can}'ing out daily activities in a nor- tht..\u00b7 l\u00b7{.\u00b7lltl-r or rOlation of IIII.' hip. Sl\/r.g nmliol A\/\/at, mal manner. 24;-250. \\\\4 A joint reaction force of apprOXill'latc1y three timcs body weight acts on the hip joint during a sin- orFI'~lnkd, V.H. (19;3). Biollll'challil:s the hip. In R.G. T gle-leg stance with the pelvis in a neutral position; (Ed.), Slll'.~t:ry o( I!lt' Hip }Oil\/l (pp. 105-125). Phil~ldl. its m;gnitudc varies as the position of the upper lea &. Fdlif!l'r. body changes. _~'> The magnitude of the hip joint reaction force is Frankd. V.H. (1960). In nUt FI.'J\/ulI\\\"iI} Nt'd: {-'Wlclioll. F infiuenced by the ratio of Ihe abductor muscle force .\\\\-1f.'(:IUllli:'\/II.\\\\, \\\"\/lenla! FixaTioll. Springfidd: Char and gravitational force lever anns. A low ratio yields a greater joint reaction force than does a high ratio_ TlwllWS. ;;_~ The hip ,joint reaction force during gail reaches Fr'lnkd. V.H .. BurSil'in. A.H .. L~\u00b7grl\u00b7. L., l't al. (1971). Th levels of three to six limes body weight or more in stance phase and is approximately equal to body L.lil: nail. ) BOIH' 10illl SIII\\\"~. 53:1. 1232. weight during swing phase. Free, S.A. & Oelp, S.L. (1996). Trochantt.'rll.: transfer i j.7 An incrense in gait velocity increases the mag- nitude of the hip joint reaction force in both swing hip n:pJal:i.:IlIl.:nl: Effecls on Ilit' lTlOfllL'llt arms nnd and stance phase. gellt..'ralillg c'lpadtic:;s of Ihe hip abductors. J Onlw ,'8 The forces acting on an internal fixation device 1-I{2L 1-15-250. during the ~\\\\ctivitie; of daily living vary greatly' Gn.\u00b7em\\\\'~a1d. A.S. & 1-I<I\\\\'llI,:S, D.W. (1972). Weight-hcaring depending on the nursing carc and the therapeutic ill lhe human hip j{~Jinl..! BOIlt' .!Oilll Siltg. 5-1B( I), 15 activities undertaken by the patient. Hurwitz. D.E. & Andri.tt:(\\\"hi. '1'.1>. (1998). Biomechanics \/9 The lise of a cane or a brace on the leg can al- tcrthe magnitude of the hip joint reaction force. hip. III J.J. Cdbgh'111. A.G. Rosl'nberg. &. I-I.E. R REFERENCES (Eds.1. The: Adult flip (pp. 73-85). Philaddphia: Lipp Andriacl:hi. T.P.. Andersson. G.B .. Famil:r. R.W., Stern. D.. Raven Publishers. G,t!anil', J.O. (1980). r\\\\ study of to\\\\\\\\'er-limb medlanics dur- ing stair\u00b7dimhing. J BOllI.' Johu Surg, 62.-1. 749. Hllr\\\",it;',. D.E. & Andri~\\\\(:(\\\"hi. T.P. (1997). Biolllcl:hanks Bergmann, G., Graichl'll. E, & Rohlm=lIl1l. A. (1993). Hip joint hip .tlld the knl'l'. In ~'1. Nordin, G.B.J .\u2022\\\\ndnsson. & 1~'H.ling during \\\\V,lIking i.lIld running llh..\u00b7.ISurcd in IWo pa\u00b7 tknts. 1 Bio\/lw:h, 26(8),969-990. POPl' (Eds.) . .\\\\lusculoskclewl Disorders ill {Itt' Irork Bergmann. G.. Graichen. E. & Rohlmann, A. (t995). ts slair. Principles (Jud Prauice (pp. -186--196). Phila(k']phia: M cast: walking a risk for tht: fi.X<lli(lll of hip implants?} 13io- IlIe,''', 28(5), 535-553. Year Book. Catani, F.. Hod!!(', r\\\\ .. ~'talln. R.W.. et ::d. (1995). The 1\\\"011.; of Inrn;lIl. V.T. (19-47). Flll1l:lional aspects of t!ll' abductO museul\\\"r co:eontr<lClion of the hip during mon.\u00b7men!. Chi,. Orgalli ;\\\\1ov, 80(2), 227-236. c1es of thl' hip. J BOllI.' loim Sll\\\"~. 29:\\\\. 607. JohnslOn, R.C., Br~Hl(I, R.A .. &. Crowninshicld. R.D. ( Crowllinshidd, R.D .. Johnston, R.C.. Br<lnd. R.t\\\\. (1978). The eHccts of walking no'locity and agl' on hip kint:m<ltics and Re('onslnH:lioll of tht' hip. } BOI\/t' Join, Smg. 6 kinetics. Clill Or\/hop Rd Ues, 132,140-14-\\\\. 646-652. Ddp, S.L. &. Maloney, \\\\V. (1993l. Effects of hip Centcr loca- tioll on the momcnl-generating cilpacity of the l1luscks.) Johnston. R.C. & Smidt. C.L. (1969). !\\\\leasur(,llll'nt o 8'0mi'd,. 26(5). 485-499. join! motion during walking. Evaluation of 'tll I'll' Drng::lllil\u00b7h. L.F.. Andrincchi. T.P.. Strongw::llcr. :\\\\.1\\\\'1.. ct ~\\\\1. niOllll'tric Illt.'lhod. 1 BOll...' loiJ\/! Sll}\\\".~. 51:\\\\, 1083. or(l980). Electronic tlll.:aSLlrcrnent instantaneous fOOL- Johnston, R.C. & Smidl. C.L. (1970). Hip motion tlll floor conl;:\\\\ct paltl'rns during gait. 1 BiOlIICdl. 13. S75. English. T.A. & Kilvington, M. (1979). In \\\\'ivo re('ord~ of hip m('Il{S for sell-tted .\\\\Ctidties of daily li,\u00b7ing. efill O IO:.lds using ::1 fl'llloral impblll with lelemetric output (a 72. 105. preliminary l't:ponl. 1 Biollled ElIg, 1(2), 111. Kcmpson, G.E., Spin.'y. c.J .. Swanson. S.A.V.. cl at. ( Patk'rns of C<lrtila~1' stiffnt..'ss on normal and dC~Cl human femoral he;ds, J liiO\/IIt'ch, -I, 59;. - Kim, Y.T. &: Azurll.l, H. (1995). The lH.'I'\\\\'e t,;ndings of etabular \\\"tbrum. CfiJl Or\/hop, 320, 1;6-181. Konrath, G.A., Hamel. A.1 .. Olson, S.r\\\\ .. d .d. (19981. T of the aCI'I.dHlbr labrum and the (r~\\\\IlS,'e..SI' :lcL'(ablll ;l11lt.:lIt in load transmission of the !lip. J (JOllt~ loill 80A(I2I. t781-1788. Kotzar. G.~L Davy. O.T.. Goldberg. V.;\\\\1., cI al. ( TcJemilriZL'd in \\\"j\\\\'o hip joint forcc dilta. A report o ll<ltit.:IHS aftcr 10iai hip sllrgery. 1 Ort\/wp Nt's, 9. 621 Kumagai. iv1.. Sliiba, N., Higuchi, F.. et a!. (19971. FUll t.:\\\\'aIU:llion of hip abductor mllSC!<;S with llSI' of m. resonance imaging. 1 Orlhop Rt,S, 15(6),888-893. lilli. l.A .. CIl\\\"mi(;h;lel, S.W.. &. C<lbancla, M.E. (19991 llH:chanics of lOUt! hip ;lrlhroplnsly. AI\/ot UI:C, 2 t 10-t 16. j\\\\'kLl'ish, R.D. & Chilrnh:y. J. (1970). Abduuion forct's one-!l.'ggcd st~lnc('. J B;oll\/cch. 3, 191. ;\\\\'ld,linn, ~R.H. &: Huchil1!.;s, R.H.R. (1988). In C%}\\\" Il HI\/lllml AWIlO11\/Y (2Il1.! cd., p. 302). Chic,lgO: )\\\\:.11 ,\\\\-kdic<ll Publishl'rs, Inc MlllT~I\\\\'. ~LP. (1967).. G.dt <lS ,I lOt~t1 pattern of moveme 1 pjlYs .lled, -16, 290.","\\\\-!urray, i'\\\",1.P., Kor.\\\\', R.C., &: Clarkson, 13.11. (1969). Walking Re!uh'd Bio-LII~il\/ecrilig Topics (pp. 351-357). Ox patterns in he:dthy old nH:n. } Geroll\/ol, 2-1, 169-178. f\\\\:rgamon Press. Sutherland, A.G., D'Arcy, S .. Srn:lrt, D., et al. (1999). Ab Nemeth, G. &: Ohlsen, I-l. (1985). In vivo moment arm lengths tor muscle weakness and stress around acetabu!:lr co nents of total hip arthroplasty: A finite dement ana for hip extensor muscles at difTerent angles of hip fle\\\\ion. 1111 Orthop. 23(5), 275-278. } Biolllech, 18, 129-149. University of California. (1953), The pattern of muscula Nemeth, G. & Ohlsen, H. (1989). rvlolTlel1t arms or hip abduc- tivity in tht: lo\\\\\\\\'er extremity during walking, (jllll tor and adductor muscles in vivo by computed tomogra\u00b7 Pros\/hd DcI' Rcs Rep, 2(25). 1-41. phy. Cfill 13iolllccll, 4, 133~136. van den Bogert, A.J., Read, L., &. Nigg, B.rv1. (1999). An ; Neumann, D,A, (1998). Hip abductor JllLlscle activity as sub- sis of hip joint loading during walking, running and jects with hip prostheses walk with dirrerL~nt methods of ing . .lIed Sci Sports, 31(l), 131-142. 'using a cane. Pllys Ther, 78(5),490-501. Vas:lvada, A.N., Delp, S.L., \\\\.laloney. \\\\V.J., et a!' (1994). IWhrle, H., Scholten R., Sigolo!to, C., et al. (1984). Joint pens;:lling (or changes in Illuscle length in total hip <l forces in the human pelvis-leg skeleton during walking. } Biolllcch, 17, 409-424. pbst~,. Effects on tllL' llHHTll'nl gt:nt:rating capacity o Rushfcld, P.D., \\\\tann, R.\\\\V., &: Harris, W.H. (1979). Influence muscles. Cfill OnllOp. 302. 121-\u00b7133. of cartilage geometry on the pressure distribution in the VonF.isenhart-Rotht:, R.. Eckstein, r.. ~luller-Gerbl. rlit., human hip joint. Sciellce, April 27, 204(4391), 413-415. Rydell, N.W. (1966). Forces acting on the remoral head pros- (1997). Direct comparison or contact <.In:as, contact thesis: A study on strain gauge supplied prostheses in liv- ing persons. Acta Orr\/lOp S(\\\"(lIld, SlIppl88. 1-132. and subchondral mineralization in Illunan hip joint s Rvdell, N. (1965). Forces in the hip-joint. Part If: Intravital mens . ..\\\\I\/IJ{ f:'lIlbryol ([kr\/), 195(3), 279-288. . measurements. In R.rvl. Kenedi (i~d.), l3iolllt'cllilUics (jlld","Biomechanics of the Foot and Ankle G, James Sammarco, Ross Todd Hockenbu Introduction Growth of the Foot Kinematics of the Foot Foot and Ankle Motion During Gait Causes of leg Rotation During the Gait Cyde Muscle Action During Gait MotIon of the Tarsal Bones Sublalar Joint Motion Transverse Tarsal Joint Motion Tarsometatarsal and Intertarsal Motion Motion of the Hallux Motion of the Lesser Toes The Medial longitudinal Arch Muscle Control of the Foot Kinetics of the Foot Soft Tissues of the Foot Ankle Joint Biomechanics Kinemaiics Range of Motion Surface Joint Motion Ankle Joint Stability Kinetics of the Ankle Joint Statics Ankle load Distribution Dynamics Effects of Shoewear on Foot\/Ankle Biomechanics Summary References","Introduction found impact on the foot and ankle's shock-abs ing, propulsive, and stabiliZing roles. Clinical c The biomechanics of the fool and ankle arc complex lation of alterations in biomechanical Functio and intricately associated with each olher. The fOOl presented in case studies. Footwear in \\\\Vestern is an integral mechanical part of the lower cxtrcrn- ciety may VaJ'y from a rigid ski boot to a soft ity necessary 1'01' a smooth and stable gaiL The an- casin. These externally restrictive materials ma kle transfers load frolll the lower extremity to the ter normal foot and ankle biomechanics foal and closely inllucnccs foot orientation with the ultimately innucncc the development or s ground. pathological conditions, slich as hallux valgus. The fOOL is comprised of 28 bones (including Growth of the Foot scsamoids) whose motions arc closely inlcn-c1alcd (Fig. 9-1). Besides acting as a structural sllpponing The foot is formcd when the limb buds develop ing the eighth week of gestation. Foot length orplatform capable of withstanding repetitive loads width increases linearly from age 3 to 12 in and age 3 to 15 in boys at an average of 8 to 10 mulliples of body weighl. the fOOL\/ankle complex per year, followed by a plateau in growth (Che also must be able to adjust to different ground sur- al.. 1997). Blais and associales (1956) showcd faces and vat)'ing speeds of IOCOl11CHion. The unique the foot appe\u00abrs to be closer to the adult size a qualities of the 1'001 allow it to be rigid when ncccs- times during normal development of the child Sal)', as in ballet dancing on point, or quile flexible, arc other parts or the limb. On average, at a as in walking barefoot on the sand. The transition )'ear in girls and 18 months in boys, the leng from shock-absorbing platform to rigid lever capa- the foot is one half the length of the respective a ble of forward propulsion occurs wilh cach slep of foot (Fig. 9-3). This situation contrasts with th lhe gail cycle. the femur and tibia, which do not attain their ture length unlil 3 years later in both boys and g The ankle is compriscd of lhrec boncs Ihal form The relativel.\\\\' large size or the fool, then, is im the ankle mortise. This joint complex consists of the tant for providing a broad base on which the ch libiotalar, flbulotalar, and tibiofibular joints (Fig. body is supported. and Lhis base may at tilTlCS c 9-2). The ankle is a hinge joint whose stability de- pensate for the child's lack of muscle strength pends on joint congruency and the medial. lateral, coordination. and syndesmotic ligaments. Kinematics of the Foot This chapter discusses the motions that occur in the foot and ankle during the various phases of gait Gross motion of the foot is complex and oc as well as during extremes or motion. The close in- m'ound three axes and on three planes (Fig. terplay between lower extremity rotation and Fore- Flexion-extension occurs in Lhe sagittal p foot orientation is explained. The ground (foot-to- abduction-adduction occurs in Lhe horizonta floor) reaclion force and dislribulion of forccs on transverse plane, and inversion-eversion occu lhe planlar aspeci of the fOOL are explored. The 10- the coronal or frontal plane. Supination calion of forces as they pass from the tibiofibular pronation are terms commonly used to desc complex into the dome of the talus and then into the positioning of the plantar surface of the foot foot is disclissed. Vve also discuss the roles of liga- occur primarily at the subtalar (talocalcan ments and muscles in the support of the medial lon- joint. During supination the sale faces medi gitudinal arch. Finally, ankle motion and ligamen- and during pronation the sole faces lnter tous stability is outlined. Supination is a combination of inversion, flex and adduction. Pronation is a combinatio A discussion of sophislicated electromyographic eversion, extension, and abduction (Fig. 9-5). activity during walking is not within lhe scope of motion includes Oexion, extension: adduction. this chapter; however, the activity of certain extrin- abduclion. sic and intrinsic muscles is by necessity presented to allow a beller understanding of foot and ankle con- For practical purposes. foot motion can be trol during gait. The moments produced about sidered to be of two distinct types; non-we joints by muscle action and resultant effects on foot and ankle position are detailed. Joint axes and in- stant centers of joint motion are described. Refer Lo Chapler 18 for information aboul the application of biomechanics to gail. Any pathological change in root or ankle struc- ture or motion, however subtle, may have a pro-","Ba\\\\se'K\\\\ \\\"J'\\\"'R,.. Os trigonum Calcaneus Head Phalanges \\\\ Sesamoids Tuberosity MEDIAL VIEW Trochlea Os Metatarsals trigonum Tuberosity calcan~-~~\\\"\\\"\\\"\\\"\\\"'''~ Point or insenion -.;...\u00b7..><'\u00b7:hlea ('ubercle) \/ . 01 the carcaneolibular TuberOSIty Head ligament TU!)fHc!e Groove lor Calcaneus peroneus longus LATERAL VIEW Latera! process Talus -\\\"'- ~~,. Cuneilorms { lateral Medial Middle malleolus Medial Lateral malleolus Tibiofibular articulation r\\\"rsomelalarsal joint (of Lisfranc) HaUul( -Great 100- DORSAL VIEW Top, View of the medial aspect of the foot. Middle. View of the lateral aspect of the foot. Bottom left, Superior view of the foot. Bottom right, Anterior view of the ankle mortise,","La!. Med. beal\\\"ing and weight-bearing. Passive. nOI1-wdgh bearing Illotion may be tested with the patien L Interosseous -~-'-.- 0(~~\u00a5,JI~i ITjbia seated and the foot and ankle hanging free. Subtala membrane motion is evaluated by grasping the tibia with on t hand and inverting and cvcrting the heel with th Fibula ....:. 0 ;f:&;tif~4~~:. other hane!. Abduction and adduction of the fore I\u2022t foot can be tested if the heel is held immobile ll.bl.ofl~biustlaalr .< ...-;&\\\"4.~ Tibiotalar joint Supination and pronation of the forefoot may als I z.:..z.f.,. be tested with the heel fixed, as may flexion and ex ::~.,-:\\\"~r-7: \u2022.\u2022 tension of the tarsometatarsal joints and [Des. ~\/ :R'f1oJ-~- Calcaneus Active, weight-hearing 1TI00ion of the foot differ f from passive motion because the forces produced b Ankle joint complex composed of the tibiotalar, fibulotalar. body weight and by muscle contraction act to stab t and distal tibiofibular joints. lize the joints. Generally, functional active foot mo ~, tion during gait tends to be less than passive foot mo tion. Active subtalar inversion can be demonstrate ~ by viewing heel orientation from behind while askin the patient to raise lip on his 01' her toes. Extel'nal ro f tation of the leg while bearing weight on the foo causes the hed to invert and the forefoot to pronate I therefore raising rhe arch. Rotating the leg internall has rhe opposite effect: it lowers the arch. f LENGTH OF NORMAL FOOT ~' Girls Boys F 30 ,----,----,----,----,----,----,----,----,----, 30 ~ ~;: g .1. !!.28 +-+-+-f-+-+-+-+-+--I I28 I II iI iI I' II I I.! . l 26 0 \/- i 26 +-+--+--+-+-+-++'-+--1 24 +1 -+ 1+1-+1--h-t-:\u00b7,pv';l\\\"\/~\u00b7\u00b7\u00b7\u00b7--4 t 24\\\\ V \u00b7 E::. 22 W-+-~~\u00b7~\u00b7.\u00b7\u00b7\/\u00b7\u00b7.4.+.='1EE::. I22\\\\ I .. i<;V i f I 0 I\u00b7l\/;{. f ~ 20 :& \u00a7 20 i lOX)\u00b7 i ;' \u00a7 18:\/ all\u00b7 I II18 \\\\ I 1,016 t-+--flfC'fJ+'-I-+--T.:-'-...L-j 'I P.'cenmes 16\\\\ i\/..\/'I\/!\u00b7 ~ 1 4 l - l ! f + - + + - + - - 1 \u00b7 \u00b7 \u00b7 \u00b7 \u00b7 \u00b7 \u00b7..\u00b7 \u00b7 \u00b7 \u00b7 5~059~5 I14 +-%ff' f\u2022!lI+-+-+-+--l---'f---H ~ .f. ... 12 \u00b7i 12 H'l-+-+-+-+--l-f---H I 10'O\u00b1jjt\u00b1\u00b1t::\u00b1j lot,\u00b1l=l:\u00b1jj=\u00b1\\\\ jj i o 2 4 6 8 10 12 14 16 18 0 2 4 6 8 10 12 14 1618 ~ Age (years) Age (years) F ~' I. lengths of normal girls' and boys' feet derived from serial measures of 512 children aged 1 to 18 years. Left, Foot length versus age in girls. Note plateau in growth after age 12. Right, Foot length versus age in boys. Note plateau in growth after age 15. Adapted with permission from Blais. M.M.\u2022 Green. W T.. & Anderson. M. (1956). Lengths of the growing (oot. J Bone Joint Surg. 38A. 988.","Dorsiflexionl Eversion! thlllst on the subwlar joill!. In the middle or planlarflexion inversion phase and at push-ofr. the entire lower cxtrcll ~i~lS t(~ reverse and ,:otatc L\u00b7.'(t:nlall~' as ..1he. ~ JOint Sll1lllltancollsl~'II1vcrts (Fig. 9-9). \\\\\\\\illh IIlV of the subtalar joint and supination 01\\\" the fo foot is transformed into a rigid stntclurc cap propulsion. Olerud and Rosendahl (1987) and berg Cl al. (1989a-d) Im\\\"e experiml'ntallv me lhe coupling 01 tibial rot~lliOIl to subtalar m They h<:\\\\ve shown that lhe foot supimues I\\\" fo 0.2 to 0.44\\\" 01\\\" libial external rotation. Foot motion occurs around three axes. Causes of Leg Rotation During the Gait Cycl ~~-------- Malln (1993) has described the coordination o and subtalnr rl'lotion in an ekg::HH model c mitered hingL\\\" (Fig. 9-10). As the tibia interna lales. the subtalar joint evens (pronatcs). COl1 external rotation or the tibia causes in (supination) of the subtalar joint. He attribu internal rotation or th(: lower cx.t1\\\\:l11it~: in stance to the obliquit.\\\\' 01\\\" a general ankk joi (see Ankle Joint l\\\\'totion). According [0 the \\\" oraxis model the ankle joint, the ankle joint angkd downward and postl.'riorly I'rorn Ilk\u00b7dia eral (Fig. 9-1 I). Betau:-ic of the obUquily of th FOOT AND ANKLE MOTION DURING GAIT The gait cycle consists or a stance phase and a swing A, During foot supination the sole faces medially. phase. The stance phase encompasses 62(1'0 of the ing foot pronation the sole faces laterally. gait cycle and the swing phase makes up the re- maining 38%. The stance phase is subdivided into \u2022 heel strike, foot flat, heel rise, push-orr. and toe-off. Swing phase is divided into acceleration, toe clear- ance, and deceleration phases (Fig. 9-6). The part or stance phase spent with both feet on the ground is termed double limb support and occurs through the flrst and last 121'10 of stance phase (Fig. 9-7). N0l111al men have an average gait velocity of 82 m\/min and 58 heel strikes\/min (Waters et aI., 1978). Running is de- fined as a gait speed pasl 201 m\/min. At this speed, double stance disappears and a noat phase develops in which bOlh reet are orr or the ground (Fig. 9-8). During normal walking, the entire lower ex.tremity (including the pelvis, femUl~ and tibia) rotates inter- nally through the first 15% of stance phase. From heel strike through foot flat the subtalar joint everts, tbe foot pronates. and the rorefoot becomes flexible to absorb shock and adapt to irregularities in the\u00b7 ground 11001' surface. The subtalar joint everts in part because the point or contact or the heel is lateral to the center of the ankle joint, thus producing a valgus","l~l=~Kl\\\\\/~~ 17~TlfT~1cr 5l~\/1 II\/\/\/\/II! I Heel stnke Toe ot! Heel st I Stance Phase Stance phase Swing phase <l~--------_~ .~----_~ I! I Heel slnke : Fool flat l~~l-p-\\\"-Sh-O-lI~'-T-o-e-o-I-,-1 I L 0\u00b0\\\" I 15~o I 30~'o I 45~'o 1 60~o I ~I2J~]~~ Double Single limb Double limb support limb support ~~ <1-+ support <1-+ SWing Phase I I IAcceleration [Toe c1em\\\"\\\"e Decelemtion iH~e~ I 70% _~~~~ l 100~,, . . 62 Ii IBII _ '--~~~~~Percent of Walk Cycle 62% of the normal gait cycle is spent in stance phase and Stance phase consists of two periods of double limb su port and one period of single limb support. 38% is spent in swing phase. I &------------------ A Ji A A A A Walking If: :' j: ; Stance ~I6I 5' ,: SWina(?5~o) o 10 20 30 40 50 60 70 80 90 100 Right heel Mid Left heel I.osl\\\"rt~k_e \u2022 + + +'---S-1lr~ke~,-st-a.L:c-eT--T--,-,-F-O-'t-O-'-t Q ' I ' ' I 'Mid Toe Double limb ~:~tl Mid Double limb Right heel RighI twel slrike slance off unsupported strike stance unsupported slnke Running Stance (40%) Swing (30'%) o 10 20 30 40 50 60 70 80 90 100 { ~ftJz~~~~ IBDI'--I _ i i Comparison of walking and running cycles. In the running cycle, stance phase decreases, 9p \u2022 __fS_lWo_aint__ph_ah_sae_se_dine_vc_er_leo_ap_sse_:S_'_d_O_U_b_l_e_l_im_b_S_U_P_P_O_rl_d_iS_a_p_p_e_a_rs_,_a_n_d_a_d_o_U_b_l_e_l_im_b_U_n_s_u_p_p_o_r_te_d_o_r 1","..Heel contacl .. ..Toe-off Heel contact Ankle _. rotation i :! ' Stance phase _: !.......-:-- ,6~T , I .:t; .... FOOl immobile ....: Subia la, ~_.'-_..__ A B rolation :- f,' \u00b0 m -----',._L_~_~..-----,----;c;;~' _._~ I ~W W 100 lI Percent of Walking Cycle I I I I I Ankle motion and subtalar rotation during normal walking. c o Maximal subtalar eversion occurs at foot flat in early stance phase. Maximum subtalar inversion occurs at toe-off. \u2022 joint axis, the leg internally rotates with ankle dorsi~ Mitered hinge model of leg, ankle, and subtalar mo flexion and externally rotates with ankle plal1larflex- A. Outward rotation of the upper stick causes inwa ion. Additional mechanisms by which leg external ro- tion of the lower stick. 8. Inward rotation of the up tation occurs during late stance include the swing of stick causes outward rotation of the lower stick. C. the opposite leg that causes external rotation of the nal tibial rotation causes supination of the foot. O. planted leg and the obliquity of the metatarsal break tibial rotation causes pronation of the foot. (Fig. 9- I 2). The metatarsal break is an oblique axis of 50 to 70\\\" with respect to the long axis of the [oat Number of formed by the centers of rotation of the metatar- specimens sophalangeal joints. With push-off. the foot and lower extremity externally rotate with respect to the 20 sagittal plane because of this oblique axis. r15 r MUSCLE ACTION DURING GAIT I Although the motions of the foot and ankle during {10' the walking cycle OCClIr primarily as a result of the passive constraints of joints and ligaments. elec- 74 78 82 86 90 94 trom.yography has shown that rnuscle activity does Angle (degrees) occur during normal gait (Fig. 9-13). At heel strike, the pretibial musculature fires eccentrically to slow Variations in the angle between the midline of the down the descent of the forefoot and prevent a [oat and the empirical axis of the ankle. The axis is angle slap. At midstance, the calf musculature contracls obliquely and inferoJaterally 82\u00b0. The histogram sho to slow down the Fonvard movement of the body variability among specimens. over the foot and prevent a crouch gait. The intrin- sics also contract during midstance to toe-off to aid in rigidity of the forefoot. Toe-off is primarily a pas- sive event. The pretibial musculature again con- tracts during swing phase to ensure (hat the fOOl clears the Ooor during swing~lhrough.","Metatarsal version and eversion. The sublalar joint is respo break sible along with the transverse tarsal joint (consis ing of the talonavicular and calcaneocuboid joint for transforming tibial rotation into forefo supination and pronation. Because the ankle Joi is to some degree a single-axis joint. subtalar m tion reduces the rOLaloly' stresses to the ankle join Congenitally blocked motion of the subtalar joi may result in the formation of a ball-aod-sock ankle as a result of the increased rota1011' stress the joint. Manter (1941) determined Ihe subtal axis of rotation to be oriented upward at an ang of 42\\\" fmm the horizontal and medially 16\\\" fro the midline (Fig. 9-14). The sublalar facets resem ble segments of a \\\"spiral of Archimedes,\\\" a righ handed screw in the right foot, so that the calc neus actually translates anteriorly along t subralar axis as it rotates clockwise during the m tion of subtalar inversion (Fig. 9-15). A\\\\\u00b7erage su talar motion is 20 to 30\u00b0 inversion and 5 to 1 eversion. Functional subtalar joint motion duri gait is 10 to 15\u00b0. During the gait cycle, the he strikes the ground in slight inversion, followed rapid eversion to a maXimUI11 of 5 to 10\u00b0 at 10% the gait cycle (Fig. 9-9) (Sarrafian, 1993a,b). Transverse Tarsal Joint Motion The transverse tarsal joint, Chopart's joint, consists the talonavicular joint and calcaneocuboid joi Manier (1941) described two axes of motion in t I II I Muscle activity 1__ Slance -.1.,Sw;n9....1 $ I phase I phase I The muscles of the lower extremity are more ac- I 1I live dudng nmning. The gluteus maximus and ham- strings arc active in midstance through toe-off and Pretibial muscle -I NjWl~----.......INI lVNm'fM\/'lir increase their activity 30 to 500\/0 1O decelerate the ,;.: stance phase limb. Dorsillexors of the foot and an- Triceps (calf) .L--..\/MlWWJW'J,IIlWil,J----...L kle are active in 700\/0 of the running cycle. The in- I trinsics, plantar flexors, and peroneals are impor- tant stabilizers of the plantar surface and hindfoot 1 during the foot nat phase (Aclelaar, 1986). '\\\"\\\"\\\"-1 JlFoot I I MOTION OF THE TARSAL BONES li Subtalar Joint Motion Inilial Lift Initial The joint between the talus and calcaneus is lermed the subtalar joinl. Its complex motion in floor off floor three planes produces the motions of supination contact and pronation, c1inicnll.y referred to as subtalar in- contact Schematic phasic activity of leg and foot muscles during normal gait."]
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