Chapter 8. The Lower Extremity: The Knee, Ankle, and Foot

At the conclusion of this chapter, the student should be able to:

• 1. Name, locate, and describe the structure and ligamentous reinforcements of the articulations of the knee, ankle, and foot.
• 2. Name and demonstrate the movements possible in the joints of the knee, ankle, and foot, regardless of starting position.
• 3. Name and locate the muscles and muscle groups of the knee, ankle, and foot, and name their primary actions as agonists, stabilizers, neutralizers, or antagonists.
• 4. Analyze the fundamental movements of the lower leg and foot with respect to joint and muscle actions.
• 5. Describe the common injuries of the leg, knee, and ankle.
• 6. Perform an anatomical analysis of the lower extremity in a motor skill.

The knee joint is the largest and most complex joint in the human body. It is a masterpiece of anatomical engineering. Placed midway down each supporting column of the body, it is subject to severe stresses and strains in its combined functions of weight bearing and locomotion. To take care of the weight-bearing stresses, it has massive condyles; to facilitate locomotion it has a wide range of motion; to resist the lateral stresses due to the tremendous lever effect of the long femur and tibia, it is reinforced at the sides by strong ligaments; to combat the downward pull of gravity and to meet the demands of such violent locomotor activities as running and jumping, it is provided with powerful musculature. It would be difficult, indeed, to find a mechanism better adapted for meeting the combined requirements of stability and mobility than the knee joint.

Structure

Although the knee is classified as a hinge joint, its bony structure resembles two condyloid or ovoid joints lying side by side, yet not quite parallel (Figure 8.1). The lateral flexion permitted in a single ovoid joint is not possible in the knee joint because of the presence of the second condyle. The two rockerlike condyles of the femur rest on the two slightly concave areas on the top of the tibia’s broad head. These articular surfaces of the tibia are separated by a roughened area, called the intercondyloid eminence, which terminates both anteriorly and posteriorly in a slight hollow but rises at the center to form two small tubercles like miniature twin mountain peaks (Figure 8.2). During knee extension, the intercondyloid tubercles enter the intercondyloid fossa of the femur. The medial articular surface of the tibia is oval; the lateral is smaller and more nearly round. Each is overlaid by a somewhat crescent-shaped fibrocartilage, known as a semilunar cartilage, or meniscus.

The lower end of the femur terminates in the two rockerlike condyles already mentioned. The lateral condyle is broader and more prominent than the medial. The medial condyle projects downward farther than the lateral. This is evident, however, only when a disarticulated femur is held vertically. In its normal position in the body, the femur slants inward from above. This slant is known as the obliquity of the femoral shaft. Observation of the mounted skeleton will show that the downward projection of the medial condyle compensates for the obliquity of the femoral shaft.

Another interesting feature of the condyles is that they are not quite parallel. Whereas the lateral condyle lies in the sagittal plane, the medial condyle slants slightly medially from front to back. This is an important factor in the movements of the knee.

Anteriorly, the two condyles are continuous with the smooth, slightly concave surface of the patellar facet for the articulation of the patella. The patella, or kneecap, is a large sesamoid bone located slightly above and in front of the knee joint. It is held in place by the quadriceps tendon above, by the patellar ligament below, and by the intervening fibers that form a pocket for the patella (Figure 8.3).

The articular cavity is enclosed within a loose membranous capsule that lies under the patella and folds around each condyle but excludes the intercondyloid tubercles and cruciate ligaments. It is supplemented by expansions from the fascia lata, iliotibial tract, and various tendons. The oblique popliteal ligament covers the posterior surface of the joint completely, shielding the cruciate ligaments and other structures not enclosed within the capsule.

The synovial membrane of the knee joint is the most extensive of any in the body. It folds in and around the joint in a manner far too complicated to attempt to describe here. There are numerous bursae in the vicinity of the knee joint. The largest and most important of these bursae are the prepatellar, infrapatellar, and suprapatellar bursae.

Menisci

The menisci (Figure 8.4) are circular rims of fibrocartilage situated on the articular surfaces of the head of the tibia. They are relatively thick at their peripheral borders but taper to a thin edge at their inner circumferences. Thus they deepen the articular facets of the tibia and, at the same time, serve in a shock-absorbing capacity. The inner edges are free, but the peripheral borders are attached loosely to the rim of the head of the tibia by fibers from the inner surface of the capsule.

The lateral meniscus forms an incomplete circle, conforming closely to the nearly round articular facet. Its anterior and posterior horns, which almost meet at the center of the joint, are attached to the intercondyloid eminence.

The medial cartilage is shaped like a large letter C, broader toward the rear than in front. Its anterior horn tapers off to a thin strand attached to the anterior intercondyloid fossa. It is not as freely movable as the lateral cartilage because of its secure anchorage to the medial collateral ligament at the medial side of the knee and the semimembranosus muscle posteriorly. Largely because of these points of attachment, the medial cartilage is more frequently injured than the lateral.

Patellofemoral Joint

The patella is the largest sesamoid bone in the body. Located on the anterior side of the femur at the knee joint, the patella has several functions. The depth of the patella serves as a pulley to increase the angle of pull of the quadriceps muscles. Because all four of these muscles converge at the patella, through the quadriceps tendon, the patella functions to direct the force of the quadriceps through the patellar ligament.

The posterior surface of the patella articulates with the femur at the patellar surface, or patellar groove. As the knee flexes, the patella slides in this groove in a motion referred to as patellar tracking. As the quadriceps muscles exert a pull on the patella, the patella is pulled against the femur, increasing both contact area and contact forces. As the patella tracks downward over the femur during knee flexion, it will tilt inferiorly and slightly medially, returning during extension (Patel et al. 2003).

Ligaments of the Knee

Patellar Ligament (Figure 8.3)

This is a strong, flat ligament connecting the lower margin of the patella with the tuberosity of the tibia. Passing over the front of the patella, the superficial fibers are continuations of the central fibers of the quadriceps femoris tendon.

Medial Collateral Ligament (Figures 8.3a and 8.5)

This is a broad, flat, membranous band on the medial side of the joint. It is attached above to the medial epicondyle of the femur below the adductor tubercle and below to the medial condyle of the tibia. It is firmly attached to the medial meniscus. This fact should be noted because of its significance in knee injuries. It serves to check extension and to prevent motion laterally.

Lateral Collateral Ligament (Figures 8.3 and 8.5)

This is a strong, rounded cord attached above to the back of the lateral epicondyle of the femur and below to the lateral surface of the head of the fibula. It serves to check extension and to prevent motion medially.

Oblique Popliteal Ligament (Figure 8.3b)

This is a broad, flat ligament covering the back of the knee joint. It is attached above to the upper margin of the intercondyloid fossa and posterior surface of the femur and below to the posterior margin of the head of the tibia. Medially it blends with the tendon of the semimembranosus muscle, and laterally with the lateral head of the gastrocnemius. It too protects against hyperextension.

The Cruciate Ligaments (Figure 8.5)

These are two strong, cordlike ligaments situated within the knee joint, although not enclosed within the joint capsule. They are called cruciate because they cross each other. They are further designated anterior and posterior, according to their attachments to the tibia. They serve to check certain movements at the knee joint. They limit extension and prevent rotation in the extended position. They also check the forward and backward sliding of the femur on the tibia, thus safeguarding the anteroposterior stability of the knee.

Anterior Cruciate Ligament (Figure 8.5)

This passes upward and backward from the anterior intercondyloid fossa of the tibia to the back part of the medial surface of the lateral condyle of the femur.

Posterior Cruciate Ligament (Figure 8.5)

This is a shorter and stronger ligament than the anterior. It passes upward and forward from the posterior intercondyloid fossa of the tibia to the lateral and front part of the medial condyle of the femur.

Transverse Ligament (Figure 8.4)

This is a short, slender, cordlike ligament connecting the anterior convex margin of the lateral meniscus to the anterior end of the medial meniscus.

The Iliotibial Tract (Figures 7.18 and 7.19)

The iliotibial tract is said to act like a tense ligament that connects the iliac crest with the lateral femoral condyle and the lateral tubercle of the tibia. At the knee joint the tract serves as a stabilizing ligament between the lateral condyle of the femur and the tibia.

Movements

The movements that occur at the knee joint are primarily flexion and extension. A slight amount of rotation can take place when the knee is in the flexed position and the foot is not supporting the weight or during the initial stages of flexion and the final stages of extension (Figure 8.6).

Flexion and Extension

The movements of flexion and extension at the knee are not as simple as those of a true hinge joint. This can be demonstrated in the classroom by holding a disarticulated femur and tibia together in a position of extension and then, holding the tibia stationary, flexing the femur on the tibia as though the individual were assuming a squat or sitting position. If no other adjustment is made, the femoral condyles will roll back completely off the top of the tibia. What prevents this from happening in real life is the fact that, as the condyles roll backward, they simultaneously glide forward and thus remain in contact with the menisci throughout each phase of the movement. In addition, the anterior cruciate becomes taut and prevents further backward translation. Conversely, when the femur extends on the tibia, the forward roll of the femoral condyles is accompanied by both a backward glide and the pull of the posterior cruciate to help prevent forward dislocation.

Because the femoral condyles are not quite parallel and the medial condyle is slightly longer, a slight degree of rotation occurs during the initial phase of flexion and the final phase of extension. This can be seen readily on the living subject who stands with the knees slightly flexed and then extends them completely. The patellae turn slightly medialward, indicating slight inward rotation of the thighs. Because of the inequality of the two condyles, the medial condyle continues to roll forward after the lateral condyle has ceased its movement. The inward rotation of the femur that accompanies the completion of extension is commonly known as the “locking” or “screw home” mechanism of the knees. In persons who tend to hyperextend their knees habitually, the rotation is more pronounced.

When the leg is flexed or extended in a non-weight-bearing position, the tibia rotates on the femur, instead of vice versa. The final phase of extension is accompanied by slight outward rotation of the tibia. At the beginning of flexion the tibia rotates inward until the midposition is attained.

The rotation that occurs in the final stage of extension and the initial phase of flexion is an inherent part of these movements and should not be confused with the voluntary rotation that can be performed when the leg is not bearing weight and the knee is in a flexed position.

Inward and Outward Rotation in the Flexed Position

In spite of the fact that the knee joint is classified as a hinge joint, its condylar structure accommodates movement other than just flexion and extension under certain conditions. When the leg has been flexed at the knee, the collateral ligaments become slack and it is possible to rotate the leg on the thigh through a total range of about 50 degrees. This can occur, however, only when the leg is not bearing the body weight. It is impossible, for instance, to rotate either the leg or the thigh in this manner when the body is in a stooping position. A good way to demonstrate rotation of the tibia is to sit on a chair with the heel resting lightly on the floor. In this position, with the knee and thigh held motionless, the foot should be turned first in and then out. The action will be that of inward and outward rotation of the tibia. The movement taking place within the foot itself should be discounted. Taut collateral and cruciate ligaments prevent rotation when the leg is extended at the knee, either in a weight-bearing or non-weight-bearing position. Inward or outward movements of the foot in the extended position are due to rotation at the hip joint.

Location

The muscles acting on the knee joint are classified as anterior or posterior according to the relation of their distal tendons to the transverse axis of the joint.

Characteristics and Functions of Individual Muscles

Quadriceps Femoris Group

This group (Figures 8.3, 8.7, and 8.8) consists of the rectus femoris and the vasti: vastus intermedius, vastus lateralis, and vastus medialis. Of these, only the rectus femoris, the most superficial of the four, crosses the hip joint. The vastus intermedius lies posterior to the rectus and is completely covered by it. The distal portions of the four muscles unite to form a single broad, flat tendon that attaches to the base of the patella, the base being the upper border. The patellar ligament connecting the patella with the tuberosity of the tibia is a vital part of the quadriceps femoris. Actually, the patella is a sesamoid bone encased within the quadriceps tendon, with the patellar ligament being but a continuation of this and the tibial tuberosity the true distal point of attachment of the muscle group. All four muscles extend the leg at the knee joint and function as a unit in doing so.

The vastus lateralis and vastus medialis, with their fibers converging toward the patella, act with the vastus intermedius and rectus femoris, with their longitudinal approach, to steady the knee joint in weight-bearing positions and to maintain a balanced tension on the patella. There is very little activity from these muscles, however, in relaxed standing. Because the three vasti are one-joint muscles, they are powerful knee extensors, regardless of the position of the hip joint. Their greatest activity is during the last part of knee extension. The vastus medialis is the most active of the three throughout the greatest range of knee extension. Its lower portion is also important in preventing lateral dislocation of the patella. When the knee is fully extended, static contraction of the quadriceps serves to pull up or “set” the patella, a mild exercise used in rehabilitation of the injured knee. This pull on the patella is not directly vertical but is at an angle to the femur. The pull angle of the quadriceps is commonly referred to as the Q angle. This angle is measured as shown in Figure 8.9, at the intersection of lines drawn from the center of the patella to the anterior superior iliac spine and from the tibial tuberosity to the center of the patella. Normal Q angles range from 8 degrees to 17 degrees, usually slightly higher in females than in males. The influence of Q angle on patellofemoral problems is still a matter of debate. Research on this topic has produced conflicting results, and the final word has yet to be written (Hand and Spalding 2004; Heiderscheit et al. 2000; Mizuno et al. 2001).

The two-joint rectus femoris (also listed with the hip muscles) is of bipenniform structure with all except the lowest fibers slanting obliquely downward and sideward from the central tendon and the lowest fibers being approximately vertical (see Figure 8.7). The upper three-quarters of the muscle consists of the muscle fibers, with the last quarter, down to the base of the patella, being the muscle’s distal tendon. The entire muscle contracts regardless of whether it is producing movement at the hip joint or knee joint. It is most effective at the knee joint when the hip joint is extended. The muscle may be palpated on the central-anterior surface of the thigh.

The majority of the vastus lateralis fibers slant downward and medialward to the tendon. The muscle may be palpated on the anterolateral aspect of the thigh, lateral to the rectus femoris.

Most of the fibers of the vastus medialis slant downward and lateralward to the tendon, with the lowest ones almost horizontal in direction. If the lateralis and medialis were looked upon as one muscle, it would be considered to be of bipenniform construction, with the fibers slanting in direct opposition to those of the rectus femoris. The fleshy part of both the medialis and lateralis extends down almost to the level of the base of the patella. The vastus medialis may be palpated on the anteromedial aspect of the lower third of the thigh, medial to the rectus femoris.

Hamstring Group (Also Listed with the Hip Muscles)

The hamstrings (Figures 8.10 and 8.11), so named from their large, cordlike tendons behind the knee joint, consist of the biceps femoris, semimembranosus, and semitendinosus muscles. Although the biceps femoris constitutes the lateral hamstring, its long head lies approximately along the midline of the posterior aspect of the thigh, as far down as the popliteal space. The long head comes from the tuberosity of the ischium, and the short head originates from the linea aspera on the posterior surface of the thigh. The two join at the distal tendon close to the lateral condyle of the femur, not far above the tendon’s attachment to the head of the fibula. It is an important flexor of the knee. When the knee is flexed and not bearing weight, the biceps femoris can rotate the lower leg outward. Its tendon may be palpated behind the knee on its lateral aspect. The long head is fusiform in construction; the short head is penniform.

The semimembranosus and semitendinosus constitute the medial hamstrings. The former lies deeper than the latter and attaches higher on the tibia. The semitendinosus is attached to the medial surface of the tibia, below the head, just below the attachment of the gracilis and behind that of the sartorius. Like the biceps femoris, they flex the knee joint. Unlike the biceps femoris, the semimembranosus and semitendinosus medially rotate the unweighted and flexed tibia. The semitendinosus may be palpated on the medial aspect of the posterior surface of the knee. The tendon of the semimembranosus is almost impossible to palpate successfully because it is shorter than its partner and is partially covered by the latter, as well as by the gracilis tendon.

Nearly everyone is familiar with the limiting effect of the hamstrings. Many experience difficulty in touching the toes with the fingers without bending the knees and in sitting erect on the floor with the legs extended straight forward because the hamstrings are frequently not long enough to permit such extreme stretching at the hips and knees simultaneously.

Sartorius (Also Listed with the Hip Muscles)

This is a long, slender, ribbonlike muscle (see Figure 8.7) superficially located and directed obliquely downward and medialward across the front of the thigh. On its way to its distal attachment, it curves around behind the bulge of the medial condyles in such a way that its line of pull is posterior to the axis of the knee joint. Thus, in spite of the fact that at least two-thirds of the muscle, including both its proximal and distal attachments, lies on the anterior aspect of the lower extremity, its action at the knee joint is generally flexion, not extension. It also assists in inward rotation of the tibia when the leg is flexed at the knee and is not bearing weight. The line of pull of the sartorius is determined by the direction of its distal tendon, between the latter’s point of contact with the medial condyle of the tibia and its attachment to the upper anteromedial surface of the tibial shaft, almost as far forward as the anterior crest. It may be palpated at the anterior superior iliac spine, as well as along its entire length, where it is clearly visible on a thin, well-muscled subject.

Gracilis (Also Listed with the Hip Muscles)

This is a long, slender muscle (see Figures 8.8 and 8.11) situated on the medial aspect of the thigh. Its action at the knee joint is flexion. It also is slightly active in inward rotation of the tibia when the knee is in a flexed position and the foot is not bearing weight. It may be palpated on the medial aspect of the posterior surface of the knee, anterior to the semitendinosus tendon but close to it.

Popliteus

This muscle (see Figure 8.11) rotates the tibia inward and helps flex the knee. In structure and function it resembles the pronator teres muscle of the elbow. In a subject who is standing, it “unlocks” the knee joint preliminary to flexion. It also helps protect and stabilize the knee joint from forward dislocation of the femur when a squatting position is assumed and maintained. During walking, it is active throughout most of the weight-bearing phase (Basmajian and DeLuca 1985).

Gastrocnemius (Also Listed with the Ankle Muscles)

This large calf muscle (see Figure 8.23), although primarily a muscle of the ankle joint, has an important function at the knee joint. It is in a position to help flex the knee and does so when the leg is not bearing weight. It also functions at the knee as a posterior ligament to protect the joint in movements involving violent extension, as in running and jumping.

When the foot is fixed in weight bearing, the gastrocnemius can help maintain knee extension. It does this when the hip and knee are in strong extension and when plantar flexion of the ankle is inhibited, such as when the line of gravity passes in front of the knee and ankle joints. Under these circumstances, the gastrocnemius is able to pull back and down on the femoral condyles, thus contributing to knee extension. Its activity in “relaxed standing at ease” was found in three-fourths of subjects tested barefooted. The wearing of high heels increased the frequency of subjects whose muscles were active. The muscle is easy to palpate, including both the muscle belly in the calf and the tendon behind the ankle.

Flexion

The knee joint has five important flexors, namely the three hamstring muscles (biceps femoris, semimembranosus, and semitendinosus), the sartorius, and the gracilis; the latter is especially important during the early part of flexion, provided that the hip is not flexing simultaneously. Two additional muscles that help with flexion are the popliteus and gastrocnemius.

It should be remembered that when the weight is borne by the feet and the knees are allowed to flex, as in stooping, the knee flexors are not responsible for the movement. The flexion is produced by the force of gravity and is controlled by the extensor muscles that are contracting eccentrically, that is, in lengthening contraction.

The three adductors have also been shown to be active in most children during flexion and extension of the knee with or without external resistance. They were also active under the same conditions in most adults during knee flexion, but activity of these muscles during extension occurred only when resistance was applied (Basmajian and DeLuca 1985).

Extension

This action is performed by the four muscles that make up the quadriceps femoris group: the rectus femoris, the vastus intermedius, the vastus lateralis, and the vastus medialis.

Outward Rotation of the Tibia

This action is performed by the biceps femoris. It can occur only when the knee is flexed in a non-weight-bearing situation.

Inward Rotation of the Tibia

This action is performed chiefly by the semimembranosus, semitendinosus, and popliteus, with possible help from the gracilis and sartorius. As with outward rotation, it can occur only when the knee is flexed and the foot is not bearing weight.

The foot has two functions of great importance: support and propulsion. In studying the structure of the foot, one should keep these functions in mind. Only by seeing the foot in terms of the combined static and dynamic demands made upon it can one fully appreciate its intricate mechanism.

The foot is united with the leg at the ankle joint. Within the foot itself are the seven tarsal bones. Two of the joints in this region are of sufficient importance to the kinesiologist to merit special attention. These are the subtalar and midtarsal joints, the latter including the talonavicular and calcaneocuboid articulations. The movements within the foot occur mainly at these two joints.

The structure of the ankle, tarsal joints, and toes will be described separately, but the muscles of these three regions will be discussed together because many of them act on more than one joint.

Structure of the Ankle

The ankle (talocrural) joint (Figures 8.12, 8.13, and 8.14) is a hinge joint. It is formed by the articulation of the talus (astragalus) with the malleoli of the tibia and the fibula. The malleolus of the fibula lies more posterior and extends more distally than that of the tibia. The malleoli of the tibia and fibula, bound together by the transverse tibiofibular ligament, the anterior and posterior ligaments of the lateral malleolus, and the interossei, constitute a mortise into which the upper, rounded portion of the talus fits. The transverse tibiofibular ligament secures the lateral and medial malleoli and the back surface of the talus. The ankle joint is surrounded by a thin, membranous capsule that is thicker on the medial side of the joint. In the back it is a thin mesh of membranous tissue and is not continuous, as are most capsules. It is reinforced by several strong ligaments.

Ligamentous Reinforcement

The medial side of the ankle joint is protected by five strong ligamentous bands (see Figure 8.13), four of them connecting the medial malleolus of the tibia with the posterior tarsal bones, the calcaneus, talus, and navicular. These four ligaments are known collectively as the deltoid ligament. Individually they are the calcaneotibial, the anterior talotibial, the tibionavicular, and the posterior talotibial ligaments. The fifth band (plantar calcaneonavicular) provides a horizontal connection between the navicular bone and the sustentaculum tali projection on the medial aspect of the calcaneus. It is also known as the spring ligament.

The lateral side of the ankle is reinforced (see Figure 8.14) by three ligaments collectively called the lateral collateral ligament. These connect the lateral malleolus with the upper lateral aspect of the calcaneus and with anterior and posterior portions of the talus. The components of the lateral collateral ligament are named the calcaneofibular and anterior and posterior talofibular ligaments, respectively. The lateral ligaments are weaker than the medial ligaments, and the anterior talofibular ligament is the weakest of all. Inspection of Figures 8.13 and 8.14 gives one the impression that the lateral side of the ankle is less protected than the medial. These facts help explain the high incidence of lateral ankle sprains.

Structure of the Foot

The foot as a whole (Figures 8.15 and 8.16) is usually described as an elastic arched structure, the keystone of the arch being the talus. This bone has several marks of distinction. Aside from being the connecting link between the foot and the leg, it is distinguished by having no muscles attached to it and by receiving and transmitting the weight of the entire body (with the exception of the foot itself), a function that requires great strength and firm support.

The foot has two arches, a longitudinal and a transverse. The longitudinal arch extends from the heel to the heads of the five metatarsals. It is sometimes described as being made up of a medial and a lateral component. The lateral component includes the calcaneus, cuboid, and fourth and fifth metatarsals (Figure 8.16a). The medial component consists of the calcaneus, talus, navicular, three cuneiforms, and the three medial metatarsals (Figure 8.16b). The lateral component has a nearly flat contour and lacks mobility; hence, it is better adapted to the function of support. The medial component, with its greater flexibility and its curving arch, is adapted to the function of shock absorption, so important in all forms of locomotion. The longitudinal arch is strongly supported by the plantar fascia. The fascia is a relatively strong sheet of tissue attached to the calcaneous, each of the metatarsal heads, and several of the tarsal bones (cuneiform and navicular) as well as the base of the first and fifth metatarsals. The plantar fascia helps maintain the arch of the foot. It also transmits forces from the Achilles tendon to the forefoot. These loads can be as much as 92 percent of the body weight (Cheung et al. 2004; Erdemir et al. 2004). Contrary to popular opinion, the height of the longitudinal arch is not indicative of the strength of the arch. Thus, a low arch is not necessarily a weak one, provided it is not associated with a pronated (i.e., abducted and everted) foot.

The transverse arch is the side-to-side concavity on the underside of the foot formed by the anterior tarsal bones and the metatarsals. The anterior boundary of this arch under the metatarsal heads is known as the metatarsal arch. There is some disagreement as to whether this should be called an arch, because it flattens completely when bearing weight. The metatarsal arch exists, therefore, only in non-weight-bearing situations.

The toes, especially the large and powerful “big toes,” are largely responsible for propulsion. They provide the push-off at the end of the step. Their use in locomotion is directly proportional to the vigor and speed of the walk or run.

The strength and elasticity of the foot, which is comprised of twenty-six bones, are due largely to the ligaments that bind the bones together and to the muscles that work to preserve the balance of the foot. Thus, both ligaments and muscles share the responsibility for maintaining the integrity of the feet.

Subtalar Joint (Talocalcaneal)

This is the joint (Figure 8.17) between the underside of the talus and the upper and anterior aspects of the calcaneus, or heel, bone. It is reinforced by four small talocalcaneal ligaments. A fifth ligament, the plantar calcaneonavicular, is probably the most important of all. It is a broad, thick ligament that connects the sustentaculum tali projection of the calcaneus with the underside of the navicular bone. It passes under the talus and aids in supporting it. It is actually part of the subtalar joint, because it contains a fibrocartilaginous facet that is lined with synovial membrane. This is commonly called the spring ligament because of the yellow elastic fibers that give it its elasticity. The importance of this ligament can be readily understood when one remembers that the talus receives the weight of the entire body. The shock-absorbing function of this elastic support is obvious. It is probably equally obvious that excessive prolonged pressure on this ligament through improper use of the feet will cause it to stretch permanently and thus result in a lowered arch.

Unfortunately, Figure 8.17b gives a somewhat misleading picture of this ligament. Although it looks like a cord-shaped ligament on the medial aspect of the ankle, the part that shows in the picture is actually just the medial border of a broad ligament that extends beneath the head of the talus, like a taut hammock.

Midtarsal Joint (Transverse Tarsal; Chopart’s Joint)

The midtarsal joint consists of two articulations, the lateral one being the calcaneocuboid joint and the medial one the talonavicular. Viewed from above, the continuous line of articulation—the talonavicular and calcaneocuboid—forms a somewhat shallow letter S (Figures 8.15b and 8.18). The talonavicular joint is a modified ball-and-socket joint and permits somewhat restricted movements about three axes. The calcaneocuboid joint is nonaxial and permits only slight gliding motions. These seem to be supplementary or secondary to the freer motions of the talonavicular joint. Several ligaments reinforce these joints, but the ones that give the most support are the long and short plantar (calcaneocuboid) ligaments. These are both wide, thick ligaments of great strength.

Tarsometatarsal Joints

These joints (Figures 8.15 and 8.19) are nonaxial, with the possible exception of the great toe joint, which looks slightly like a saddle joint. The movements are of a gliding nature that resembles a restricted form of flexion, extension, abduction, and adduction.

Intermetatarsal Joints

These joints (see Figures 8.14 and 8.19) include two sets of side-by-side articulations, those between the bases and those between the heads of the metatarsal bones. They are all nonaxial joints. The articulations between the heads of the metatarsal bones are an important part of the metatarsal arch. The total result of the movements occurring there is a spreading or flattening of the arch when the weight is on it and a return to its plantar concavity when the weight is taken off it.

Metatarsophalangeal Joints

These joints (see Figures 8.15 and 8.19) may best be described as a modified form of condyloid joint. The joint of the great toe differs from the others in that it is larger and has two sesamoid bones beneath it.

Interphalangeal Joints

As is true of the fingers, these are all hinge joints (see Figures 8.15 and 8.19).

Movements of the Foot at the Ankle, Tarsal, and Toe Joints

Ankle Joint

The movements of the ankle joint occur about an axis that is usually described as bilateral but is actually slightly oblique, as evidenced by the slightly posterior position of the lateral malleolus relative to the medial. This is of minor significance, but it explains the tendency of the foot to turn out when it is fully dorsiflexed and to turn in when fully plantar flexed (Figure 8.20).

Dorsiflexion (Flexion)

A forward upward movement of the foot in the sagittal plane, so that the dorsal surface of the foot approaches the anterior surface of the leg.

Plantar Flexion (Extension)

A forward downward movement of the foot in the sagittal plane, so that the dorsal surface of the foot moves away from the anterior surface of the leg.

Tarsal Joints

The movements that take place at the midtarsal, subtalar, and other tarsal joints occur together and are usually closely related to the ankle joint movements. Except for the talonavicular joint, which belongs to the ball-and-socket category, they are all nonaxial joints and therefore permit only slight gliding movements (Figure 8.20).

Dorsiflexion

Slight decrease in convexity of dorsal surface and in concavity of plantar surface of tarsal region. Accompanies dorsiflexion of ankle.

Plantar Flexion

Increase in convexity of dorsal surface and in concavity of plantar surface of tarsal region. Accompanies plantar flexion of ankle.

Inversion and Adduction (Supination)

A lifting of the medial border of the arch combined with a medial bending of the front of the foot.

Eversion and Abduction (Pronation)

A slight raising of the lateral border of the foot combined with a slight lateral bending of the front of the foot.

Tarsometatarsal and Intermetatarsal Joints

These joints have a slight gliding motion. The first metatarsal bone has a slightly greater degree of motion at these joints than do the other metatarsals because of the absence of any ligament between its base and the base of the second metatarsal.

Metatarsophalangeal Joints

Flexion, extension, and limited abduction and adduction.

Interphalangeal Joints

Flexion and extension; also hyperextension, especially of the great toe.

Location

Eleven of the twenty-two muscles of the ankle and foot are intrinsic; that is, they are located entirely within the foot. The other eleven are extrinsic; they have distal tendon attachments on the foot but are otherwise located outside it (Table 8.1). A twelveth extrinsic muscle, the plantaris, has been omitted because it is a vestige often absent in human beings. When present it assists the ankle extensor muscles.

Characteristics and Functions of Individual Muscles

Tibialis Anterior

This muscle (Figure 8.21a) lies along the full length of the anterior surface of the tibia from the lateral condyle down to the medial aspect of the tarsometatarsal region. Approximately one-half to two-thirds of the way down the leg it becomes tendinous. The tendon passes in front of the medial malleolus on its way to the first cuneiform. The muscle dorsiflexes the ankle and foot, and supinates (inverts and adducts) the tarsal joints when the foot is dorsiflexed. In EMG studies it was found that one-half the subjects in free standing had activity in the tibialis anterior that went away when the subjects leaned forward. The muscle is also active during the initial contact phase of walking, allowing the foot to be lowered to the ground in a controlled manner. The muscle may be palpated on the anterior surface of the leg just lateral to the tibia.

Extensor Digitorum Longus

This muscle (Figures 8.21b and 8.22) extends the four lesser toes. It also dorsiflexes both the ankle and the tarsal joints and helps evert and abduct the latter. It is a penniform muscle, situated lateral to the tibialis anterior muscle in the upper part of the leg and lateral to the extensor hallucis longus in the lower part. Just in front of the ankle joint the tendon divides into four tendons, one for each of the lesser toes. The muscle may be palpated on the anterior surface of the ankle and the dorsal surface of the foot, lateral to the tendon of the extensor hallucis longus.

Extensor Hallucis Longus

This muscle (see Figure 8.21a) extends and hyperextends the great toe. It also dorsiflexes the ankle and the tarsal joints. Like the preceding muscle, it is penniform in structure. Its upper portion lies beneath the tibialis anterior and extensor digitorum longus, but about halfway down the leg the tendon emerges between these two muscles, thus becoming superficial. After it reaches the ankle, the tendon slants medially across the dorsal surface of the foot to the top of the great toe. It may be palpated on the dorsal surface of the foot and great toe.

Peroneus Tertius

This muscle (see Figure 8.22) dorsiflexes and pronates (everts and abducts) the tarsal joints and dorsiflexes the ankle. It is a small muscle that lies lateral to the extensor digitorum longus, sometimes described as the fifth tendon of the latter muscle. It may be palpated on the dorsal surface of the foot close to the base of the fifth metatarsal.

Peroneus Longus

This muscle (see Figure 8.22) plantar flexes, everts, and abducts the tarsal joints, and plantar flexes the ankle. It also is most active during the propulsive phase of walking. It is situated superficially on the lateral aspect of the leg with its distal tendon passing behind the lateral malleolus and proceeding forward and downward to the margin of the foot, where it passes behind the tuberosity of the fifth metatarsal. At this point it turns under the foot, passes through the peroneal groove of the cuboid, and slants forward across the plantar surface of the foot to its attachment at the base of the first metatarsal and first cuneiform, not far from the attachment of the tibialis anterior. The muscle belly may be palpated on the lateral surface of the lower half of the leg and just above and behind the lateral malleolus.

Peroneus Brevis

This muscle (see Figures 8.21a and 8.22) plantar flexes and everts and abducts the tarsal joints and helps plantar flex the ankle. It is a penniform muscle, lying beneath the peroneus longus on the lower half of the lateral aspect of the leg. Its tendon passes behind the lateral malleolus immediately anterior to the tendon of longus and continues forward just above the longus tendon to its attachment on the tuberosity of the fifth metatarsal, below the attachment of the peroneus tertius. It may be palpated on the lateral margin of the foot, just posterior to the base of the fifth metatarsal.

Gastrocnemius (Also Listed with the Knee Muscles)

This is a powerful fast-twitch fiber muscle (Figure 8.23) for plantar flexing the foot at the ankle joint. It is the most superficial muscle on the back of the leg and can be seen as two bulges in the upper part of the calf when it is well developed. Its two heads, together with the soleus, constitute the triceps surae. The lateral and medial portions of the muscle remain distinct from each other as far down as the middle of the back of the leg. Then they fuse to form the broad tendon of Achilles.

The most familiar function of this muscle is to enable one to rise on the toes. It has also been shown to be active in most individuals during normal relaxed standing. The muscle has a large angle of pull, approximately 90 degrees when the foot is in its fundamental position. Its internal structure and its leverage combine to make it an exceedingly powerful muscle. The gastrocnemius is more active with the knee extended than with a flexed knee. It is most active in closed kinetic chain activity in the standing position but shows a moderate level of activity when resisted in seated, prone, and supine positions (Carlsson et al. 2001; Tamaki et al. 1997). It may be palpated in the calf of the leg and on the back of the ankle.

Soleus

Like the gastrocnemius, this muscle (Figure 8.24) plantar flexes the foot at the ankle joint. It lies beneath the gastrocnemius, except along the lateral aspect of the lower half of the calf where a portion of it lies lateral to the upper part of the Achilles tendon. Its fibers are inserted into the Achilles tendon in a bipenniform manner. It is predominantly comprised of slow-twitch fibers. In an EMG study of the leg muscles, when the subjects balanced on one foot, the soleus was consistently more active than the gastrocnemius. In another study the soleus was most active in minimal contractions and when the foot was in a dorsiflexed position. This seems to imply that it was especially active in the reduction of dorsiflexion. Campbell and coworkers, using fine wire electrodes, have shown that the medial part of the soleus is a strong dynamic and static plantar flexor, whereas the lateral part is primarily a stabilizer (Basmajian and DeLuca 1985). The muscle may be palpated slightly lateral to and below the lateral bulge of the gastrocnemius.

Tibialis Posterior

This muscle (Figure 8.25) plantar flexes the tarsal joints and helps plantar flex the ankle. It participates in supination (inversion and adduction) when the foot is plantar flexed. It is the deepest muscle on the back of the leg. The main part of the muscle covers the intermuscular septum between the tibia and the fibula. In the lower front of the leg its tendon slants across the medial side of the ankle, passes behind the medial malleolus and above the sustentaculum tali, and then turns under the foot around the medial margin of the navicular bone to insert into its underside. The muscle is penniform in structure. Because of its direction of pull and its numerous attachments on the plantar surface of the tarsal bones, an important function of this muscle appears to be maintenance of the longitudinal arch in a reserve capacity such as is needed in a weak foot.

Flexor Digitorum Longus

This muscle (Figure 8.26) flexes the four lesser toes, plantar flexes and helps invert and adduct the tarsal joints, and helps plantar flex the ankle. It is situated on the medial side of the back of the leg behind the tibia. Penniform in structure, its distal tendon passes behind the medial malleolus between the tendons of the tibialis posterior and flexor hallucis longus. Beneath the tarsal bones it divides into four tendons that go to the distal phalanx of each of the four lesser toes.

Flexor Hallucis Longus

This muscle (Figure 8.26) flexes the great toe, plantar flexes and helps invert and adduct the tarsal joints, and helps plantar flex the ankle. It is situated on the lateral side of the back of the leg, behind the fibula and the lateral portion of the tibia. The fibers unite with the distal tendon in a penniform manner. The tendon crosses behind the ankle to the medial side, passes behind and beneath the sustentaculum tali, and runs forward under the medial margin of the foot to the distal phalanx of the great toe. It is the most posterior of the three tendons that pass behind the medial malleolus. One of its important functions is to provide the push-off in walking, running, and jumping. It may be palpated on the medial border of the calcaneal tendon close to the calcaneus.

Intrinsic Muscles of the Foot

These muscles (Figures 8.27, 8.28, and 8.29) will be treated as a group rather than individually. There are eleven of these small muscles or muscle groups. All but one, the extensor digitorum brevis, are on the plantar surface and are usually described as being arranged in four layers. The dorsal interossei muscles, although included in the deepest layer, are situated between the metatarsal bones rather than on either surface (see Figure 8.21b). The extensor digitorum brevis, which includes the hallucis although the latter is sometimes described as a separate muscle, is situated on the dorsal surface of the foot (see Figure 8.21a). With the exception of the lumbricales and the quadratus plantae, which help flex the lesser toes, the names of these muscles indicate their functions. As one might expect, these intrinsic muscles are much more highly developed in primitive people than in people who habitually wear shoes.

Various research investigations have shown that the intrinsic muscles act as a functional unit, have a significant role in stabilization of the foot during propulsion, and tend to show more activity in feet that are habitually pronated. They do not show activity during relaxed standing in either normal or pronated feet and are not active in the normal static support of the longitudinal arches. They do, however, show definite activity in voluntary attempts to increase the height of the arches. They are also definitely active in the movement of rising on the toes.

Plantar Fascia

On the plantar surface of the foot the muscles are covered by fascia (Figure 8.30), divided into medial, central, and lateral portions. The central portion, known as the plantar aponeurosis, is particularly strong and fibrous. It extends under the whole length of the foot, connecting the tuberosity of the calcaneus with the bases of the proximal phalanges of the five toes. This is an exceedingly strong band that serves as an effective binding rod for the longitudinal arch.

The Ankle

Dorsiflexion

Performed by the tibialis anterior, peroneus tertius, extensor digitorum longus, and extensor hallucis longus.

Plantar Flexion

Performed by the gastrocnemius, soleus, and peroneus longus, with possible help from the tibialis posterior, peroneus brevis, flexor digitorum longus, and flexor hallucis longus.

The Tarsal Joints

Dorsiflexion

The same as for dorsiflexion of the ankle.

Plantar Flexion

Performed by the tibialis posterior, flexor digitorum longus, flexor hallucis longus, and peroneus longus and brevis.

Supination (Inversion and Adduction) (Figure 8.31b)

Performed by the tibialis anterior (when the foot is dorsiflexed) and tibialis posterior (when the foot is plantar flexed), with possible help from the flexor digitorum longus and flexor hallucis longus (Basmajian and DeLuca 1985).

Pronation (Eversion and Abduction) (Figure 8.31a)

Performed by the peroneus longus, brevis, and tertius, with possible help from the extensor digitorum longus.

The Toes (Exclusive of the Intrinsic Muscles)

Flexion

Performed by the flexor digitorum longus and flexor hallucis longus.

Extension

Performed by the extensor digitorum longus and extensor hallucis longus.

Maintenance of the Arches

The arches of the foot are maintained by a combination of bony structure, aponeuroses, ligaments, and tendons. The irregular tarsal bones fit together to form the basic structure of the longitudinal arch. The plantar fascia and the tendons of the deep plantar flexors act as a cable holding the arch shape. The spring ligament, the deltoid ligament, and the interosseus ligaments provide stability within the tarsal region and between the tarsal bones and the talus.

In a strong foot, muscle activity is involved for balance, adjusting the foot when encountering uneven surfaces, during locomotion, and when incurring other stresses such as standing on tiptoes. In a weak foot, such as with flat feet, muscles play a greater role. However, it has been demonstrated consistently that bones and ligaments are the primary structures for maintaining the arches.

The Leg

Shin Contusions

These injuries are very common because of the exposed position of the tibia and its lack of protection. A direct blow may cause an injury that varies in severity all the way from a simple bruise to a severe traumatic tibial periostitis, a condition in which the periosteum may be seriously damaged. Unlike the femur, the tibia has no anterior muscles to cushion it against sharp blows. It is important, therefore, to make every effort to protect the bone by the use of shin guards or other forms of padding in activities where there is a high risk of shin bruising.

Tibial Stress Injuries

Conditions associated with overuse or repeated stress to the tibia, the fascia, and the anterior compartment of the shank have often been lumped under the catch-all term “shin splints.” In reality, pain or discomfort in the medial anterior region of the shank may be the result of any number of conditions. Micro tears of muscle or fascia, increased pressure in the various soft tissue compartments, stress fractures of the tibia, and inflammation of the fascia (fasciitis) can all lead to symptoms of pain and tenderness. The onset is gradual and the condition may be due to repeated tiny tears where the tibialis posterior or anterior attaches to the tibia or to tears or sprains in the interosseous membrane. Softer surfaces and supporting the arches may be helpful in relieving the symptoms, but rest is often necessary for recovery.

Leg Fracture

Fractures of the tibia, the fibula, or both are most common among young people. The severity of the fracture is usually determined by the degree to which bone segments are displaced. A nondisplaced fracture of the fibula is a much less severe injury than a displaced fracture of both the tibia and the fibula. In any case, fractures should be treated as serious injuries, as there may be a concomitant injury to the epiphysis and to other soft tissue structures that will lead to permanent instability or dysfunction.

The Knee

Vulnerability of the Knee Joint

There can be no question as to the vulnerability of the knee. It is probably the most susceptible to injury of any of the joints in the body. Two factors appear to be responsible for this: its complicated structure and its position midway between the hip and the sole of the foot. Superficially, it looks like a hinge joint, but its action combines the movements of a hinge with the gliding of an irregular joint. Furthermore, when it is flexed it is capable of a slight degree of medial and lateral rotation. Several writers have called attention to the strains and stresses to which the knee is subject and have emphasized the need to be aware of these forces for knee function. Additionally, misalignments that cause the unequal or off-center transmission of forces through the knee joint are predisposing factors contributing to knee injuries. Common examples of these conditions are knock-knees (genu valgum) and bowlegs (genu varum). In knock-knees (genu valgum) the knees are closer to the midline of the body than is normal. In the standing position the knees are closer together than the feet, so that when the feet are placed side by side, the knees are either pressed together or are slightly overlapping with one behind the other. Mechanically, the condition means that the weight-bearing line of the lower extremity passes lateral to the center of the knee joint. This puts the medial ligament (tibial collateral) under increased tension and subjects the lateral meniscus to increased pressure and friction. Such a joint is unstable. Not only is it more prone to injury than a well-aligned joint, but in all weight-bearing positions postural strains are constantly present. The condition of bowlegs (genu varum) is just the reverse of knock-knees, with the additional complication of the long bones themselves being curved laterally.

When the knee is in flexion, it is in an open position, with stability maintained by muscle, tendon, and ligament. In a weight-bearing situation, such as a squat, the body weight is borne primarily by the soft tissue structures, with little bony support.

In downward movement, the hip and knee joints are flexing and the ankle joints are dorsiflexing. The joint movements are caused by the force of gravity; they are controlled by the muscles that normally cause the opposite movements but that, for this purpose, are engaged in eccentric contraction. In the return movement—that is, the return to the erect standing position—the same muscles are working but this time in concentric contraction.

The demands placed on the muscles and ligaments of the knee joint during deep squats are severe. These factors should be considered when contemplating the assignment of exercises involving repeated full squats or long-held squat positions.

Contusion

This condition occurs frequently among athletes and can be caused either by a fall or by a blow against the front or side of the knee. The problem presented by a contusion of the knee is that it often masks a more serious injury, such as ligament damage. Therefore, if there is uncertainty, this injury should be treated as the more serious injury to prevent further deterioration.

Collateral Ligament Sprain

This is doubtless one of the most, if not the most, frequently reported knee injury, at least in the world of sports (Arnheim and Prentice 1998). To understand the reason for this, a thorough knowledge of the structure of the joint is essential (see Structure and Figure 8.32). Although classified as a hinge joint, it is by no means a typical one like the interphalangeal finger joints, for instance. In flexion and in the return from flexion, a certain amount of gliding occurs. When the knee is flexed, it is capable of a slight amount of voluntary rotation. When it receives a blow from the side or when it is subjected to severe wrenching in the weight-bearing position, it can easily be forced beyond its normal range of rotary motion. Furthermore, although abduction and adduction are not normal knee motions—that is, one cannot voluntarily perform them—the leg can be passively abducted or adducted by an outside force. A slight degree of this probably does no harm, but a severe lateral blow or violent wrenching is likely to tear the ligament on the opposite side.

Because the knee is protected medially, the majority of knee sprains are caused by a blow from the lateral side toward the medial side or by a severe medialward twist (Arnheim and Prentice 1998). This means that the leg has been violently adducted and medially rotated at the knee joint. The stress is primarily on the ligaments on the inner side of the knee. If the force is great enough to be transmitted to the deep layer of the medial collateral ligament, it is likely to affect the medial meniscus, which is attached to the ligament. Injuries to the lateral side are much less common. Cruciate ligament sprain and rupture are often encountered when forces cause the tibia to move forward or backward.

Strengthening of the muscles that cross the knee joint is an important part of the rehabilitation of injured knee joints. The muscles and their tendons help stabilize the joint and provide support that may be compromised because of the damaged ligaments. Moreover, it is important to maintain the strength of these muscles for their stabilizing role in sustaining the integrity of the joint and preventing injuries to it.

Chondromalacia

Chondromalacia of the patella most often occurs among young adults and affects the cartilage on the articulating surface of the patella. The etiology of this degenerating disease is unknown, but it is conjectured that an incongruence between the patella and the femur may contribute to it. Common symptoms include pain upon movement, swelling, and a grating sensation. Treatment includes doing isometric exercises, wearing a band (brace) for support, and limiting certain activities.

Osgood-Schlatter Disease

Osgood-Schlatter disease, affecting adolescents, is caused by repeated usage of the knee extensors, resulting in a tearing or avulsion at the epiphysis of the tibial tuberosity, the point for attachment of the patellar tendon. Symptoms include swelling, hemorrhage, and pain when running, jumping, or kneeling. Treatment includes ice therapy, rest, and subsequent isometric strengthening exercises.

The Ankle

Of all the injuries to which the lower extremity is prone, those affecting the ankle joint have the highest incidence. One reason for this is thought to be the arrangement of the muscles. The long tendons cross the ankle in a way that makes for a lack of bulk and for good leverage but contributes little to stabilization (Arnheim and Prentice 1998). Consequently, this joint is unusually susceptible to strains, sprains, dislocations, and fractures.

Strains

A strain is a muscle injury. This includes the muscle tendon and the connective tissue by means of which the muscle is attached to the bone. Landing from jumping exposes the tendons of the ankle and foot muscles to the danger of strain. The impact of landing may force the ankle joints beyond their normal range of motion. This gives the Achilles tendon a sudden wrench that may cause tearing, either at the point of the tendon’s attachment to the bone or at the junction between the tendon and the muscle belly. This is potentially a very debilitating injury requiring expert treatment.

The distal tendons of both the anterior and posterior tibial muscles are also subject to strain. The aftereffects of each of these can be quite troublesome because they are both inverters (supinators) of the foot, in addition to which the posterior tibial helps support the longitudinal arch in weak feet or under exceptional stress.

Sprains

A sprained ankle is all too familiar. It results from a sudden wrench or twist and is usually associated with forced inversion of the foot with the lateral ligaments being stretched or torn and sometimes ruptured or pulled off of the bone. The affected ligaments are any of those on the lateral aspect of the ankle—the calcaneofibular, anterior talofibular, and posterior talofibular. The interosseous talocalcaneal ligament, although not strictly an ankle ligament, may also be affected.

Fractures

Ankle fractures are usually caused by a sudden wrenching or twisting, the same factors that cause sprains but, whereas sprains are the result of excessive inversion of the foot, fractures result from excessive eversion. The majority of ankle fractures occur to the malleoli, especially the lateral malleolus. In the more serious fractures, some dislocation as the result of a separation between the tibia and fibula is also likely, with a consequent widening of the socket or mortise. Prompt and adequate treatment to restore the joint integrity is all important if permanent damage is to be avoided.

The Foot

Plantar Fasciitis

Plantar fasciitis is a broad term used to describe pain and tenderness along the sole of the foot. This condition may be due to inflammation of the plantar fascia, micro tears of the fascia, or a complete rupture. Plantar fasciitis is generally an overuse injury, but lack of flexibility in the muscles of the lower extremity may also be a contributing factor. Tension in the muscles of the lower leg will produce tension in the plantar fascia, and over the long term, the plantar fascia will be damaged. Stretching has been shown to be helpful in both prevention and treatment of plantar fasciitis (Whiting and Zernicke 1998).

Knee Joint: Joint Structure and Function

• 1. Record the essential information regarding the structure, ligaments, and cartilages of the knee joint. Study the movements both on the skeleton and on the living body and explain how the joint structure affects movements.

Muscular Action

Identify as many muscles as possible in the following experiments.

• 2. Flexion at Knee
  • Subject: Lie face down and flex leg at knee by raising foot.
  • Assistant: Steady subject’s thigh and resist movement by pushing down on ankle.
  • Observer: Palpate biceps femoris, semitendinosus, gracilis, sartorius, and gastrocnemius.
• 3. Extension at Knee
  • a. Subject: Rise from a squat position.
    • Observer: Palpate quadriceps femoris.
  • b. Subject: Sit on table with legs hanging over edge. Extend leg.
    • Assistant: Steady subject’s thigh and resist movement by holding ankle down.
    • Observer: Palpate quadriceps femoris.
• 4. Outward Rotation of Leg with Knee in Flexed Position
  • Subject: Sit on table with legs hanging over edge. Rotate foot laterally as far as possible without moving thigh.
  • Assistant: Steady subject’s thigh and give slight resistance by holding foot.
  • Observer: Palpate biceps femoris.
• 5. Inward Rotation of Leg with Knee in Flexed Position
  • Subject: Sit on table with legs hanging over edge. Rotate foot medially as far as possible without moving thigh.
  • Assistant: Steady subject’s thigh and give slight resistance by holding foot.
  • Observer: Palpate semitendinosus, gracilis, and sartorius.

Ankle and Foot: Joint Structure and Function

• 6. Record the essential information regarding the structure, ligaments, and cartilages of the ankle, subtalar, and midtarsal joints. Study the movements of these joints both on the skeleton and on the living body and explain how the joint structures affect the movements.
• 7. Using a goniometer, compare the total range of plantar and dorsiflexion of the ankle in a group of five or more subjects (a) with extension at the knee and (b) with flexion at the knee.
• 8. Make a similar comparison between two groups, one consisting of three to five varsity-level swimmers and the other of the same number of recreational swimmers, or make a similar comparison between ballet and nonballet dancers.

Ankle and Foot: Muscular Action

Identify as many muscles as possible in the following experiments.

• 9. Plantar Flexion
  • Subject: Perform each of the following actions: a. Stand and rise on the toes. b. Hold one foot off the floor and extend it vigorously.
  • Observer: Compare the muscular action of the leg in a and b.
• 10. Dorsiflexion
  • Subject: Sit on a table with the legs straight and with the feet over the edge. Dorsiflex one foot as far as possible.
  • Assistant: Resist the movement by holding the foot.
  • Observer: Identify the tibialis anterior, peroneus tertius, extensor digitorum longus, and extensor hallucis longus.
• 11. Pronation (Eversion and Abduction)
  • Subject: In same starting position as in Experience 10, pronate one foot without extending it.
  • Assistant: Steady the leg at the ankle and resist the movement by holding the foot.
  • Observer: Identify the muscles that contract.
• 12. Supination (Inversion and Adduction)
  • Subject: In same position as in Experience 10, supinate one foot as far as possible.
  • Assistant: Steady the leg at the ankle and resist the movement by holding the foot.
  • Observer: Identify the muscles that contract.

Kinesiological Analysis

• 13. Choose a simple motor skill from Appendix G. Do a complete anatomical analysis of the lower extremity following the analysis outline in Table 1.2.