OPLITEAL FOSSA AND LEG Popliteal Abscess and Tumor Because the deep popliteal ascia is strong and lim- its expansion, pain rom an abscess or tumor in the popliteal ossa is usually severe. Popliteal abscesses tend to spread superiorly and ineriorly because o the tough- ness o the popliteal ascia. Popliteal Pulse Because the popliteal artery is deep, it may be di- cult to eel the popliteal pulse. Palpation o this pulse is commonly perormed with the person in Popliteal Fossa and Leg 763 to the our lateral digits. The tendon o the FT may be pal- pable lateral to the tendons o the EDL, especially when the oot is dorsifexed and everted. The shat o the bula is subcutaneous only in its distal part, proximal to the lateral malleolus; this is the common site o ractures. The medial and lateral malleoli are subcu- taneous and prominent. Palpate them, noting that the tip o the lateral malleolus extends arther distally and posteriorly than the medial malleolus. The bularis longus (FL) is subcutaneous throughout its course (Fig. 7.67C). The tendons o this muscle and the bularis brevis (FB) are palpable when the oot is everted as they pass around the posterior aspect o the lateral malleolus. These tendons may be ollowed anteriorly along the lateral side o the oot. The tendon o the FL runs as ar anteriorly as the cuboid and then disappears by turning into the sole o the oot. The tendon o the FB may be traced to its attachment to the base o the 5th metatarsal. The calcaneal tendon can be easily ollowed to its attach- ment to the calcaneal tuberosity, the posterior part o the calcaneus. The ankle joint is airly supercial in the depres- sion on each side o the calcaneal tendon. The heads o the gastrocnemius are easily recognizable in the superior part o the cal o the leg (Fig. 7.67B, C). The soleus can be palpated deep to and at the sides o the superior part o the calcaneal tendon. The triceps surae (soleus and gastrocnemius) is easy to palpate when the individual is standing on the toes. The soleus can be distinguished rom the gastrocnemius during squatting (fexing the knees while standing on toes) because fexion o the knee to approximately 90° makes the gastrocne- mius faccid; plantarfexion in this position is maintained by the soleus. The deep muscles o the posterior compartment are not easily palpated, but their tendons can be observed just posterior to the medial malleolus, especially when the oot is inverted and the toes are fexed. the prone position with the knee fexed to relax the popliteal ascia and hamstrings. The pulsations are best elt in the ine- rior part o the ossa where the popliteal artery is related to the tibia. Weakening or loss o the popliteal pulse is a sign o a emoral artery obstruction. Popliteal Aneurysm and Hemorrhage A popliteal aneurysm (abnormal dilation o all or part o the popliteal artery) usually causes edema and pain in the popliteal ossa. A popli- teal aneurysm may be distinguished rom other masses by palpable pulsations (thrills) and abnormal arterial sounds (bruits) detectable with a stethoscope. Because the artery 7 764 764 Chapter 7 Lower Limb Chapter 7 Lower Limb lies deep to the tibial nerve, an aneurysm may stretch the nerve or compress its blood supply (vasa vasorum). Pain rom such nerve compression is usually reerred, in this case to the skin overlying the medial aspect o the cal, ankle, or oot. Because the popliteal artery is closely applied to the popliteal surace o the emur and the joint capsule (see Fig. 7.60), ractures o the distal emur or dislocations o the knee may rupture the artery, resulting in hemorrhage. Furthermore, because o their proximity and connement within the popliteal ossa, an injury o the artery and vein may result in an arteriovenous stula (communication between an artery and a vein). Failure to recognize these occurrences and to act promptly may result in the loss o the leg and oot. I the emoral artery must be ligated, blood can bypass the occlusion through the genicular anastomosis and reach the popliteal artery distal to the ligation (see Fig. 7.53). Injury to Tibial Nerve Injury to the tibial nerve is uncommon because o its deep and protected position in the popliteal ossa; however, the nerve may be injured by deep lacerations in the ossa. Posterior dislocation o the knee joint may also damage the tibial nerve. Severance o the tibial nerve produces paralysis o the fexor muscles in the leg and the intrinsic muscles in the sole o the oot. People with a tibial nerve injury are unable to plantarfex their ankle or fex their toes. Loss o sensation also occurs on the sole o the oot. Containment and Spread o Compartmental Inections in Leg The ascial compartments o the lower limbs are generally closed spaces, ending proximally and dis- tally at the joints. Because the septa and deep ascia o the leg orming the boundaries o the leg compartments are strong, the increased volume consequent to inection with suppuration (ormation o pus) increases intracom- partmental pressure. Infammations within the anterior and posterior compartments o the leg spread chiefy in a dis- tal direction; however, a purulent (pus-orming) inection in the lateral compartment o the leg can ascend proximally into the popliteal ossa, presumably along the course o the bular nerve. Fasciotomy (incision o ascia) may be neces- sary to relieve pressure and debride (scrape away) pockets o inection. Tibialis Anterior Strain (Shin Splints) Shin splints—edema and pain in the area o the distal two thirds o the tibia—result rom repeti- tive microtrauma o the tibialis anterior (TA; Fig. 7.57A), which causes small tears in the periosteum cov- ering the shat o the tibia and/or o feshy attachments to the overlying deep ascia o the leg. Shin splints are a mild orm o the anterior compartment syndrome. Shin splints com- monly occur during traumatic injury or athletic overexertion o muscles in the anterior compartment, especially TA, by untrained persons. Oten, persons who lead sedentary lives develop shin splints when they participate in long-distance walks. Shin splints also occur in trained runners who do not warm up and cool down suciently. Muscles in the anterior compartment swell rom sudden overuse, and the edema and muscle–tendon infammation reduce the blood fow to the muscles. The swollen muscles are painul and tender to pressure. Fibularis Muscles and Evolution o Human Foot Whereas the eet o anthropoids (higher pri- mates) are inverted so that they walk on the outer border o the oot, the eet o humans are rela- tively everted (pronated) so that the soles lie more ully on the ground. This pronation is the result, at least in part, o the medial migration o the distal attachment o the bu- laris longus across the sole o the oot (Fig. 7.62K) and the development o a bularis tertius that is attached to the base o the 5th metatarsal. These eatures are unique to the human oot. Injury to Common Fibular Nerve and Footdrop Because o its supercial position, the common bular nerve is the nerve most oten injured in the lower limb, mainly because it winds subcu- taneously around the bular neck, leaving it vulnerable to direct trauma (see Fig. 7.58A). This nerve may also be severed during racture o the bular neck or severely stretched when the knee joint is injured or dislocated. Severance o the common bular nerve results in faccid paralysis o all muscles in the anterior and lateral compart- ments o the leg (dorsifexors o ankle and evertors o oot). The loss o dorsifexion o the ankle causes ootdrop, which is urther exacerbated by unopposed inversion o the oot. This has the eect o making the limb “too long”: the toes do not clear the ground during the swing phase o walking (Fig. B7.21A, E). There are several other conditions that may result in a lower limb that is “too long” unctionally, or example, pelvic tilt (see Fig. B7.19C) and spastic paralysis or contraction o the soleus. There are at least three means o compensating or this problem: 1. A waddling gait, in which the individual leans to the side opposite the long limb, “hiking” the hip (Fig. B7.21B). 2. A swing-out gait, in which the long limb is swung out laterally (abducted) to allow the toes to clear the ground (Fig. B7.21C). Popliteal Fossa and Leg 765 Popliteal Fossa and Leg 765 (A) (B) (C) (D) (E) FIGURE B7.21. 3. A high-stepping steppage gait, in which extra fexion is employed at the hip and knee to raise the oot as high as necessary to keep the toes rom hitting the ground (Fig. B7.21D, E). Because the dropped oot makes it dicult to make the heel strike the ground rst as in a normal gait, a steppage gait is commonly employed in the case o faccid paralysis. Sometimes, an extra “kick” is added as the ree limb swings orward in an attempt to fip the oreoot upward just beore setting the oot down. The braking action normally produced by eccentric con- traction o the dorsifexors is also lost in faccid paralysis oot- drop. Thereore, the oot is not lowered to the ground in a controlled manner ater heel strike; instead, the oot slaps the ground suddenly, producing a distinctive “clop” and greatly increasing the shock both received by the oreoot and transmitted up the tibia to the knee. Individuals with a common bular nerve injury may also experience a variable loss o sensation on the anterolateral aspect o the leg and the dorsum o the oot. Deep Fibular Nerve Entrapment Excessive use o muscles supplied by the deep bu- lar nerve (e.g., during skiing, running, and danc- ing) may result in muscle injury and edema in the anterior compartment. This entrapment may cause com- pression o the deep bular nerve and pain in the anterior compartment. Compression o the deep bular nerve by tight-tting ski boots, or example, may occur where the nerve passes deep to the inerior extensor retinaculum and the extensor hallucis brevis (see Fig. 7.55A). Pain occurs in the dorsum o the oot and usually radiates to the web space between the 1st and 2nd toes. Because ski boots are a common cause o this type o nerve entrapment, this condition has been called the “ski boot syndrome”; however, the syndrome also occurs in soc- cer players and runners and can also result rom tight shoes. Superfcial Fibular Nerve Entrapment Chronic ankle sprains may produce recurrent stretching o the supercial bular nerve, which may cause pain along the lateral side o the leg and the dorsum o the ankle and oot. Numbness and paresthesia (tickling or tingling) may be present and increase with activity. Fabella in Gastrocnemius Close to its proximal attachment, the lateral head o the gastrocnemius may contain a sesamoid bone, the abella (L., bean), which articulates with the lateral emoral condyle. The abella is visible in lateral radio- graphs o the knee in 3–5% o people (Fig. B7.22). Calcaneal Tendinitis Infammation o the calcaneal tendon constitutes 9–18% o running injuries. Microscopic tears o col- lagen bers in the tendon, particularly just superior 7 7 Femur Patella Fabella Fibula Tibia Lateral view FIGURE B7.22. 766 766 Chapter 7 Lower Limb Chapter 7 Lower Limb to its attachment to the calcaneus, result in tendinitis, which causes pain during walking, especially when wearing rigid- soled shoes. Calcaneal tendinitis oten occurs during repeti- tive activities, especially in individuals who take up running ater prolonged inactivity, or suddenly increase the intensity o their training, but it may also result rom poor ootwear or training suraces. Ruptured Calcaneal Tendon Rupture o the calcaneal tendon is oten sustained by poorly conditioned people with a history o cal- caneal tendinitis. The injury is typically experienced as an audible snap during a orceul push o (plantarfexion with the knee extended) ollowed immediately by sudden cal pain and sudden dorsifexion o the plantarfexed

Ruptured Calcaneal Tendon Rupture o the calcaneal tendon is oten sustained by poorly conditioned people with a history o cal- caneal tendinitis. The injury is typically experienced as an audible snap during a orceul push o (plantarfexion with the knee extended) ollowed immediately by sudden cal pain and sudden dorsifexion o the plantarfexed oot. In a completely ruptured tendon, a gap is palpable, usually 1–5 cm proximal to the calcaneal attachment. The muscles aected are the gastrocnemius, soleus, and plantaris. Calcaneal tendon rupture is probably the most severe acute muscular problem o the leg. Individuals with this injury cannot plantarfex against resistance (cannot raise the heel rom the ground or balance on the aected side), and passive dorsifexion (usually limited to 20° rom neutral) is excessive. Ambulation (walking) is possible only when the limb is laterally (externally) rotated, rolling over the transversely placed oot during the stance phase without push o. Bruising appears in the malleolar region, and a lump usu- ally appears in the cal owing to shortening o the triceps surae. In older or nonathletic people, nonsurgical repairs are oten adequate, but surgical intervention is usually advised or those with active liestyles, such as tennis players. Calcaneal Tendon Reex The ankle jerk refex, or triceps surae refex, is acalca- neal tendon refex. It is a myotatic refex elicited while the person’s legs are dangling over the side o the examining table. The calcaneal tendon is struck briskly with a refex hammer just proximal to the calcaneus (Fig. B7.23). The normal result is plantarfexion o the ankle joint. The calcaneal tendon refex tests the S1 and S2 nerve roots. I the S1 nerve root is injured or compressed, the ankle refex is virtually absent. Calcaneal tendon FIGURE B7.23. Absence o Plantarexion I the muscles o the cal are paralyzed, the cal- caneal tendon is ruptured, or normal push o is painul, a much less eective and ecient push o (rom the midoot) can still be accomplished by the actions o the gluteus maximus and hamstrings in extending the thigh at the hip joint and the quadriceps in extending the knee. Because push o rom the oreoot is not possible (in act, the ankle will be passively dorsifexed as the body’s weight moves anterior to the oot), those attempting to walk in the absence o plantarfexion oten rotate the oot as ar later- ally (externally) as possible during the stance phase to dis- able passive dorsifexion and allow a more eective push o through hip and knee extension exerted at the midoot. Gastrocnemius Strain Gastrocnemius strain (tennis leg) is a painul acute injury resulting rom partial tearing o the medial belly o the gastrocnemius at or near its musculo- tendinous junction, oten seen in individuals older than 40 years o age. It is caused by overstretching the muscle by concomitant ull extension o the knee and dorsifexion o the ankle joint. Usually, an abrupt onset o stabbing pain is ollowed by edema and spasm o the gastrocnemius. Calcaneal Bursitis Calcaneal bursitis (retro-Achilles bursitis) results rom infammation o the deep bursa o the calca- neal tendon, located between the calcaneal tendon and the superior part o the posterior surace o the calcaneus (Fig. B7.24). Calcaneal bursitis causes pain posterior to the heel and occurs commonly during long-distance running, basketball, and tennis. It is caused by excessive riction on the bursa as the tendon continuously slides over it. Venous Return From Leg A venous plexus deep to the triceps surae is involved in the return o blood rom the leg. When a person is standing, the venous return rom the leg depends largely on the muscular activity o the triceps surae Calcaneal tendon Deep calcaneal bursa FIGURE B7.24. (see “Venous Drainage o Lower Limb” in this chapter). Contraction o the cal muscles pumps blood superiorly in the deep veins. The musculovenous pump is improved by the deep ascia that invests the muscles like an elastic stocking. Accessory Soleus An accessory soleus is present in approximately 3% o people (Fig. B7.25). The accessory muscle usu- ally appears as a distal belly medial to the calcaneal tendon. Clinically, an accessory soleus may be associated with pain and edema (swelling) during prolonged exercise. Gastrocnemius Soleus Accessory soleus Posterior view FIGURE B7.25. The Bottom Line POPLITEAL FOSSA AND LEG Popliteal ossa: The popliteal ossa is a at-flled and relatively confned compartment posterior to the knee that is traversed by all neurovascular structures passing between the thigh and the leg. ● The sciatic nerve biurcates at the apex o the ossa, with the common fbular nerve passing laterally along the biceps tendon. ● The tibial nerve, popliteal vein, and popliteal artery bisect the ossa—in that order, rom superfcial (posterior) to deep (anterior). ● Genicular branches o the popliteal artery orm a peri-articular genicular anastomosis around the knee, providing collateral circulation to maintain blood ow in all positions o the knee. Popliteal Fossa and Leg 767 Popliteal Fossa and Leg 767 Posterior Tibial Pulse The posterior tibial pulse can usually be palpated between the posterior surace o the medial malleo- lus and the medial border o the calcaneal tendon (Fig. B7.26). Because the posterior tibial artery passes deep to the fexor retinaculum, it is important when palpating this pulse to have the person invert the oot to relax the retinacu- lum. Failure to do so may lead to the erroneous conclusion that a pulse is absent. Both arteries are examined simultaneously or equal- ity o orce. Palpation o the posterior tibial pulses is essential or examining patients with occlusive periph- eral arterial disease. Although posterior tibial pulses are absent in approximately 15% o normal young people, absence o posterior tibial pulses is a sign o occlusive peripheral arterial disease in people older than 60 years. For example, intermittent claudication, characterized by leg pain and cramps, develops during walking and disap- pears ater rest. These conditions result rom ischemia o the leg muscles caused by narrowing or occlusion o the leg arteries.

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