REIDER PART 2
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ChaPTi-r 7_Lower Leg, Foot, and Ankle 283

tear. In severe injuries, thc examiner is able to detect a smali divot at this location. This injury is sometimes called tettnis leg. Injuries may also occur at thc latcral musculotendinous junction or further distally in the aponeurotic section of the gastrocsoleus. Such injuries should not be associated with an abnormal response to the Thompson test (see Manipulation section).

Injuries of the Achilles tendon itself usually occur a few centimeters proximal to the insertion of the tendon on the calcaneus. In the presence of an acute rupture, localized swelling usually obscures the outlines of the tendon, but careful palpation reveals a gap in the firm tendon about 2 cm or 3 cm proximal to the calcaneus. The response to the Thompson test is abnormal in the presence of a complete Achilles rupture.

In chronic Achilles* tendiniti$_y the tendon is most commonly tender at the same site, approximately 2 cm to 3 cm proximal to the calcaneus (see Fig. 7-15). In milder cases, the tendon appears normal, but in morę severe cases, a palpable and even visible thickening is present. Heel. Tenderness at the insertion of the Achilles tendon into the posterior tuberosity of thc calcaneus is most commonly caused by retrocalcaneal bursitis, inflammation of the retrocalcaneal bursa. Tenderness at this location may less commonly be caused by calcific tendinitis of thc Achilles insertion itself. Although thesc two entities may be difficult to dislinguish clinically, tenderness on both sides of the Achilles insertion as well as over the insertion itself supports a diagnosis of retrocalcaneal bursitis. Retrocalcaneal bursitis may be associated with Haglund's deformity> an inerease in the normal prominence of the posterior calcaneal tuberosity. Haglunds deformity itself may cncouragc thc development of subcutaneous bursitis owing to the extrin-sic pressure of the adjacent shoe. Such bursitis involves inflammation of the subcutaneous bursa between the calcaneal tuberosity and the overlying skin (see Fig. 7-11). Sural Nerve. Sural nerve entrapment may occur owing to posttraumatic scarring, most commonly following surgery or ankle sprains. In the distal leg, the nerve runs along the lateral border of the Achilles tendon. About 2 cm above the ankle it branches. One branch supplies sensation to the lateral heel, and the other frequcntly anastomoses with the latcral branch of thc superficial peroneal nerve. The nerve then runs inferior to the peroneal tendon sheath in a subcutaneous position (sec Figs. 7-11 and 7-15). As it rcachcs the tuberosity of the fifth metatarsal, the nerve ramifies to provide sensation to the lateral aspect of the fifth toe and the fourth web spacc. Sural nerve entrapment may occur anywhere along this course. Patients may givc thc history of a previous twisting injury with the subseąuent develop-ment of shooting pain and paresthesias. If such a history is elicited, the examiner should check for tenderness and a Tinel sign along the course of the nerve just described. Characteristically, the nerve is tender, and the Tinel sign is elicited at the site of nerve entrapment.

Medial Aspect

Lower Leg and Ankle. The medial malleolus is nor-mally the most prominent structure of the medial ankle and foot. As on the lateral side, traumatic fractures involving thc medial malleolus are usually associated with considerablc swelling, ecchymosis, tenderness, and sometimes crepitus. Stress fractures of thc medial malleolus are unusual and thus easy to overlook. Tenderness in such stress fractures usually occurs about 2 cm to 3 cm proxi-mal to the tip of the malleolus (see Fig. 7-20). Continuing to palpate further proximaiły, the examiners hand may explore the entire posteromedial subcutaneous border of the tibia. The most common site for stress fractures of the tibia is on the posteromedial cortex at the junction of the middle and distal thirds of the bonę (see Fig. 7-23). Localized bony tenderness at this site usually is highly suggestive of a stress fracture. If thc stress fracture has been present for several weeks or morę, thc examiner may be able to detect a smali, firm, tender lump on the posteromedial tibia that represents the periosteal new bonę formation in response to the stress fracture. Morę diffuse tenderness along thc posteromedial tibia is morę likely to represent the overuse syndrome known as shin splints or periostitis.

The deltoid ligament connects the medial malleolus with the adjacent talus and medial calcaneus. The incli-vidual fascicles of this ligament cannot be distinguished by palpation; however, tenderness, swelling, and ecchymosis over the deltoid ligament suggest a sprain involving this structure. Such an injury may be difficult to differen-tiate from damage to the posterior tibial tendon.

Passive eversion of the hindfoot also exposes the medial head of the talus, located just distal and anterior to the medial malleolus. In a patient with severe flatfoot, the medial talar head is already prominent. In the most severe cases of flatfoot, a diffuse callus caused by friction or weightbearing can be found overlying the medial aspect of the talar head.

About 2 cm distal and anterior to thc tip of the medial malleolus lies the navicular tuberosity. Eversion of the foot inereases the prominence of the tuberosity. Tenderness of the tuberosity, especially when it is morę prominent than usual, suggests a symptomatic accessory navicular. This developmental variant may become painful through chronic overuse or acute trauma.

The posterior tibial tendon courses from behind the medial malleolus to insert on the navicular tuberosity. The tendon can be rendered morę easily palpable by asking the patient to invert the foot against resistance (see Fig. 7-22). Tenderness posterior to the medial malleolus or further distal along the course of the tendon suggests thc possibil-ity of posterior tibial tendinitis. The association of localized swelling suggests morę severe tendinitis or even rupture. Chronic tendinitis or rupture of thc posterior tibial tendon can result in secondary collapse of the arch of the foot.