REIDER PART 210

270_Chapter 7 Lower Leg, Foot> and Ankle

Figurę 7-35. A, Walking on the lateral border of the right foot. B, Externally rotating the lower limb to accommodate an equinus contracture of the ankle.

examination of each joint in a systematic manner with comparison to the opposite extremity is necessary. However, the patienfs complaints and other physical signs often permit the clinician to focus the examination on the area of principal interest. It is usually most effi-cient to integrate the active and passive motion exami-nations by first asking the patient to move a joint actively and then manipulating it passively when indicated. The gross functional tests described under the Muscle Testing section-heel walking, toe walking, and walking on the medial and lateral borders of the feet-provide a useful quick assessment of the functioning capabilities of the ankle and the subtalar joints in particular. For morę detailed information, each joint needs to be isolated individually.

Ankle

Dorsiflexion. The principal motions of the ankle joint are dorsiflexion and plantar flexion. Both of these motions are usually assessed with the patient in the sit-ting position. To examine active dorsiflexion, the patient is asked to puli the foot up toward the leg as far as possible (Fig. 7-36,4). To compare passive dorsiflexion, the examiner grips the hindfoot in neutral, iiwerts the forefoot, and passively dorsiflexes the ankle to the maxi-mal degree possible (Fig. 7-36B). Inversion of the forefoot minimizes the contribution of the forefoot joints to sagittal motion, so that a morę accurate recording of pure ankle motion is achieved.

The magnitude of ankle dorsiflexion is assessed by measuring or estimating the angle between the plantar surface of the foot and a linę perpcndicular to the longi-tudinal axis of the lower leg. Normal ankle dorsiflexion avcrages about 20°.

Causes of Lost Dorsiflexion. Loss of dorsiflexion may be due to contracture of posterior structures, such as the Achilles tendon complex; loss of flexibility in the ankle syndesmosis; or impingement of anterior soft tissue or osteophytes. An ankle that cannot cven dorsiflex to a neutral position is said to be in equinus.

If the Achilles tendon complcx appears to be responsi-ble for limiting dorsiflexion, further testing may allow the examiner to determine whether or not this is caused by an isolated contracture of the gastrocnemius portion of the Achilles complex. To make this determination, the exam-iner assesses the passive dorsiflexion of the ankle in two positions: with the knee fully extended and with the knee flexed 90°. Extending the knee tightens the gastrocnemius portion of the Achilles complex because it originates above the knee. Flexing the knee allows the gastrocnemius to relax. Thus, when an isolated contracture of the gastrocnemius is present, less passive dorsiflcxion is present with the knee fully extended than when it is flexed. If contracture of the soleus is the limiting factor, the position of the knee does not affect the amount of ankle dorsiflexion possible.

Because the dome of the talus is wider anteriorly, the distal fibula and tibia must slightly separate at the tibiofibular syndesmosis to allow fuli dorsiflexion to