The ankle's muscular, capsular, and bony structures must absorb and dissipate normal and abnormal forces. Ankle sprains are frequently cited as the most common sports-related injuries and have a high reinjury rate, secondary to chronic laxity of the ligaments and/or the subsequent loss of the joint's sense of position caused by injury to proprioceptors.1,2 Seemingly minor injuries, such as contusions, can have severe consequences resulting from compression of the neurovascular structures of the ankle, foot, and toes. Trauma or dysfunction of the ankle and leg muscles can lead to biomechanical changes, causing gait deviations that lead to further injury. Different foot types are associated with gait pattern deviations that may redistribute stresses on bones and demands son the muscles of the lower extremity. Examination of the ankle must also include the trunk and lower extremity to capture potential proximal influences on the ankle and leg.
The leg is formed by the tibia and fibula (Fig. 9-1). A normal anatomic relationship between the tibia and fibula is required for proper biomechanics of the knee proximally and the ankle and foot distally. These bones function to distribute the weight-bearing forces along the limb, allowing the junction of the distal tibia, fibula, and talus (the ankle mortise) to produce the range of motion (ROM) needed for walking and running (Fig. 9-2).
Long bones of the lower leg and their primary bony landmarks.
Ankle mortise—the articulation formed by the distal articular surface of the tibia and its medial malleolus, the fibula's lateral malleolus, and the talus.
The motions of the subtalar and talocrural joints are described either by their individual single cardinal plane nature (inversion/eversion, dorsiflexion/plantarflexion, or abduction/adduction) or by the composite motions of pronation and supination that occur around an oblique axis. Pronation comprises dorsiflexion, abduction, and eversion, with supination resulting from plantarflexion, adduction, and inversion (see Table 8-1). Closed-chain pronation causes internal tibial rotation, knee flexion, and internal rotation of the hip. Closed-chain supination results in external tibial rotation, knee extension, and external rotation at the hip.
The tibia is the primary weight-bearing bone of the leg. Its slightly concave distal articular surface forms the roof of the ankle mortise; the medial malleolus forms the shallow medial border of the mortise and provides a broad site for the attachment of the deltoid ligaments. Many of the muscles acting on the ankle, foot, and toes originate off the anterolateral and posterior borders of the tibial shaft. The relatively flat anteromedial portion is covered only by skin, predisposing the richly-innervated periosteum to contusions in this area. The periosteum of the tibial shaft may become inflamed at the ...