The ankle is a hinge joint formed by the tibia, the fibula, and the talus. The tibia and fibula act as a mortise, stabilizing the joint while bracing the talus like an inverted cup.

The principal joints of the ankle are the tibiotalar joint, between the tibia and the talus, and the subtalar (talocalcaneal) joint (Fig. 1).

FIGURE 1. Ankle, medial view.

Note the principal landmarks of the ankle: the medial malleolus, the bony prominence at the distal end of the tibia, and the lateral malleolus, at the distal end of the fibula. Lodged under the talus and jutting posteriorly is the calcaneus, or heel bone.

An imaginary line, the longitudinal arch, spans the foot, extending from the calcaneus of the hind foot along the tarsal bones of the midfoot (see cuneiform, navicular, and cuboid bones in Fig. 2) to the forefoot metatarsals and toes. The heads of the metatarsals are palpable in the ball of the foot. In the forefoot, identify the metatarsophalangeal joints, proximal to the webs of the toes, and the PIP and DIP joints of the toes.

FIGURE 2. Ankle, lateral view.

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