Fig. 17-7. The facets of the ankle, subtalar, and talocalcaneonavicular joints. A, Diagram of the talus from above to show the three-surfaced trochlea that fits into the mortise formed by the lower ends of the tibia and fibula. B, Diagram of the calcaneus from above to show the posterior facet (P) for the subtalar joint, separated by the canalis and sinus tarsi from the middle (M) and anterior (A) facets of the talocalcaneonavicular joint. The socket of this latter joint is completed by the spring ligament and the concavity of the navicular. C, Diagram of the talus from below to show its corresponding facets for the subtalar and calcaneonavicular joints. Cf. fig. 12-36. A broad arrow in A emphasizes that the head of the talus is directed anteromedially. Click for high resolution image.