Anatomy of the Subtalar Joint.

The subtalar joint is divided into the talocalcaneonavicular and the talocalcaneal joint, separated by a conical interosseous tunnel (canalis and sinus tarsi). The talocalcaneonavicular joint is a ball-and-socket articulation (coxa pedis). An important part of the coxa pedis is the spring ligament. The canalis and sinus tarsi are occupied by the roots of the inferior extensor retinaculum, cervical ligament, interosseous talocalcaneal ligament, and anterior talocalcaneal ligament. Three-dimensional motion in the subtalar joint complex (eversion/inversion) is guided by the axial alignment of the talus, calcaneus, and navicular; the ligaments; and the shape of the articular surfaces.