The underside of the sustentaculum tali has a distinct groove running from posterior to anterior and along which the tendon of the flexor hallucis longus muscle travels into the sole of the foot.
The superior surface of the sustentaculum tali has a facet (middle talar articular surface) for articulation with the corresponding middle facet on the head of the talus.
Anterior and posterior talar articular surfaces are on the superior surface of the calcaneus itself (Fig. 6.98A):