Figure 15c. Tarsal tunnel. (a) Drawing of the medial aspect of the ankle shows the course of the tibial nerve (dark gray region) and its terminal branches, the medial and lateral plantar nerves and the calcaneal nerve, in the tarsal tunnel. Light gray region = flexor retinaculum tendon. (b) Transverse 5-12-MHz US scan of the retromalleolar region shows the retinaculum (arrowheads) and tibial nerve (arrow) close to the posterior tibial artery (A) and veins (V). FDL = flexor digitorum longus tendon. (c) Transverse 5-12-MHz US scan of the medial heel shows the medial and lateral plantar nerves (arrows) and calcaneal nerve (arrowhead). A = posterior tibial artery, FHL = flexor hallucis longus tendon, V = posterior tibial vein.