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functional anatomy BY CHRISTY CAEL TIBIALIS POSTERIOR The posterior tibialis is the deepest muscle in the posterior low leg. It is located deep to gastrocnemius and soleus, which form the bulk of the calf, and between flexor digitorum longus and flexor hallucis longus. The muscle belly anchors to the TIBIALIS POSTERIOR Actions • Plantar flexes the ankle • Inverts the foot Innervation • Tibial nerve • L4–S1 Attachments • Origin: lateral, posterior tibia, proximal 2/3 of medial fibula, and interosseous membrane tibia, fibula, and the interosseous membrane between the two bones. Inferiorly and medially, the tendon takes a sharp angle through the tarsal tunnel, a space between the medial malleolus and calcaneus that is similar in function to the carpal tunnel of the wrist and hand. The other muscles of the tarsal tunnel include the flexor digitorum longus and flexor hallucis longus. (Hint: to remember this group, think of Tom, tibialis posterior; Dick, flexor digitorum longus; and Harry, flexor hallucis longus. You can also replace the and with N to remind yourself that the posterior tibial nerve also runs through the tunnel.) After passing through the tarsal • Insertion: navicular tuberosity, cuneiforms 1–3, cuboid, and bases of metatarsals 2–4 tunnel, posterior tibialis follows the curve of the medial arch onto the bottom of the foot. There, it spreads like a spiderweb and inserts onto eight separate bones, including the navicular, cuneiforms, and second, third, and fourth metatarsals. This broad insertion provides dynamic support to the medial arch and controls pronation or flattening of the foot. Maintaining a neutral arch is a critical element of healthy posture for the lower extremity. connect with your colleagues on massageprofessionals.com 85