Origin Posterior aspect of fibular head, upper 1/4 - 1/3 of posterior surface of fibula, middle 1/3 of medial border of tibial shaft, and from posterior surface of a tendinous arch spanning the two sites of bone origin Insertion Eventually unites with the gastrocnemius aponeurosis to form the Achilles tendon, inserting on the middle 1/3 of the posterior calcaneal surface Action Powerful plantar flexor of ankle Innervation Tibial nerve (S1, S2) (S1, S2) Arterial Supply Posterior tibial, peroneal, and sural arteries