Origin Posterior aspect of interosseous membrane, superior 2/3 of medial posterior surface of fibula, superior aspect of posterior surface of tibia, and from intermuscular septum between muscles of posterior compartment and deep transverse septum Insertion Splits into two slips after passing inferior to plantar calcaneonavicular ligament; superficial slip inserts on the tuberosity of the navicular bone and sometimes medial cuneiform; deeper slip divides again into slips inserting on plantar surfaces of metatarsals 2 - 4 and second cuneiform Action Principal invertor of foot; also adducts foot, plantar flexes ankle, and helps to supinate the foot Innervation Tibial nerve (L4, L5) (L4, L5) Arterial Supply Muscular branches of sural, peroneal and posterior tibial arteries