tibialis posterior

Cause of shin splints!
Test by inversion against resistance
Action inversion and plantarflexion of foot
Origin posterior surface of interosseous membrane, the posterior aspect of the tibia inferior to the soleal line, and the posterior surface of the fibula
Insertion tuberosity of the navicular bone; the plantar surfaces of the cuboid and cuneiform bones; and the bases of the 2nd, 3rd, and 4th metatarsals
Innervation Tibial nerve

Lies in the 4th layer of the sole.
Tendon supports the medial longitudinal arch.