The tibialis posterior muscle lies in the posterior compartment of the leg. Its main action is to flex the ankle (toward the plantar surface or sole of the foot). It also aids in inverting the foot (turning the toes inward.)
The proximal attachment is the tibia, fibular, and interosseus membrane. The distal attachment is the 2nd to 4th metatarsals and navicular, cuneiform, and cuboid bones.
Nerve supply is from the tibial nerve.