Tibialis posterior muscle

The Tibialis posterior is the most central of all the leg muscles.

It is the key stabilising muscle of the lower leg.

Origin and insertion
It originates on the inner posterior borders of the tibia and fibula. It is also attached to the interosseous membrane, which attaches to the tibia and fibula.

The tendon of tibialis posterior the decends down posterior to the medial malleolus and to the plantar surface of the foot where it inserts on to the tuberosity of the navicular, the first and third cuneiforms, the cuboid and the second, third and fourth metatarsals.

Function
As well as being a key muscle for stabilisation, the tibialis posterior muscle also contracts to produce inversion of the foot and assists in the plantar flexion of the foot at the ankle.