What is the Posterior Tibialis?

The tibialis posterior is a calf muscle located in the center of the back of your leg.  It is responsible for making your foot go up and down as well as inverting it.  There's a tendon (fibrous cord) that connects this muscle to the middle of the foot.  The posterior tibial tendon fortifies the arch of the foot and provides stability to the foot & ankle.  Posterior tibial tendonitis results when this tendon becomes torn or overused.  This can lead to flat foot.