What is the Tibialis Posterior?
The tibialis posterior is a deep muscle in your lower leg that plays a big role in how your foot and ankle handle force when you walk, run, jump, and lift. It starts along the back of the tibia and fibula and the strong membrane between them, then becomes a tendon that runs behind the inside ankle bone. From there it attaches to several bones on the inside of the foot, including the area around the arch.