GLOSSARY

The tibialis posterior is the deepest muscle of the back of the leg, lying between the tibia and fibula, and is the main supporter of the medial longitudinal arch of the foot.

Attachments and Innervation

• Origin: the interosseous membrane and the posterior surfaces of the tibia and fibula.
• Course: behind the medial malleolus in a dedicated groove.
• Insertion: mainly the navicular tuberosity, with slips to the cuneiforms, cuboid, and bases of the second to fourth metatarsals.
• Nerve: the tibial nerve (L4 and L5).

Actions

• Foot inversion: the strongest invertor.
• Ankle plantarflexion.
• Dynamic support of the medial arch: controlling pronation and arch collapse in stance.
• Locking the midfoot joints: creating a rigid lever for push-off.

Clinical Application

• Posterior tibial tendon dysfunction (PTTD): the most common cause of acquired flatfoot in adults, especially overweight middle-aged women, with pain behind the medial malleolus and inability to perform a single-leg heel raise; it is now also called progressive collapsing foot deformity (PCFD).
• “Too many toes” sign: viewed from behind, more toes are visible on the lateral side of the foot.

Relevance to Sport

• Medial tibial stress syndrome (shin splints): traction of the tibialis posterior and soleus on the posteromedial tibia contributes in novice runners and with sudden increases in running volume.
• Exercises: calf raises with a ball between the heels, band inversion, and walking on tiptoe.