The posterior tibialis muscle is in the posterior compartment of the leg and is a key stabilizer of the lower leg, aiding in plantarflexion and inversion of the foot as well as arch stabilization. It is innervated by the tibial nerve and supplied by the fibular artery. It originates laterally from the inner posterior border of the fibula and medially from the interosseous membrane and posterior tibia below the soleal line. Olewnik (2019) reports variation of four different attachment sites based on anatomical dissection performed on 80 cadavers (50:50 female to male):

-Most common is type III (43.75%): triple distal attachment with main tendon inserting to the navicular and medial cuneiform bones, with two accessory bands going to the medial, lateral, or intermediate cuneiform bones or to the metatarsal bones (II, III, IV, V).

-Second most common was type II (22.5%): a double distal attachment.

-Type IV (17.50%): quadruple distal attachment.

-Type I (16.25%): single band with insertion to the navicular and medial cuneiform bones.

A likely factor is the anatomical acute turn the tendon makes around the medial malleolus. The two other tendons that accompany the PTT through the tarsal tunnel, flexor digitorum longus and flexor hallucis longus, lack the acute angle. The three tendons accompany the posterior tibial artery and nerve deep to the flexor retinaculum and are commonly remembered by the mnemonic Tom, Dick, and Harry.

Diagnosis is made by a good history and tenderness inferior to the medial malleolus with possible dysfunction of foot inversion and/or plantarflexion. There may be accompanying pes planus and a positive “too many toes” sign.

Ultrasound is used to confirm diagnosis and grade the strain. Treatment includes conservative measures, PT, orthotics, or surgery with an expected recovery time of six to eight weeks.

Olewnik, L. (2019). A proposal for a new classification for the tendon of insertion of tibialis posterior. Clinical Anatomy, 2019 May; Vol. 32 (4), pp. 557-565. DOI: 10.1002/ca23350.