A Pain in the Back of the Ankle! Posterior Ankle Impingement.

Posterior ankle impingement (PAI) is the result of bony or soft tissue abnormalities in the posterior region of the ankle directly behind the talus. Os trigonum, an accessory bone resulting from failure of complete mineralization, and the Stieda process, an elongated process of the posterolateral talus, are the most common bony abnormalities. The flexor hallucis longus tendon travels between the posterolateral and posteromedial tubercles of the talus in a fibro-osseous sheath. Here it is subject to tenosynovitis. Repetitive or forceful plantarflexion is the main risk factor for PAI. Management of bony abnormalities is generally surgical, while soft tissue abnormalities can be managed with a combination of activity modification, orthoses, and selected injections.