Sonographic anatomy of the ankle.

Ankle sonography is one of the most commonly ordered examinations in the field of osteoarticular imaging, and it requires intimate knowledge of the anatomic structures that make up the joint. For practical purposes, the examination can be divided into four compartments, which are analyzed in this pictorial essay: the anterior compartment, which includes the tibialis anterior, extensor hallucis longus, and extensor digitorum longus tendons; the accessory peroneus tertius tendon; and the extensor retinaculum; the medial compartment (tibialis posterior, flexor digitorum longus, and flexor hallucis longus tendons; the flexor retinaculum; the medial collateral-or deltoid-ligament, and the neurovascular bundle); the lateral compartment (peroneus longus, peroneus brevis, and peroneus quartus tendons; superior and inferior peroneal retinacula, lateral collateral ligament); and the posterior compartment (Achilles tendon, plantaris tendon, Kagar's triangle, superficial, and deep retrocalcaneal bursae). Scanning techniques are briefly described to ensure optimal visualization of the various anatomic structures.