Medial Collateral Ligament Complex of the Ankle: MR Imaging Anatomy and Findings in Medial Instability

Ankle ligament injuries are among the most common injuries in sports and recreational activities. Injuries of the medial collateral ligament or deltoid ligament complex account for ∼ 15% of ligamentous ankle trauma. They are usually associated with injuries of the lateral collateral ligaments and the tibiofibular syndesmosis, as well as malleolar fractures. The deltoid ligament complex consists of a superficial and a deep layer. The three main components of the superficial layer are the tibionavicular, tibiospring, and tibiocalcaneal ligaments. The deep layer is composed of the anterior and posterior tibiotalar ligaments; the latter is the strongest ligament of the whole complex. In approximately half of patients, injuries of the superficial layer are associated with a lesion of the posterior tibiotalar ligament (pTTL), whereas in contradistinction most injuries to the pTTL are associated with lesions of the superficial layer. The most common location of injuries to the superficial layer is at the tibial periosteal attachment with partial discontinuity, delamination, or a complete tear with or without lesions of the flexor retinaculum. Lesions of the pTTL are often midsubstance. In chronic lesions a distorted and thickened superficial layer at the tibial insertion with periosteal reaction and bony spurs is usually visible. The scarred pTTL shows loss of normal striation. In chronic stages of pTTL lesions, volume loss is typically seen. Associated periosteal spurs and intraligamentous ossicles are common. In late stages, tibiotalar valgus with osteoarthritic changes of the ankle will develop.