Traumatic and non-traumatic bone marrow edema in ankle MRI: a pictorial essay.

Bone marrow edema (BME) is one of the most common findings on magnetic resonance imaging (MRI) after an ankle injury but can be present even without a history of trauma. This article will provide a systematic overview of the most common disorders in the ankle and foot associated with BME.The presence of BME is an unspecific but sensitive sign of primary pathology and may act as a guide to correct and systematic interpretation of the MR examination. The distribution of BME allows for a determination of the trauma mechanism and a correct assessment of soft tissue injury. The BME pattern following an inversion injury involves the lateral malleolus, the medial part of the talar body, and the medial part of the distal tibia. In other cases, a consideration of the distribution of BME may indicate the mechanism of injury or impingement. Bone in direct contact with a tendon may lead to alterations in the bone marrow signal where BME may indicate tendinopathy or dynamic tendon dysfunction. Changed mechanical forces between bones in coalition may lead to BME. Degenerative changes or minor cartilage damage may lead to subchondral BME. Early avascular necrosis, inflammation, or stress fracture may lead to more diffuse BME; therefore, a detailed medical history is crucial for correct diagnosis.A systematic analysis of BME on MRI can help to determine the trauma mechanism and thus assess soft tissue injuries and help to differentiate between different etiologies of nontraumatic BME.