MRI appearance of presumed self-inflicted trauma in the knees of military recruits

When knee bone marrow edema is observed on magnetic resonance imaging (MRI), it usually follows a pattern that can be explained by certain etiologies. This article describes a series of unusual knee bone marrow edemas in soldiers presumed to represent self-inflicted trauma. Ten soldiers (9 men and 1 woman; age range, 19-24 years) underwent knee MRI. None reported recent trauma or stress, and all presented with nonspecific pain or failure to respond to therapy. All showed a similar unusual pattern of bone marrow edema in the medial femoral condyle. Three observers evaluated the location of the bone marrow edema within the medial femoral condyle and its distance from the articular surface, dimensions, overlying soft tissue abnormality, and internal derangements. The edema was always subcortical and located in the middle aspect (n=7) or mid-anterior aspect (n=3) of the medial femoral condyle but was never centered subarticularly. Edema size ranged between 8x10x8 and 32x46x40 mm. Overlying soft tissue abnormalities were common (n=4) and included organizing (n=1) and residual hematoma (n=3). Concomitant MRI abnormalities were seen in 3 patients, usually minor. Eight patients reported longstanding pain with no antecedent trauma, and 2 reported remote trauma. One patient had a negative 4-month follow-up MRI, and another had a negative arthroscopy. Poor correlation existed between MRI findings and the absence of stress and trauma. Soldier chat rooms were found that describe how to induce fractures at this location.