Popliteal fossa-centered mass with extension medially at the level of the medial femoral condyle. Medial aspect involves portions of the medial retinaculum as well as the vastus medialis muscle. The proximal medial collateral ligament complex as well as the medial head of the gastrocnemius are involved with the lesion. Part of the mass is inseparable from underlying periosteum in the posterior medial femoral epicondylar region.
Patchy osteopenia of the osseous structures, likely secondary to disuse. Small knee effusion is present.