Findings: Moderate to large synovial effusion showing villi form synovial proliferation with septations and multiple nodules. Some areas show hemosiderin deposition and other areas subacute hemorrhagic components. Some erosions and bone marrow edema are seen in the posterior lateral femoral condyle. Some bone edema is also seen in the patella. No articular destruction is seen.
A well-defined lesion measuring 3.2 x 4.3 x 3.3 cm, containing variable abnormal signal intensities, is seen along the posterior aspect of the lateral femoral condyle. Cruciate ligaments, menisci and medial collateral ligament are intact.
Impression: Imaging findings are suggestive of pigmented villonodular synovitis, however, possibility of synovial neoplastic process cannot be excluded.