MRI of the knee in diffuse pigmented villonodular synovitis.

Magnetic resonance imaging (MRI) was performed on 11 patients with surgically proven pigmented villonodular synovitis (PVNS) of the knee. PVNS was diagnosed on the basis of presence of hemosiderin, joint effusion, and hyperplastic synovium without significant joint destruction. MRI provided a detailed map of the distribution of the disease within the joint, emphasizing the common occurrence of the disease behind the cruciate ligaments and in synovial cysts in the popliteal fossa. MRI aided in preoperative planning and postoperative follow-up for residual and recurrent disease. Nine additional cases of joint hemorrhage, hemophilia, desmoplastic tumors, and synovial chondromatosis were included to delineate differential diagnostic criteria.