Infrapatellar pigmented villonodular synovitis: arthrographic detection.

An ovoid density was demonstrated by arthrography in the infrapatellar fat pad region of seven patients. In three patients, the density appeared demarcated from the fat pad, and arthrotomy in two of them disclosed a localized pigmented villonodular synovitis. In four patients the density appeared contiguous with the fat pad, and in two of these patients no infrapatellar abnormality was observed at arthrotomy. This arthrographic distinction may provide more specific criteria for the preoperative diagnosis of localized, infrapatellar pigmented villonodular synovitis and thereby prevent overdiagnosis.