Magnetic resonance imaging evaluation and arthroscopic resection of localized pigmented villonodular synovitis of the knee.

Diagnosis of localized pigmented villonodular synovitis is clinically difficult, and plain radiographs are usually normal. This article presents five patients with localized pigmented villonodular synovitis of the knee. Symptoms suggested a meniscal lesion in three patients and a loose body in two. Magnetic resonance imaging performed prior to arthroscopic resection revealed a preoperative diagnosis of a tumor in all five patients. Magnetic resonance imaging is a valuable clinical tool for the assessment of intra-articular soft-tissue tumors of the knee that may otherwise be misdiagnosed.