Localized pigmented villonodular synovitis: arthroscopic treatment of a lesion arising from the quadriceps tendon sheath.

Pigmented villonodular synovitis (PVNS) is a rare benign proliferative growth of synovium of obscure etiology with a wide spectrum of clinical presentation. Localized PVNS, also known as giant cell tumor of the tendon sheath, is even more uncommon. Localized PVNS of the knee is a rare, idiopathic condition presenting with symptoms that can mimic other intra-articular pathologies. The condition is usually monoarticular, the knee being the most commonly affected joint. We report a rare case of PVNS arising from the quadriceps tendon sheath. It was successfully treated with arthroscopic intralesional excision. At 18 months' follow-up, there has been no recurrence.