Pigmented Villonodular Synovitis with Gross Extraarticular Extension and Intraarticular Infiltration

Pigmented villonodular synovitis (PVNS) is an unusual condition of unknown etiology. It is divided into localized and diffuse forms. Once diagnosed, treatment usually consists of surgical synovectomy. However, postoperative recurrence of PVNS occurs relatively frequently. This is a case report of a 78-year-old woman who suffered PVNS recurrence in her knee twice. Gross extraarticular extension and intraarticular infiltration is very rare .It is assumed that the lesion that originated in the extraarticular bursa or peritendineum infiltrated the intraarticular site. The patient was recurrence-free at 12 months after the operation, but six months later a few tumors were noted in her knee. The subsequent recurrences were due to incomplete excision of the previous tumors resulting from technical difficulties.