An unusual cause of popliteal cyst

We describe a surgical treatment for popliteal cyst in a 41-year-old woman affected by diffuse pigmented villonodular synovitis (PVNS) of the knee with extra-articular spreading. The treatment consists of an arthroscopic synoviectomy followed immediately by an open removal of the cyst. At 28-month follow-up, the patient is asymptomatic and no evidence of recurrence of PVNS has been seen. We believe that this double surgical approach may reduce the probability of recurrence of PVNS.