Diffuse pigmented villonodular synovitis incidentally identified during revision total knee arthroplasty for aseptic loosening: a case report

Pigmented villonodular synovitis (PVNS) occurring after total knee arthroplasty (TKA) is extremely rare and has most commonly been reported within 10 years after the index procedure. Clinically, it can be difficult to distinguish from polyethylene wear–induced synovitis or aseptic loosening. We report a rare case of diffuse PVNS diagnosed 21 years after primary TKA and treated with revision arthroplasty.

A 71-year-old man presented with a one-year history of left knee pain. He had undergone primary TKA 21 years earlier and maintained excellent function with full weight-bearing and unrestricted daily activities for approximately 20 years after surgery. Following this long asymptomatic period, the patient developed knee swelling and recurrent hemarthrosis, which was confirmed on three occasions by joint aspiration.

Radiographic and computed tomography (CT) evaluations suggested aseptic loosening of the tibial component accompanied by extensive osteolysis on the medial side of the proximal tibia. During revision surgery, diffuse synovial hypertrophy characterized by yellowish-brown papillary projections was observed. Complete synovectomy and revision arthroplasty were performed. Histopathological examination subsequently confirmed diffuse PVNS.

We report a rare case of diffuse PVNS confirmed by surgical biopsy during revision arthroplasty performed 21 years after primary TKA, representing an unusually long interval after the index procedure. In patients with TKA presenting with recurrent hemarthrosis and aseptic loosening, PVNS should be considered in the differential diagnosis and may be associated with prosthetic loosening.