Diffuse Pigmented Villonodular Synovitis Discovered During Revision Total Knee Arthroplasty for Aseptic Loosening: A Case Report

Background Pigmented villonodular synovitis (PVNS) following total knee arthroplasty (TKA) is an extremely rare disease, typically reported within 9 years of the first surgery. It is often clinically indistinguishable from polyethylene wear-induced synovitis or aseptic loosening. We report a unique case of diffuse PVNS diagnosed 21 years after primary TKA, suggesting that PVNS may be a potential cause of aseptic loosening. Case presentation A 71-year-old male presented with left knee pain persisting for a year. He had undergone primary TKA 21 years prior and maintained excellent function, allowing for full weight-bearing and unrestricted daily activities, for 20 years postoperatively. After asymptomatic period, the patient presented with edema and swelling of the knee joint, and multiple instances of hemarthrosis were identified via joint aspiration. Radiographic and computed tomography (CT) evaluations suggested aseptic loosening of the tibial component with extensive osteolysis. During revision surgery, diffuse synovial hypertrophy characterized by yellowish-brown papillae was discovered. A complete synovectomy and revision TKA were performed. Histopathological examination confirmed the diagnosis of diffuse PVNS. Conclusions In long-term follow-up after TKA, the rapid progression of aseptic loosening following frequent episodes of hemarthrosis suggests a potential causal relationship. We consider this hemarthrosis to be secondary to PVNS. Therefore, it can be inferred that the onset of PVNS triggered frequent hemarthrosis, which subsequently led to the development of aseptic loosening.