Atypical Presentation of Pigmented Villonodular Synovitis: A Case Report.

Pigmented villonodular synovitis is a rare, disabling disease that usually presents in young adults. Here, the authors present a unique case of pigmented villonodular synovitis in a 60-year-old female diagnosed 20 years after the initial presentation. The patient presented with a complaint of knee pain consistent with osteoarthritis. Radiological investigations, including magnetic resonance imaging, only showed degenerative changes and were inconclusive to diagnose pigmented villonodular synovitis. Intraoperative macroscopic features of the synovium suggested pigmented villonodular synovitis, which was confirmed by histopathological examination. Histopathological examination, despite being the gold standard, was performed late in this case. The authors recommend histopathological confirmation of pigmented villonodular synovitis in all suspected cases, even with inconclusive radiological manifestations.