Localised Pigmented Villonodular Synovitis Presenting As Anterior Knee Pain

We report a case of a 21 years old female who presented with a history of anterior knee pain for previous 3 months. Pain was localized to the anteromedial aspect of the left knee and aggravated by flexion. Clinical examination revealed a 2x2 cm painful lump on the anteromedial aspect of the left medial condyle with no effusion. Magnetic resonance imaging revealed an anterosuperior tear of the medial collateral ligament. The patient subsequently underwent left knee arthroscopic examination. Two yellowish pedunculated masses arising from the anteromedial portion of the synovium were discovered and completely excised. Histopathological examination of the excision biopsy revealed pigmented villonodular synovitis (PVNS) with marked central necrosis. One year post excision, she is well with no signs or symptoms of recurrence. This case highlights an uncommon cause of anterior knee pain. Localized PVNS typically presents with mechanical symptoms, however, pain could arise from pedicle torsion and necrosis.