Diffuse pigmented villonodular synovitis of the knee: a clinical image

Diffuse pigmented villonodular synovitis (DPVS), currently termed diffuse-type tenosynovial giant cell tumor, is a rare, benign but locally aggressive proliferative disorder of the synovium that most commonly affects the knee joint. It is characterized by synovial hypertrophy, hemosiderin deposition, and recurrent joint effusion, often leading to pain, swelling, and progressive functional limitation. Because its symptoms may overlap with degenerative joint diseases, diagnosis is frequently delayed or masked. A 79-year-old male presented with long-standing bilateral knee pain and stiffness, with more severe symptoms on the right side. Clinical and radiographic evaluation demonstrated advanced bilateral knee osteoarthritis with medial tibiofemoral joint space narrowing and osteophyte formation, more pronounced on the right (R>L). Due to disproportionate symptoms and persistent swelling of the right knee, further imaging and histopathological assessment were performed, confirming diffuse pigmented villonodular synovitis. The patient underwent right total knee arthroplasty with extensive synovectomy. Intraoperative findings showed proliferative synovial tissue along with degenerative intra-articular changes. This clinical image highlights the importance of considering synovial proliferative disorders such as DPVS when clinical severity is asymmetric in osteoarthritis and emphasizes the role of combined surgical and pathological evaluation for definitive diagnosis.