Localized Pigmented Villonodular Synovitis of the Knee Co-existing with Extra-articular Nodular Synovitis of the Popliteus Tendon Sheath: A Case Report.

Pigmented villonodular synovitis (PVNS) is a rare proliferative disorder affecting the synovial membranes of joints, bursae, and tendons. The knee joint is one of the most common locations for an intra-articular type of PVNS and this is usually of the diffuse type of PVNS or diffuse pigmented villonodular synovitis (DPVNS). DPVNS tends to be more associated with affectation of contiguous structures. We report a case of a localized form of the disease affecting the knee joint coexisting with an extra-articular lesion of the same nature involving the popliteus tendon sheath of the same knee. The clinical condition was managed with a combined surgical approach of arthroscopic marginal excision for the intra-articular lesion and excision biopsy for the extra-articular lesion.