Pigmented villonodular synovitis (PVNS) is a rare, benign, proliferative disease of the synovial membrane of joints, tendon sheaths, and bursas.

It presents in two forms: diffuse and localized.

The localized form is usually a single pedunculated mass or, less frequently, two or three nodules.

Histologically there is active proliferation of fibroblastic and histiocytic elements, showing macrophagic activity with phagocytosis of blood pigment (hemosiderin) and lipids.