pigmented villonodular synovitis (PVNS)

A condition of unknown etiology characterized by hyperplasia or excessive villous proliferation of the synovium. The condition may occur in localized or diffuse patterns & is characterized by repeated hemorrhage within a joint. Hemosiderin-laden macrophages give the synovium a pigmented appearance, thus joint aspiration yields brown fluid. On plain radiographs, there is often a joint effusion with preservation of the joint space & bone mineral density. The later stages of the disease produce erosions on both sides of the joint. Magnetic resonance imaging (MRI) shows low signal intensity of hemosiderin on T1 & T2 weighted images.

References

Basic Radiology, Chen MYM, Pope TL & Ott DJ (eds), McGraw Hill, NY 1996