[Pigmented villonodular synovitis of the knee joint].

Pigmented villonodular synovitis is a rare proliferative disorder of the synovial membrane most frequently found in the knee. The etiopathology of the disease is still not understood. Present terminology differentiates between a localized (LPVNS) and a diffuse (DPVNS) form. Currently, MRI is the diagnostic imaging technique of choice. The localized form (LPVNS) can be cured definitely in almost all cases by partial arthroscopic synovectomy, whereas the treatment of the diffuse form (DPVNS) is discussed controversially concerning an arthroscopic or total synovectomy by open arthrotomy. We report a case rarely found in the literature of a patient suffering from a diffuse form of PVNS localized in the right knee joint. In this case PVNS acted as a locally aggressive and destructive lesion of immense extent invading femoral, tibial and fibular bone and the whole extending muscular system. We performed a radical synovectomy by open arthrotomy. By implanting a tumor prosthesis we prevented progression of the disease. Apart from adequate diagnosis, we recommend complete and aggressive resection of the affected tissue by performing an open arthrotomy.