ABSTRACT
Pigmented villonodular synovitis (PVNS) is a rare proliferative disease involving synovial membranes. Natural history and etiology of PVNS are not well known. PVNS presents as localized or diffuse tumor like nodular lesion of the synovial lining of the joint and the synovial spaces adjacent to the joints. Though histologically benign, it is a very aggressive lesion, capable of bone destruction and widespread infiltration of surrounding tissues. Standard therapy is surgical resection, but due to the infiltrative growth, the recurrence rate is significantly high. After several relapses surgical treatment of diffuse PVNS becomes difficult and may require amputation of the involved limb. Radiotherapy can provide an effective treatment option for patients with large lesions or lesions which are not suitable for surgery, after incomplete resection to prevent relapses or to avoid amputation. We report 2 cases of diffuse PVNS in the knee joint treated with arthroscopic gross total synovectomy and radiotherapy.