Pigmented villonodular synovitis of the knee: computed tomographic appearances.

Five patients with pigmented villonodular synovitis (PVNS) of the knee demonstrate the value of preoperative, contrast medium-enhanced CT scanning. The technique is shown to be particularly useful in locating recurrent lesions and in demonstrating that popliteal and posterior calf masses are due to PVNS affecting the knee joint itself. In two of the five patients PVNS was not considered a possibility before the CT scan, and none had evidence of bone erosion on plain radiographs. In none of the patients was the unenhanced CT scan able to demonstrate evidence of decreased radiolucency due to fat within the tumour or density greater than the adjacent skeletal muscle, indicating haemosiderin deposits.