Villonodular synovitis

In the localized form a nonpainful soft tissue mass is usually observed, frequently in the digits of the hands and feet. On radiographs, the soft tissue mass is evident and is frequently associated with bone that has well-defined sclerotic margins. A more diffuse pattern of pigmented villonodular synovitis may also occur but is less common and usually involves the larger joints, especially the knee. Extensive haemosiderin deposition and haemorrhagic effusions sometimes are seen. In this form the joint space is usually normal in width and osteoporosis is absent or mild. Extensive haemosiderin deposition may be demonstrable on CT scans as increased attenuation values. MR imaging will also demonstrate the joint effusion, bone erosions and haemosiderin-laden tissue (Fig.1). Many of the radiographic features of diffuse intra-articular pigmented villonodular synovitis are identical to those seen in cases of idiopathic synovial chondromatosis. The presence of calcification, however, generally eliminates the diagnosis of pigmented villonodular synovitis. The radiographic features of pigmented villonodular synovitis are also modified in cases of bursal or tendon sheath involvement, including the nodular variety of tendon sheath disease known as giant cell tumour. With MR imaging, the deposition of haemosiderin in cases of pigmented villonodular synovitis leads to dramatic abnormalities characterized by regions of low signal intensity on both T1- and T2-weighted spin-echo MR images.

DR/RB