Imaging description

The radiographic changes vary with the type of pigmented villonodular synovitis (PVNS), and whether the disease is localized or diffuse, and also on the joint involved (Figures 85.1 and 85.2). Giant cell tumor of the tendon sheath presents radiographically as a soft tissue mass, with or without a well-marginated erosion in the underlying bone. Giant cell tumor of the tendon sheath is rarely imaged with CT or MRI because the diagnosis is often made clinically. In the localized intra-articular type of PVNS the radiographic examination is usually normal. Radiographs of patients with diffuse PVNS may appear normal early in the disease but more commonly they show a large joint effusion. A joint aspiration typically reveals bloody fluid. Bone erosions are more common in joints with a tight capsule such as the hip or elbow (Figure 85.3). In the knee joint, which is the most commonly involved joint with diffuse PVNS, erosions develop late in the disease because the joint capsule is fairly distensible. Bone erosions are most frequently seen in the hip where about 90% of patients have erosions. Erosions are best delineated with CT. CT can sometimes show a lobulated high-attenuation mass surrounding the involved joint. This is attributed to the high hemosiderin content in the abnormal synovium. Periarticular osteopenia and joint space narrowing in diffuse PVNS are rare findings.