Diffuse PVNS is a benign, proliferative disorder of the synovium with a distinctive complex nodular appearance on MRI. It is most common in the knee, where it presents with recurrent effusions, often for years before the diagnosis is made. Diffuse PVNS is difficult to eradicate completely with surgery; therefore, radiation is sometimes used to reduce the risk of recurrence.
Average age: 35 years
Long history of symptoms, often spanning years
When in the knee, mildly painful, recurrent effusions
Monoarticular, synovial tumor
Distribution: knee, 50%; hip, 20% to 25%; ankle, 10%
Large effusion on T2 with thick, nodular synovium
Heterogeneous T2 low signal due to fibrosis and hemosiderin
“Blooming” on gradient echo sequences due to hemosiderin
Lateral radiograph of the knee demonstrates suprapatellar fullness, typical of diffuse PVNS ( left ). Significant bone erosion on radiographs is uncommon in knee PVNS.
The pigmented, villonodular appearance of the tumor is distinctive on arthroscopy ( right ).
Sagittal T2 MRI shows a large, intraarticular nodular tumor involving both the anterior and posterior joint ( left ). Note the small foci of bone erosion in the proximal tibia.
In advanced disease, the tumor can extend into contiguous bursal spaces, such as the gastrocnemius-semimembranosus bursa ( arrow ), as seen on this sagittal T1 MRI ( right ).