Diagnosis

Pigmented Villonodular Synovitis (PVNS)

Case Discussion

Pigmented villonodular synovitis (PVNS) is a condition that causes proliferation of joint and tendon synovium. PVNS is divided into two categories: localized (nodular) and diffuse. Localized PVNS occurs in one area of the joint and typically responds well to surgical treatment, whereas diffuse PVNS involves the entire joint and is more difficult to treat.

MRI findings of PVNS include a synovial mass that is low to intermediate signal intensity (similar to that of muscle) on T1-weighted images, and low to intermediate signal intensity on T2-weighted images due the hemosiderin component of the lesion. Some areas may express high signal intensity due to joint fluid or inflamed synovium.

Prominent low signal susceptibility (“blooming”) artifact is noted on gradient echo sequences. Blooming artifact is caused by local magnetic field heterogeneity due to ferromagnetic substances, resulting in marked rapid T1 and T2 relaxation (seen as marked hypointensity).

PVNs is part of the family of synovial metaplasias which includes: villonodular synovitis, synovial chondromatosis, synovial osteochondromatosis, and lipoma arborescens. The standard treatment is synovectomy. However, when disease is extensive, radiation treatment with beta emitters may be used.

Key Images

PVNS of the left ankle in a 56-year-old woman with previous injury to the peroneal tendons, now complaining of chronic foot/ankle pain.

A. Sagittal T1 image of the left ankle shows extensive tumefactive synovial thickening throughout the entire ankle (red arrow). Prominent pressure erosions are present on the dorsal aspect of the talus (green arrow) as well as the upper surface of the sinus tarsi (yellow arrow).
B. Axial T2 image shows low signal tumefactive synovial thickening and foci of prominent low signal susceptibility (red arrow), consistent with hemosiderosis.
C. Axial T2 image shows low signal tumefactive tenosynovial thickening engulfing the peroneal tendons (yellow arrow). 

References

  1. Brien EW, Sacoman DM, Mirra JM. Pigmented villonodular synovitis of the foot and ankle. Foot & Ankle International 2004; 25(12):908-913
  2. Hughes TH, Sartoris DJ, Schweitzer ME, Resnick DL. Pigmented villonodular synovitis: MRI characteristics. Skeletal Radiol 1995; 24(1):7-12