Imaging Features of Pigmented Villonodular Synovitis with Emphasis on Sonographic Findings

Image T: Lateral radiograph of the knee shows subtle soft tissue masses of increased density (arrows) representing hemosiderin-laden synovium and prominent swelling in the region of the suprapatellar bursa consistent with a large effusion.

Image U: Sagittal PD-weighted MR image reveals a joint effusion and lobulated low signal masses in the popliteal fossa and along the posterior margin of the suprapatellar bursa (arrow).

Image V: Sagittal gradient-recalled echo MR image shows intra-articular low signal lobulated masses (arrow) to better advantage than image U. This is particularly evident in the suprapatellar bursa where there is high contrast against the adjacent joint effusion. The masses appear more prominent because the magnetic susceptibility caused by hemosiderin deposition is accentuated in this sequence.

Image W: Sagittal T1-weighted fat-saturated gadolinium-enhanced MR image shows contrast enhancement corresponding to soft-tissue lesions (blue arrows) and thickened synovium. Note small irregular central region of less prominent enhancement (yellow arrow) relating to a region of more concentrated hemosiderin deposition.

Image X: Longitudinal sonogram of the popliteal fossa reveals a nodular mass (between arrows) corresponding to the lesion seen on images U-W. Note the heterogeneous, increased echogenicity.

Image Y: Longitudinal sonographic image of the suprapatellar bursa shows areas of loculated joint effusion with a heterogeneous soft tissue mass (yellow arrows) at the posterior aspect of the bursa. Note the femoral cortex (blue arrows).

Image Z: Longitudinal power Doppler image of the suprapatellar bursa shows markedly increased flow within hyperplastic synovial soft tissue components consistent with hypervascularity.

Image AA: Transverse sonogram of the anterior distal thigh obtained before intraarticular radiation treatment shows marked synovial thickening and soft tissue nodularity occupying and expanding the suprapatellar bursa (arrow). Note several pockets of fluid (asterisks) representing loculated joint effusion.

Image BB: Sonograms obtained after six courses of intraarticular radiation that correlates with image AA shows reduction in size of the synovial masses and near complete resolution of the joint effusion in the suprapatellar bursa.

Calcifications are rare in PVNS. If calcifications are seen, other diagnoses such as synovial osteochondromatosis or synovial sarcoma should be considered.

Intraarticular radiation therapy has been advocated as an effective treatment for PVNS. Sonography may be used to follow the effects of this therapy as illustrated in this case.