Pigmented villonodular synovitis. (a) Sagittal multiplanar GRE MR image
(MPGR; GE Healthcare) (400/15; flip angle, 30°; bandwidth, 122 Hz/pixel; voxel
size, 0.51 × 0.67 × 4.0 mm; FOV, 130 × 130 mm) of the
knee joint shows moderate to severe joint effusion and a Baker cyst (arrowhead). Synovium
shows irregular nodular thickening with dark areas of hemosiderin deposition (arrows).
(b) Sagittal contrast-enhanced T1-weighted spin-echo fat-saturated MR image
(Philips) (500/10; flip angle, 90°; bandwidth, 108.5 Hz/ pixel; voxel size,
0.57 × 1.1 × 4 mm; FOV, 220 × 220 mm) shows diffuse
irregular enhancement of the synovium.