Presentation
Chronic knee pain. No trauma.
Patient Data
There is effusion in the knee joint and its recesses, as well as diffuse, irregular synovial hypertrophy with lobulated contours and villous projections. The changes show intermediate signal on T1WI and T2WI, high signal on STIR and low signal 'blooming' on T2* GRE, suggesting hemosiderin deposition. The hypertrophic changes cause small erosions in the proximal tibia. The findings are most likely in keeping with diffuse form of pigmented villonodular synovitis (PVNS).
Edematous changes in calf muscles are noted.
Case Discussion
The appearance of findings in this case is highly suggestive of pigmented villonodular synovitis. The differential would be haemophilic arthropathy; however, this patient didn't have a bleeding disorder.
The key sequence in this case is T2* GRE, which shows characteristic low-signal 'blooming' and should be performed in equivocal cases.