Presentation
Three months history of painful swelling of the right knee.
Patient Data
The MRI sequences demonstrate a moderate joint effusion with thickening and proliferation of the synovium mainly of the medial/lateral aspect of the suprapatellar recess with enhancement on postcontrast sequences. Multiple confluent nodular masses of various sizes seen mainly in the posterior recess of the knee joint, of low to intermediate signal on T1, high signal on PD fat sat with “blooming artifact" on gradient-echo due to hemosiderin deposition. The postcontrast sequences show moderate and heterogeneous enhancement. No evidence of extrinsic marginal bone erosions seen.
Case Discussion
The patient's age, the clinical presentation, and the MRI features suggest probably a pigmented villonodular synovitis (PVNS).
On imaging, the differential diagnosis should include non-ossified synovial osteochondromatosis and siderotic synovitis.