Post-traumatic haemorrhagic synovitis of knee mimicking pigmented villonodular synovitis.

To cite: Atik A, Ozyurek S, Sivrioglu AK, et al. BMJ Case Rep Published online: [please include Day Month Year] doi:10.1136/bcr-2013009353 DESCRIPTION A 23-year-old man who had sustained a minor twisting injury 10 days prior, presented with right knee pain and swelling. There was no history of joint problems, infection or bowel problems, nor was there a family history of arthritis. Physical examination showed a large effusion on the right side with lateral joint line tenderness, from which 70 ml of chocolatecoloured, viscous and heavily blood-stained effusion was aspirated (figure 1). His erythrocyte sedimentation rate and the C reactive protein levels were within normal limits. Rheumatoid factor was negative and results of other blood tests, including a clotting screen, were normal. Plain anteroposterior and lateral radiographs of the right knee joint revealed no bony abnormality. To evaluate his symptoms further, a MRI scan of the knee was performed. Axial (figure 2A) and sagittal (figure 2B) proton density weighted fast spin echo images showed significant effusion in the joint. In these sequences, no significant hypointense synovium thickening consistent with the accumulation of haemosiderin was seen. Contrast-enhanced sagittal T1-weighted image (figure 3) showed nodular and diffuse type synovial thickening and enhancement in the suprapatellar recess. On T1-weighted images, the effusion consistent with haemorrhage in the joint was seen in the intermediate signal intensity. In synovium, there were not any no-signal areas consistent with the accumulation of haemosiderin. The diagnosis was made as a