Intra-articular Localized Haemangioma of the Knee Mimicking Localized Pigmented Villonodular Synovitis: A Case Report.

Intra-articular synovial haemangioma of the knee is a benign tumour. However, diagnostic delay leads to degenerative changes in the cartilage and osteoarthritis due to recurrent haemarthrosis. Therefore, treatment should be performed immediately. We report the case of a localized synovial haemangioma arising from the medial plica in a 38-year old female presenting with pain and restricted range of motion in the right knee joint. Initially, we diagnosed this case as a localized pigmented villonodular synovitis (LPVS) based on MRI and arthroscopic findings and performed only arthroscopic en bloc excision of the mass and synovectomy around the mass for diagnostic confirmation. Fortunately, there was no difference in the treatment approaches for LPVS and localized haemangioma and the synovial haemangioma had not recurred at the 3-month postoperative follow-up with MRI. The patient's clinical symptoms resolved and had not relapsed two years after surgery.