[Synovial lipoma arborescens]

Lipoma arborescens is a rare intraarticular lesion of unknown etiology. The disorder usually presents as painless swelling and recurrent joint effusion. It is typically located in the knee (especially the suprapatellar bursa), though it has also been described in other joints. Laboratory test results are normal, as well as aspirated synovial fluid. Synovectomy is curative in most cases. The authors report a review of the literature, highlighting the importance of magnetic resonance imaging in the diagnosis of this pathology. Although it is a rare lesion, synovial lipoma arborescens should be included in the differential diagnosis of patients with a chronic swollen joint or recurrent joint effusions.