Lipoma arborescens of the shoulder: magnetic resonance imaging findings.

Lipoma arborescens is a rare intra-articular lesion that typically affects the knee. This condition represents villous lipomatous proliferation of the synovial membrane. The magnetic resonance imaging findings are diagnostic and include a frond-like, fatty synovial mass and associated joint effusion. The authors describe a 90-year-old woman with lipoma arborescens of the shoulder. To the authors' knowledge, lipoma arborescens has not previously been reported in this joint.