The arthroscopic appearance of lipoma arborescens of the knee.

Lipoma arborescens is a rare intra-articular lesion consisting of a villous lipomatous proliferation of the synovial lining. This case report draws attention to the history, physical findings, and arthroscopic appearance of lipoma arborescens, a rare lesion of the synovial lining of the knee. Arthroscopically, the lesion appears as a synovial lesion with numerous fatty-appearing globules and villous projections. In addition, magnetic resonance imaging is a valuable tool to differentiate the lesion from rheumatoid arthritis, pigmented villonodular synovitis, and synovial chondromatosis in those patients who present with a chronic, swollen, and painful joint.