Baked beans in the knee? An odd-looking synovial swelling in the knee joint.

Lipoma arborescens (LA) is a rare benign neoplasm affecting large synovial joints, most commonly seen in the knee joint. Unlike other common swellings around the knee joint, LA is intra-articular and can lead to degenerative changes in the knee joint due to mechanical impingement. The importance of correct diagnosis with characteristic MR and macroscopic appearance and appropriate surgical treatment is outlined in this case report.