Lipoma arborescens (LA) is a rare benign soft tissue tumor characterised by a hyperproliferation of villi and fat cells in the joint synovium. It is most frequently localized in the knee as reported here. This is a case report of a 16-year-old adolescent, affected by type I diabetes mellitus, who reported left knee pain and functional limitation to medical attention. She performed a physical examination, MRI and biopsy using an arthroscopic approach, leading to the LA diagnosis and classification. The LA has been thus treated with an arthroscopic synovectomy, which is the treatment of choice for LA, characterized by a low recurrence rate.
