Lipoma arborescens (LA) is a chronic, slowly progressive intra-articular lesion characterized by villous lipomatous proliferation of the synovium. Most cases have been described in elderly patients with degenerative or post-traumatic joint disease, but in several case reports, it has been considered to be related to inflammatory joint diseases. Here, we report a case of 17 years old female firstly presenting with bilateral swelling in both knees of five years duration, followed by the development of wide spread lipoma arborescens associated with the uncontrolled treatment of juvenile idiopathic arthritis.