Lipoma arborescens-a rare cause of monoarticular knee joint swelling in adolescents-case report

Lipoma Arborescens is a slowly progressive intraarticular lesion of knee characterised by substitution of sub synovial tissue with fat cells and villous transformation of synovium [1]. It is a rare entity with limited literature. We present a case of lipoma arborescens in 17-year-old boy who presented with complaints of mono-articular swelling of left knee for 2 years with history of antecedent trauma. MRI showed frond like masses present in supra and infrapatellar region with high signal intensity on T1W and Intermediate signal intensity on T2W, consistent with fat. He was managed with open synovectomy which showed yellowish white polypoidal and villous masses of adipose tissue. Masses were sent for histopatholgy which showed hypertrophic villous projections of fat lined by synovial cells. Patient became asymptomatic postoperatively and improved functionally.