Synovial lipomatosis: A rare cause of knee pain in an adolescent female.

Synovial lipomatosis is a benign proliferative disease of the subsynovial adipose which can lead to a variety of presentations. Cases of synovial lipomatosis in children or adolescents are rare. This case report describes an adolescent patient with a rare bilateral presentation of synovial lipomatosis. She had been treated for years prior to her presentation for juvenile idiopathic arthritis. She presented with chronic bilateral knee pain, swelling, and mechanical symptoms. Bilateral MR imaging demonstrated effusions, hypertrophy of the synovium, and polyp-like projections of tissue with the same signal intensity as fat which is pathognomonic for synovial lipomatosis. Arthroscopic synovectomy and extensive debridement of polyp like fat projections of the right knee was performed. Histopathology was consistent with the synovial lipomatosis diagnosis. Postoperatively, the patient was satisfied with her outcome with improved pain relief and function in her right knee.