Synovial lipomatosis of the knee in an adolescent girl.

Synovial lipomatosis is an uncommon intraarticular lesion rarely affecting the pediatric age group. Also known as Lipoma Arborescens (LA), it is characterized by extensive villous proliferation of the synovial membrane and hyperplasia of subsynovial fat. The etiology of this condition remains unknown. It should be considered in the differential diagnosis of refractory chronic joint effusion and synovial swelling around the knee joint. MRI is helpful in the diagnosis of this pathology. Treatment is by arthroscopic excision. We report the findings in a 15-year-old girl who presented with a painful, swollen knee of 4 years duration. She was found to have Synovial Lipomatosis of the knee joint, which was excised arthroscopically. Synovial lipomatosis is a rare diagnosis in childhood. It should be considered in the differential diagnosis of refractory chronic joint effusion and synovial swelling around the knee joint. Magnetic resonance imaging may be helpful in the diagnosis of these cases, but confirmation can only be obtained through histology. The recommended treatment is arthroscopic excision of the lesion. In recurrent cases, open synovectomy may be required.