RESUMEN
Localized nodular synovitis is an uncommon entity with different presentations. It is a benign proliferative disorder that originates from a small area of the synovium. This disorder is found most frequently in the tendon sheaths of the small joints of the fingers and toes. We reported here a case of localized nodular synovitis in a 30 years young man who came with complaints of discomfort in the knee joint. Swelling in the infrapatellar region was diagnosed on physical examination. on MR imaging, a solitary ovoid mass lesion was identified in the infrapatellar region involving the infra patellar fat of pad. Mild enhancement within the lesion was observed after administration of intravenous gadolinium. There was mild to moderate joint effusions in the suprapatellar bursa. Mild synovial enhancement was demonstrated. No meniscal or ligament tear was identified. Prospective diagnosis based on MR imaging was localized nodular synovitis.