Klippel-Trenaunay-Weber syndrome (KTWS) is a vascular disorder that has significant arteriovenous malformation (AVM). We report a case of an AVM in the suprapatellar fat pad of the knee in a patient with the characteristic manifestations of KTWS, including cutaneous hemangioma, limb hypertrophy, and varicose veins. Magnetic resonance imaging, color Doppler sonography, and subsequent angiography demonstrated an AVM in the supra-patellar fat pad of the right knee causing painful swelling of the knee.