We present the first reported case of acute "wiiitis", documented clinically and by imaging, of the upper extremity, caused by prolonged participation in a physically interactive virtual video-game. Unenhanced magnetic resonance imaging (MRI) demonstrated marked T2-weighted signal abnormality within several muscles of the shoulder and upper arm, without evidence of macroscopic partial- or full-thickness tearing of the muscle or of intramuscular hematoma.