A 16-year-old male had a right elbow contracture after dislocation. The patient underwent supine-position ultrasound-assisted arthroscopic surgery, combining open removal of the posterior oblique ligament with the medial collateral ligament. The elbow joint flexion angle improved from 120 degrees to 145 degrees, and the extension angle improved from -50 degrees to 0 degrees. The patient returned to sports without recurrence of elbow joint contracture three months after surgery. Supine-positioned ultrasound-assisted arthroscopic surgery for elbow joint contracture is a safe and effective technique that eliminates the need for intraoperative position changes and big skin incisions.