A prospective study was designed to determine the impact of surgical timing on postoperative motion and stability following anterior cruciate ligament (ACL) reconstructive surgery. The study population was limited to acute ACL ruptures from downhill skiing undergoing arthroscopic ACL surgery without arthrotomy or surgical intervention for other ligamentous structures; 185 patients were entered into four separate groups based on the time interval from injury to surgery. Motion and stability were tested at multiple time points from the index surgery and adverse events were recorded. We found no statistical difference in restoration of extension or flexion in any group at any time point. KT-1000 data at 12 months showed a side-to-side difference of < or = 3 mm in 94%, with 6% showing a side-to-side difference of > 3 and < or = 5 mm. We conclude that, in this population, by using modern arthroscopic surgical techniques and an aggressive postoperative physical therapy protocol, motion and stability can be restored in a high percentage of patients and that surgical success is independent of the timing of surgery.