Purpose: To investigate the risks involved in arthroscopic reduction of anterior cruciate ligament avulsion fractures in adults. Type of Study: Retrospective case series. Methods: We retrospectively reviewed the outcome of 17 adults treated arthroscopically for displaced anterior cruciate ligament avulsion fractures. All patients were treated with primary repair of the avulsion fragment using nonabsorbable sutures passed through the ligament base and pulled down through arthroscopically placed drill holes. Patients were evaluated an average of 5.4 years (range, 2 to 9 years) after surgery. Results: Of the 17 patients in this investigation, 9 (53%) had severe difficulty regaining motion postoperatively. Four patients (24%) required multiple arthroscopic debridements for lysis of arthrofibrotic scar tissue around the anterior aspect of the knee, 4 additional patients (24%) required manipulation under anesthesia to help regain motion, and 1 patient declined manipulation despite significant motion complications. An additional 3 patients (18%) required a second arthroscopy for reasons including removal of loose bodies, anterior scar impingement, and removal of hardware. Only 5 patients (29%) progressed through physical therapy uneventfully. Conclusions: Arthroscopic reduction of avulsion fractures of the anterior cruciate ligament was frequently associated with motion complications and often required additional surgical procedures. Adult patients who undergo this procedure should be counseled regarding the increased risk of motion complications.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 18, No 2 (February), 2002: pp 171–176