CONTEXT: Reconstruction of the anterior cruciate ligament (ACL) is one of the most common surgical procedures, with more than 200,000 ACL tears occurring annually. Although primary ACL reconstruction is a successful operation, success rates still range from 75% to 97%. Consequently, several thousand revision ACL reconstructions are performed annually and are unfortunately associated with inferior clinical outcomes when compared with primary reconstructions. EVIDENCE ACQUISITION: Data were obtained from peer-reviewed literature through a search of the PubMed database (1988-2013) as well as from textbook chapters and surgical technique papers. STUDY DESIGN: Clinical review. LEVEL OF EVIDENCE: Level 4. RESULTS: The clinical outcomes after revision ACL reconstruction are largely based on level IV case series. Much of the existing literature is heterogenous with regard to patient populations, primary and revision surgical techniques, concomitant ligamentous injuries, and additional procedures performed at the time of the revision, which limits generalizability. Nevertheless, there is a general consensus that the outcomes for revision ACL reconstruction are inferior to primary reconstruction. CONCLUSION: Excellent results can be achieved with regard to graft stability, return to play, and functional knee instability but are generally inferior to primary ACL reconstruction. A staged approach with autograft reconstruction is recommended in any circumstance in which a single-stage approach results in suboptimal graft selection, tunnel position, graft fixation, or biological milieu for tendon-bone healing. STRENGTH-OF-RECOMMENDATION TAXONOMY SORT: GOOD RESULTS MAY STILL BE ACHIEVED WITH REGARD TO GRAFT STABILITY, RETURN TO PLAY, AND FUNCTIONAL KNEE INSTABILITY, BUT RESULTS ARE GENERALLY INFERIOR TO PRIMARY ACL RECONSTRUCTION: Level B.
