STUDY DESIGN: Systematic literature review. OBJECTIVES: To summarize and evaluate research on factors predictive of progression to surgery after nonoperative treatment for an anterior cruciate ligament (ACL) rupture. BACKGROUND: Anterior cruciate ligament rupture is a common injury among young, active individuals. Surgical reconstruction is often required for patients who do not regain satisfactory knee function following nonsurgical rehabilitation. Knowledge of factors that predict the need for surgical reconstruction of the ACL would be helpful to guide the decision-making process in this population. METHODS: A search was performed for studies predicting the need for surgery after nonoperative treatment for ACL rupture in the Embase, MEDLINE (OvidSP), Web of Science, CINAHL, Cochrane Central Register of Controlled Trials, Pub Med, and Google Scholar digital databases from inception to October 2013. Two reviewers independently selected the studies and performed a quality assessment, Best-evidence synthesis was used to summarize the evidence of factors predicting the need for surgical reconstruction after nonoperative treatment for an ACL rupture. RESULTS: Seven studies were included, 3 of which were of high quality. Based on these studies, neither sex (strong evidence) nor the severity of knee joint laxity (moderate evidence) can predict whether, soon after ACL injury, a patient will need ACL reconstruction following nonoperative treatment. All other factors identified in this review either had conflicting or only minimal evidence as to their level of association with the need for surgical reconstruction. Noteworthy is that 1 high-quality study reported that the spherical shape of the femoral condyle was predictive of the need for ACL reconstruction. CONCLUSION: Sex and knee joint laxity tests do not predict the need for ACL reconstruction soon after an ACL rupture. Independent validation in future research will be necessary to establish whether knee shape is a predictive factor.