Risk Factors for Anterior Cruciate Ligament Injury: A Review of the Literature—Part 2: Hormonal, Genetic, Cognitive Function, Previous Injury, and Extrinsic Risk Factors

CONTEXT: Injuries to the anterior cruciate ligament (ACL) are immediately disabling and are associated with long-term consequences, such as posttraumatic osteoarthritis. It is important to have a comprehensive understanding of all possible risk factors for ACL injury to identify individuals who are at risk for future injuries and to provide an appropriate level of counseling and programs for prevention. OBJECTIVE: This review, part 2 of a 2-part series, highlights what is known and still unknown regarding hormonal, genetic, cognitive function, previous injury, and extrinsic risk factors for ACL injury. DATA SOURCES: Studies were identified from MEDLINE (1951–March 2011) using the MeSH terms anterior cruciate ligament, knee injury, and risk factors. The bibliographies of relevant articles and reviews were cross-referenced to complete the search. STUDY SELECTION: Prognostic case-control and prospective cohort study designs to evaluate risk factors for ACL injury were included in this review. RESULTS: A total of 50 case-control and prospective cohort articles were included in parts 1 and 2. Twenty-one focused on hormonal, genetic, cognitive function, previous injury, and extrinsic risk factors. CONCLUSIONS: Several risk factors are associated with increased risk of suffering ACL injury—such as female sex, prior reconstruction of the ACL, and familial predisposition. These risk factors most likely act in combination with the anatomic factors reviewed in part 1 of this series to influence the risk of suffering ACL injury.