Do knee abduction kinematics and kinetics predict future anterior cruciate ligament injury risk? A systematic review and meta-analysis of prospective studies

BACKGROUND: To systematically review the association between knee abduction kinematics and kinetics during weight-bearing activities at baseline and the risk of future anterior cruciate ligament (ACL) injury. METHODS: Systematic review and meta-analysis according to PRISMA guidelines. A search in the databases MEDLINE (PubMed), CINAHL, EMBASE and Scopus was performed. Inclusion criteria were prospective studies including people of any age, assessing baseline knee abduction kinematics and/or kinetics during any weight-bearing activity for the lower extremity in individuals sustaining a future ACL injury and in those who did not. RESULTS: Nine articles were included in this review. Neither 3D knee abduction angle at initial contact (Mean diff: -1.68, 95%CI: − 4.49 to 1.14, ACL injury n = 66, controls n = 1369), peak 3D knee abduction angle (Mean diff: -2.17, 95%CI: − 7.22 to 2.89, ACL injury n = 25, controls n = 563), 2D peak knee abduction angle (Mean diff: -3.25, 95%CI: − 9.86 to 3.36, ACL injury n = 8, controls n = 302), 2D medial knee displacement (cm; Mean diff:: -0.19, 95%CI: − 0,96 to 0.38, ACL injury n = 72, controls n = 967) or peak knee abduction moment (Mean diff:-10.61, 95%CI: - 26.73 to 5.50, ACL injury n = 54, controls n = 1330) predicted future ACL injury. CONCLUSION: Contrary to clinical opinion, our findings indicate that knee abduction kinematics and kinetics during weight-bearing activities may not be risk factors for future ACL injury. Knee abduction of greater magnitude than that observed in the included studies as well as factors other than knee abduction angle or moment, as possible screening measures for knee injury risk should be evaluated in future studies.