Abstract

Background: Anterior cruciate ligament (ACL) injury is a devastating injury that puts an athlete at high risk of suffering from future osteoarthritis. Identification of risk factors and development of ACL prevention programs likely decrease injury risk. Although studies indicate that sagittal plane biomechanical factors contribute to ACL loading mechanisms, it is unlikely that non-contact ACL injuries occur solely via a sagittal plane. Some authors attempt to ascribe a solely sagittal plane injury mechanism to both female and male ACL injuries and attempt to rebuff the concept that knee “valgus” is associated with isolated ACL injury. However, prospective studies that utilize coupled biomechanical and epidemiological approaches demonstrate that frontal knee motions and torques are strong predictors of future noncontact ACL injury risk in female athletes. Video analysis studies also indicate a frontal plane “valgus collapse” mechanism of injury in females. Since the load sharing between knee ligaments is complex, frontal as well as sagittal and transverse plane loading mechanisms likely contribute to noncontact ACL injury events. The purpose of this review is to summarize existing evidence regarding ACL injury mechanisms and to propose that sex-specific mechanisms of ACL injury may occur with females sustaining injuries via a predominantly “valgus collapse” mechanism.

Conclusion: Prevention programs and interventions that only target high risk sagittal plane landing mechanics, especially in the female athlete, are likely to be less effective in the amelioration of the important frontal and transverse plane contributions to ACL injury mechanisms and could seriously hamper ACL injury prevention efforts. Programs that target reduction of high risk valgus and sagittal plane movements will likely prove to be superior for ACL injury prevention.