ACL Injuries in Female Athletes
While nearly seventy thousand anterior cruciate ligament (ACL) injuries happen during athletic activities reported annually in the United States, female athletes have significantly higher ACL injury rates when compared with the male sports (Arendt, 1995), with the difference varied between two to eight times depending on the sport (Huston, Greenfield, & Wojtys, 2000). On the collegiate level, the analysis of NCAA injury data estimates that one out of ten female athletes will have a serious knee injury (Huston et al., 2000). What are some of the reasons women are more prone to experience an ACL injury? While the recent research literature outlines a number of potential risk factors, the following risk factors are outlined in this article: (a) hormones, (b) muscle balance between quadriceps and hamstrings, and (c) effects of bracing.
While hormones, and in particular estrogen fluctuations during the menstrual cycle, are thought to be some of the risk factors associated in ACL injuries among women, (Arendt, 1995; Arendt, Bershadsky, & Age, 2002; Myklebust, Maehlum, Holm, & Bahr, 1998; Slauterbeck et al., 2002), the results of the latest study of Warden, Saxon, Castillo, and Turner (2006) have suggested that estrogen does not have a major direct effect on ligament mechanical properties. Still, a significant majority of the female athletes suffer an ACL injury during the follicular phase (first half) of their menstrual cycle, when estrogen levels are generally at their lowest (Gale, 2002).
Hewett, Myer, & Ford (2006) have attempted to provide an additional insight into another interesting issue relating to ACL injuries dealing with the effects of knee bracing in decreasing the risk of an ACL injury. However, the findings of their study still leave the question unanswered, concluding that it is unknown whether prophylactic bracing can decrease the risk of ACL injury. The more significant outcome of the study, however, is the finding that after the ACL reconstruction surgery, the functional knee bracing worn for one year provided no difference in knee stability, functional testing, subjective knee scores, or range of motion or strength testing (Hewett, et al., 2006). Bearing this in mind, the common practice of prescribing knee bracing after the ACL surgery seems unwarranted. Could it be a solution to the mental aspect of the injury?
What is certain today is the fact that female athletes have less muscular protection of the knee ligaments than same size male athletes playing the same sport (Huston et al., 2000). Another potential risk factor for an ACL injury for females is the greater increase of the quadriceps strength than that of the hamstring strength for females after menarche (first ever menstrual cycle)(Ahmad et al., 2006).
While further studies investigating the potential risk factors for an ACL injury for female athletes are warranted, in the meantime, female athletes and their coaches should devise and implement ACL injury prevention programs emphasizing hamstring strengthening. In addition, the use of a knee brace for knee stability, range of motion, and strength after the ACL reconstructive surgery does not seem to provide additional benefits.
References
Ahmad, C. S, Clark, A. M., Heilmann, N., Schoeb, J. S., Gardner, T. R., & Levine, W. N. (2006). Effect of gender and maturity on quadriceps-to-hamstring strength ratio and anterior cruciate ligament laxity. The American Journal of Sports Medicine, 34(3), 370-375.
Arendt, E. A., Bershadsky B, and Agel J. Periodicity of noncontact anterior cruciate ligament injuries during the menstrual cycle. J Gend Specif Med, 5: 19–26, 2002.
Arendt, E., & Dick, R. (1995). Knee injury patterns among men and women in collegiate basketball and soccer: NCAA data and review of literature. American Journal of Sports Medicine, 23, 694-701.
Gale, T. (2002). Hormonal cycle plays role in female ACL injuries. The Journal of Physical Education, Recreation & Dance, 73(3), 11.
Hewett, T. E., Myer, G. D., & Ford, K. R. (2006). Anterior cruciate ligament injuries in female athletes: Part 1, mechanisms and risk factors. The American Journal of Sports Medicine, 34(2), 299-312.
Huston, L. J., Greenfield, M. L., & Wojtys, E. M. (2000). Anterior cruciate ligament injuries in the female athlete: Potential risk factors. Clinical Orthopedic, 372, 50-63.
Myklebust, G., Maehlum, S., Holm, I., & Bahr, R. (1998). A prospective cohort study of anterior cruciate ligament injuries in elite Norwegian team handball. Scandinavian Journal of Medicine and Science in Sports, 8, 149–153.
Slauterbeck, J. R., Fuzie, S. F., Smith, M. P., Clark, R. J., Xu, K., Starch, D. W., & Hardy, D.M. (2002). The menstrual cycle, sex hormones, and anterior cruciate ligament injury. Journal of Athletic Training, 37, 275–278.
Warden, S. J, Saxon, L. K., Castillo, A. B., & Turner, C. H. (2006). Knee ligament mechanical properties are not influenced by estrogen or its receptors. American Journal of Physiology Endocrinology and Metabolism, 290, 1034-1040.