As we learned from the previous blog, female athletes are 2-8 times more likely to tear their ACL than their male counterparts [1]. In this blog, we’ll take a deeper look at unmodifiable factors that affect the injury risk for female athletes. Although we cannot physically change these factors, it’s important to be aware of them so we can mitigate the risk where we can!

Miss the early parts? Check out the links below to catch up!

Blog 1: Overview

Age

The most at risk population for ACL injury are female athletes ages 12 -17 [2] because during this time their bodies are changing dramatically both anatomically and hormonally. Estrogen levels increase, a menstrual cycle begins and the pelvis widens to support the birthing process and child bearing capabilities one day. That is a whole lot to be happening to a 12-17 year old girl! All of that change is new for the body and can have many diverse side effects and that much change in a body is enough to disrupt the system. Take that disrupted system, without preventative training to account for the new set of variables, and throw it onto a soccer field, you can see how increased risks associated with puberty in a woman can be very disadvantageous for an athlete.

Hormones

With so many hormonal and structural changes occurring between the ages of 12-17, this leads into our next factor: the menstrual cycle and the hormonal changes.. Research shows sex hormones such as estrogen, testosterone and relaxin has effects on the ACL, which may play a role in the laxity of the ligament [3, 4, 5].

The hormones in the menstrual cycle influence ACL tear rate by altering the structure of the ACL. For example, relaxin a protein used to relax the uterus, has receptors that help it bind to the ACL decreasing the tensile integrity [3]. Estrogen receptors, which may play a role in joint laxity, have also been found in ACL’s of female athletes [5]. The ACL and many other ligaments in the body are made up of high levels of collagen in order to maintain their structure. This could theoretically increase injury incidence rates of ACL tears during the pre-ovulatory phase spanning 1 to 14 days of the menstrual cycle where sex hormones are more prevalent [6]. Because higher estrogen levels are typically recorded in women during puberty and child bearing years [7], it may be a small factor in the higher incidences of ACL tear in women of those ages, specifically during the teenage years. Although all the hormones involved in normal functioning of the menstrual cycle are the same, there are varying levels of hormones for each woman and for each time frame of life. This means some women will be more susceptible to the effects of hormones on their ACL injury risk.

Imagine stepping onto the soccer field and all of your ligaments are in a laxity phase. Now, I’m certainly not advocating that all women should stop playing sports during the 1-14 days where there is increased estrogen production in the menstrual cycle but with all of these factors contributing to the high incidence of ACL injuries in female athletes it further concludes that ACL injury prevention programs should be in place for all female athletes starting at about age 10. The bottom line is know your risks so you can change your results.

Anatomical Differences

Unfortunately, the anatomical differences in males and females may also lend to increased risk for female athletes. Even after adjusting for proportional differences, the female ACL is smaller in length, cross-sectional area and volume [8], which puts it more at risk under the same conditions as a male athlete. Differences in lower leg alignment such as anterior pelvic tilt, hip anteversion ("twist of the hip") and tibiofemoral angle and quadriceps angle [9, 10] may affect how the female athlete bears different loads when they perform high intensity activities [11].

Photo courtesy of Next Level Rebel

Differences in hip width cause an increased Q angle in women compared to men [12]. The Q angle is the angle measuring for the midpoint of the patella (knee cap) to the ASIS at the front of the hip [13]. It was originally thought that the larger that angle is, the more lateral force on the patella or kneecap, creating more force at the knee. Multiple recent studies that the Q angle alone plays a smaller role than previously thought [14, 13]. Other factors in combination with an increased Q angle, such as differences in lower extremity alignment and tibial plateau puts the knee in many more compromised positions causing more situations to occur where an athlete is susceptible to an ACL tear [15, 16].

A normal Q angle in women is about 17 degrees and a normal Q angle in men is about 14 degrees [14]. A wider Q angle may contribute to Knee Valgus. Knee Valgus is when the knee naturally buckles inward during a load like a squat, and unfortunately through development females are prone to maintaining increased knee valgus [11]. Knee Valgus is very common in women and men alike but because of increased static knee valgus in females, landing in the wrong position can be a lot more detrimental to a female athlete [17]. Women are much more prone to having Knee Valgus because of weak hips, wider Q angle, and being taught to sit like a lady for all of their life.

Photo courtesy of Science Direct

In my experience, most Knee Valgus in men and women occurs because of weak hips, tight ankles, and impaired quad and hamstring function [18]. Many of these are all common dysfunctions of sitting too much and can be corrected by incorporating a proper strength training and corrective exercise program.

Photo courtesy of Light and Glory Fitness

There are a few other structural differences that make women more prone to ACL injury than men like the overall size/shape of the knee, how that relates to the tibial plateau and over pronation at the foot [19, 20].

Check out Part 3: Here!

For more information on these topics, find my book Surviving 7: The Expert’s Guide to ACL Surgery on Amazon.

Jenna Minecci
9x Surgery Survivor/Strength Coach/Author/Athlete
B.S., CPT, CES, PES, FMS, MWod Pro
@Jennactive
jminecci@gmail.com

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Jenna Minecci is a passionate Personal Trainer and Strength Coach dedicated to helping others prevent injury, prepare for surgery and recover exceptionally from any surgery they have. After having 4 ACL reconstructions fail on her as a teenager, she has now had 9 surgeries and counting. Her goal is to educate and empower others facing difficult surgeries and recovery journeys. She currently works at Lifetime Fitness in Atlanta, Georgia where she specializes in Corrective Exercise, Knee Rehabilitation and ACL Injury Prevention.

She is also the author of the book Surviving 7: The Expert’s Guide to ACL Surgery.

Follow Jenna on social media @Jennactive.

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Have more questions about your upcoming surgery? Sign up today for your free personalized pre-op consult with a Orthopedic/Spine Nurse Practitioner or Medical Device Specialist today!

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References

1. Boden, Sheehan. Torg, Hewett. “Noncontact anterior cruciate ligament mechanisms and risk factors.” Sep, 2010. https://insights.ovid.com/pubmed?pmid=20810933

2. Nessler, T., Denney, L., & Sampley, J. (2017, September). ACL Injury Prevention: What Does Research Tell Us? Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5577417/

3. Dragoo, J. L., Lee, R. S., Benhaim, P., Finerman, G. A. M., & Hame, S. L. (2003). Relaxin receptors in the human female anterior cruciate ligament. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/12860548/

4. Shultz, S. J., Schmitz, R. J., Nguyen, A.-D., Chaudhari, A. M., Padua, D. A., McLean, S. G., & Sigward, S. M. (2010). ACL Research Retreat V: an update on ACL injury risk and prevention, March 25-27, 2010, Greensboro, NC. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2938324/

5. Chidi-Ogbolu, N., & Baar, K. (2019, January 15). Effect of Estrogen on Musculoskeletal Performance and Injury Risk. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6341375/

6. Arendt, E. A., Bershadsky, B., & Agel, J. (2002). Periodicity of noncontact anterior cruciate ligament injuries during the menstrual cycle. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/11974671/

7. Shirtcliff, E. A., Dahl, R. E., & Pollak, S. D. (2009). Pubertal development: correspondence between hormonal and physical development. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2727719/

8. Chandrashekar, N., Slauterbeck, J., & Hashemi, J. (2005, October). Sex-based differences in the anthropometric characteristics of the anterior cruciate ligament and its relation to intercondylar notch geometry: a cadaveric study. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/16009992/

9. Nguyen, A.-D., & Shultz, S. J. (2007, July). Sex differences in clinical measures of lower extremity alignment. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/17710908/

10. Hertel, J., Dorfman, J. H., & Braham, R. A. (2004, December 1). Lower extremity malalignments and anterior cruciate ligament injury history. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/24624006/

11. Shultz, S. J., Nguyen, A.-D., & Schmitz, R. J. (2008, March). Differences in lower extremity anatomical and postural characteristics in males and females between maturation groups. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/18383647/

12. Sutton, K. M., & Bullock, J. M. (2013, January). Anterior cruciate ligament rupture: differences between males and females. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/23281470

13. Nguyen, A.-D., Boling, M. C., Levine, B., & Shultz, S. J. (2009, May). Relationships between lower extremity alignment and the quadriceps angle. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2881465/

14. Mohamed, E. E., Useh, U., & Mtshali, B. F. (2012, June). Q-angle, Pelvic width, and Intercondylar notch width as predictors of knee injuries in women soccer players in South Africa. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3462540/

15. Hertel, J., Dorfman, J. H., & Braham, R. A. (2004, December 1). Lower extremity malalignments and anterior cruciate ligament injury history. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3938060/

16. Mizuno, Y., Kumagai, M., Mattessich, S. M., Elias, J. J., Ramrattan, N., Cosgarea, A. J., & Chao, E. Y. S. (2006, January 1). Q‐angle influences tibiofemoral and patellofemoral kinematics. Retrieved from https://onlinelibrary.wiley.com/doi/abs/10.1016/S0736-0266(01)00008-0

17. Department of Orthopaedics. (n.d.). Anterior Cruciate Ligament Rupture: Differences Between... : JAAOS - Journal of the American Academy of Orthopaedic Surgeons. Retrieved from https://journals.lww.com/jaaos/Abstract/2013/01000/Anterior_Cruciate_Ligament_Rupture__Differences.7.aspx

18. Loudon, J. K., Jenkins, W., & Loudon, K. L. (1996). The Relationship Between Static Posture and ACL Injury in Female Athletes. Journal of Orthopaedic & Sports Physical Therapy, 24(2), 91–97. doi: 10.2519/jospt.1996.24.2.91

19. Chappell, J. D., Yu, B., Kirkendall, D. T., & Garrett, W. E. (2002). A comparison of knee kinetics between male and female recreational athletes in stop-jump tasks. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/11912098

20. Huston, L. J., & Wojtys, E. M. (1996). Neuromuscular performance characteristics in elite female athletes. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/8827300