Quite the title, huh?
If you have any involvement in the sports science world, you are well aware that females have a higher incidence of ACL tears than males. In fact, women are 3-6 times at a greater risk for tearing their ACL than men. For years, researchers, coaches, athletic trainers, doctors, and professionals alike have been trying to answer the question, “Why?” Perhaps it is the naturally wider hip angle of a female that creates the infamous ‘Q’ angle putting extra pressure on the knee joint. Or maybe it’s the hamstring to quad ratio, perhaps females present with more muscle imbalances and compensations than males. Still, it wouldn’t fully explain the borderline epidemic that has occurred in the world of ACL injuries. Additionally, if tearing the ACL was due to structural factors then theoretically, us as professionals should be able to predict the incidence of injury with fairly accurate results. Yet, we’re missing something. We still see phenomenal female athletes tear their ACL. Athletes that have done all the right things in training, presented with zero knee valgus, have high resistance to fatigue, work tirelessly on midline strength, landing mechanics, proprioceptors, etc. So, what is it then? I’m not sure we’ll ever truly be able to explain the answer to this in black and white, however, there is some very interesting research that has recently presented itself as promising leads on female ACL tears.
As a college athlete at the University of Alabama, I was surrounded by tremendous athletes on a daily basis. Looking back on my time there, the level of professionalism amongst everyone involved in the athletic department was truly remarkable. I remember one athletic trainer saying she was convinced a female on her period had everything to do with when they tore their ACL. So much so, that she had the wild thought of sitting athletes while they were on their period. “WHAT?!” I blurted out. If anyone told me that once a month (that’s 20-25% of my year) I would have to sit out from athletics on the off chance I’d tear my ACL I’d be picketed in the streets at the ridiculousness of the thought. However, with every crazy thought, there is some merit to it. If this athletic trainer who had been working at the university for over 25 years saw 90% of her athletes tear their ACL during that time of the month then maybe she was on to something. Before we ask the question of what we should do during that time of the month, let’s first explore the why behind how the menstrual cycle impacts a female’s chances of tearing her ACL.
The Impact of Hormones
When a female’s body goes through its menstrual phases, there are various hormones that get released at different times. These hormones are designed to prepare the body in case the female gets pregnant. Thanks to our extremely intelligent body, some of these hormones are designed to increase joint laxity so that the hip region can expand in order to carry a baby. These hormones don’t just increase joint laxity at the hips, they increase laxity throughout the entire body (including the knee). Researchers have found that ACL injury has been 2.7 times higher in women whose knee laxity values were more than one standard deviation from the mean. Thus, it would make sense that hormones that increase knee joint laxity would, therefore, put the female at a greater risk for knee injury. These hormones can not only increase joint laxity but also make an impact on muscle sequencing, muscle contraction, and muscle stiffness. Alterations to any of these will also increase the risk for an ACL injury. Some studies went even further into evaluating hormone concentration levels and found that females with 6.0 pg/mL of relaxin (a hormone that causes the cervix to dilate) were putting females four times more likely at risk for an ACL tear. Now, here is the interesting part; What about females taking oral contraceptives? As a refresher, oral contraceptives are used to ‘tame the cycle’ and their purpose is to suppress the release of certain hormones while you are on the pill so that you won’t get pregnant. Ready for the mind-blowing part? One study found that females taking oral contraceptives were 20% less likely to tear their ACL.
Do we buy it?
After reading this information I was equal parts intrigued and equal parts questioning everything I was reading. The data and facts seemed to make so much sense! This is what the athletic trainer I had talked to in Alabama was talking about! However, there are still some major flaws in the research that need to get investigated. For starters, how was ‘joint laxity’ of the knee actually being tested for most of these studies? Researchers were using the Lachman’s test. The Lachman’s test involves a practitioner manually testing for laxity. Some issues that may arise with this test are 1. Laxity is subjectively measured by the practitioner, 2. The temperature of the individual or the environment could make an impact on the perceived laxity of the joint. When determining which part of the menstrual cycle an individual was at, some studies would simply base their conclusion off of a questionnaire as to, “When was the last time you had your period.” Although it is possible to accurately measure if someone is in the follicular, ovulatory, or luteal phase based on when they get their period, it is also possible that someone has inconsistencies in their cycle and will get their period at the ‘wrong time’ in terms of the appropriate time of the cycle. Based on these estimates is when researchers would determine what hormones were present the most during that time. However, some females don’t even ovulate causing the release of fewer hormones, others have inconsistencies that keep certain hormone levels extremely high. Regardless of these inconsistencies, future research should aim to test hormone levels based on urine, saliva, or blood work. Lastly, one of the biggest issues with the statement pertaining to oral contraceptives is that the types of oral contraceptives vary greatly. In fact, some oral contraceptives contain the hormone, estradiol which is said to be at its highest concentration when the incidence of ACL injuries are also highest. Other oral contraceptives instead only contain progesterone which some researchers claim to have the least impact on joint laxity. Future research should work on completing a study comparing the different types of oral contraceptives and their impact on ACL injuries.
Back to the first question, what do you do about playing time during that time of the month?
The answer here is simple. There is nothing we can do, yet. In the future, I see our collective understanding of this injury growing ten-fold. With it, the understanding of regulating hormones will be within our grasp and we will have a better idea of when an athlete is at greater risk of injury. That is what the professional in me says. The former athlete within me says that there is no way I will ever sit on the sidelines just because I have my period. Just like an athlete who has a knee deviation due to genetic structure, I will strengthen my imbalances tirelessly in order to mitigate my risk of injury. As a female, and as an athlete I understood every day I walked on the field that I was putting myself at risk for injury. I willingly accepted this risk and felt confident in my body because I prepared myself in the best way I could for battle. ACL risk will always be out there but with continued research, we can work to grasp a better comprehensive understanding of how to prevent this catastrophic injury from occurring.