Why ACL injuries are more common in women: The hidden hormonal factor
Summary
Indian women are facing a hidden risk of ACL tears—and it’s not just about bad technique or weak muscles. Hormones play a much bigger role than you think
It’s fascinating how different human bodies can be in the ways they function. Having played, watched, and worked in sport, I’ve seen a fair share of my male friends go through serious knee injuries. Of these, an anterior cruciate ligament (ACL) tear is the most dreaded one, with meniscus tears of varying degrees a close second. While an ACL is mostly a sporting injury, it can also strike without any warning. This is due to recurring stress on the ligament which causes it to lose its elasticity. The most common example given is thinking of the ligament as a stretched-out rubber band.
But until I came across a friend’s experience with an ACL tear, the thought that these could be linked to factors that went beyond the trauma, force or a sudden twist during an injury or a movement never crossed the mind. Nupur D’souza, 38, tore her ACL in 2020 during the lockdown while dancing at home. Despite living an active lifestyle in Goa which includes playing frisbee, hiking and regular gym work, she heard the dreaded snap or pop sound that a torn ligament makes.
Srishti Sharma, 28, tore her ACL last year after a fall during rock climbing. The apparel designer from Delhi attempted a “dyno"—a dynamic move that climbers make using momentum to get from one hold to another—when she fell.
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“I latched on to the hold but slipped, and fell on to the mat, but I fell on my right foot and my knee collapsed in and I heard a pop and that’s when I knew the ACL was gone. My medial meniscus was also torn."
When D’souza was diagnosed, her doctor told her about the correlation between estrogen levels and ligament tears, and how this means that women are predisposed when it comes to ACL tears depending on their menstrual cycle. This has, according to research, led to a two-to-six-fold increase in ACL injuries among female athletes compared to men.
Dearth of knowledge
This fact is well known in competitive athletic circles, but isn’t necessarily common knowledge among fitness enthusiasts, leading to a dearth in knowledge about the hows and whys of ACL tears among women. Even Sharma was unaware of this until she spoke with Lounge for this article. She confirmed that when injured, she, very much like D’souza, was in a stage of her cycle where the estrogen levels spike or dip.
“Women get different injuries and respond to treatment differently. If we don’t understand these differences, we’re missing an opportunity to properly prevent and care for women with orthopaedic injuries," writes Melodie Metzger, PhD, in a June 2023 article on Cedar-Sinai’s website, titled ACL Tears in Girls and Women. Metzger is a researcher for the organisation and focuses on the evaluation of orthopaedic reconstructive devices and techniques.
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It is important to remember here that the ACL is the focus of most ligament injury research because of how common it is and because of its location and use in most activities. It is also worth knowing that not all ACL injuries in women are hormone related. But estrogen plays a vital role in the metabolism of the muscle and bone mass, and is also essential to muscle repair and functioning and production of the protein which make up the muscle.
How estrogen fluctuates
What is interesting is how estrogen levels affect the ligaments. Both Sharma and D’souza were in phases of their cycles when estrogen levels can fluctuate suddenly and can have an impact on the body. “Once I was told of this, I calculated and found out that the injury happened between the 14th and 18th day of my cycle. For most women, estrogen levels peak on the 14th day and then sharply decline," says D’souza, who is an educator and continues to be physically active after a full recovery from her injuries.
While this varies from person to person, the science says that “at days 1-6 of the menstrual cycle, levels of estradiol and progesterone are at their lowest, with estradiol concentration peaking at days 12-14, just prior to ovulation." This is according to a 2022 study titled The Effect of Estrogen on Anterior Cruciate Ligament Structure and Function: A Systematic Review, worked on by Cardiff University School of Biosciences.
Lounge spoke with Vadodara-based orthopaedic surgeon Sriram Sundararajan to try and understand the subtle shifts in ligament health due to estrogen, in as simple terms as possible. It all comes down to another ingredient, which interestingly, is also a huge part of the beauty and skin care industry these days: collagen.
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“Tendons and ligaments are made up of collagen—the predominant one being type one collagen. Estrogen is directly responsible in this collagen synthesis, and hence vital for tendons and ligaments," says Sundararajan. He explains that it is important to understand the structure of ligaments and tendons. Ligaments are a taut structure and the tendons can stretch a bit more than them, so they’re a little less strong. Sinew is what gives strength to ligaments and tendons. “And this happens due to the crosslinking of collagen and is majorly because of an enzyme which—here’s the catch—is inhibited by estrogen. So estrogen is actually responsible for weakening of the ligament and the tendon. This weakening means that the ligaments won’t be as taut as they’re supposed to be during a spike in this hormone and hence the predisposition to injuries," says Sundararajan.
It almost seems like there is no way out for women in this situation, possessing a vital hormone that can also undo their knees. Sundararajan says that some studies have proved that the knee can get lax up to 2-4mm during an estrogen spike. “The effect a spike has on the tendons is relaxing them and that can actually be beneficial because a relaxed tendon means less work for the muscle. But the problem is that this relaxation decreases the stiffness of the ligament—and that means a higher chance of a rupture."
This is the reason why competitive athletes get on oral contraceptives (that help in balancing the levels of estrogen) if they have an event coming up that coincides with the days that their estrogen levels spike. The risk for injury otherwise, is too high.
Strengthen the muscles
But for those who play a sport as part of leading an active lifestyle, the solution would be to try and avoid explosive moves during this phase of the cycle. The focus instead could be on strengthening the muscles around the knee—working on the quadriceps, on the adductors, on the calves and tibialis and the hamstrings and glutes.
This could be the only way, because, as Sundararajan says, there is no way to make a ligament stronger. “The strength of a ligament is not in your control—it is what it is. So strengthen the muscles around these joints. So when you land awkwardly—or take force—the muscles are strong enough to take the trauma, meaning the ligament does not snap easily."
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Both D’souza and Sharma have gone through the gruelling journey of ACL rehabilitation. Athletes always describe it as learning how to walk again. It might very well have been the case that those injuries would have happened irrespective of estrogen levels. However there needs to be greater awareness and research on this subject so that a woman does not have to go through an injury to know about the correlation between their menstrual cycle and the chances of getting a serious knee injury.
This means the entire fitness community, from trainers to coaches to influencers online, need to talk about this freely.
Pulasta Dhar is a football commentator and writer.
