What's going on with ACL injuries in female athletes?
Kylie Oh, freshman at Yale University, tore her anterior cruciate ligament (ACL) four years ago. She later tore her meniscus, and was operated on. It wasn’t long into her first year at university before she was sidelined once again, with another meniscus injury.
“It’s been a journey, for sure,” Kylie says with a rueful laugh. “I’m currently starting playing games again, but we’ll see how that goes.”
Kylie’s is no rare story, particularly for a female athlete. Research shows women are anywhere between two and eight times as likely as men to sustain an ACL injury when playing football. The debate has shot to the forefront of women’s football, after six of the Guardian’s top 20 female footballers ruptured their ACL in the past 12 months (the latest addition being England captain Leah Williamson, who is ruled out of this summer’s World Cup).
In the last 12 months, 10 Women’s Super League (WSL) players have torn their ACL. (This number only refers to those which were publicised by the club - there may have been more.)
To put this into perspective, in the Premier League only four players suffered confirmed ACL injuries last season - despite 22,320 more minutes of football being played by eight more teams.
The below graph demonstrates how regular ACL injuries are in the WSL compared to in the Premier League. Based on the injury rate in the 2022/23 season, it shows that the WSL saw an ACL rupture every 1,188 minutes, a major contrast from every 8,550 minutes in the Premier League. It also shows how many injuries the WSL would have seen were there as many minutes as in the Premier League.
Dr Christina Allen is the chief of Yale Sports Medicine and an orthopaedic physician for US Soccer, both Men’s and Women’s teams. She specialises in complex shoulder and knee injuries, especially with the ACL.
“Every time she cuts and changes direction, or when someone runs into her, I’m like ‘oh god’," she says of Megan Rapinoe, former Ballon D’or winner, USA captain and two-time world champion. Rapinoe has torn her ACL three times, and returned to football each time.
But what has the science told us so far about why women are more susceptible to ACL injury?
Typical research has noted the anatomic differences between the male and female body, while more recent research has studied the impact of hormonal patterns. Dr Allen does not rule out hormonal factors, but says it has come up with “different conclusions, depending on the cycle.”
The hormonal element is hotly contested, with much of the research not deemed thorough enough. Much of it is based on correlations between ACL injuries and certain times on the menstrual cycle, rather than actual measurements of hormone levels.
“My coaches will tell us to be careful when we’re on our cycle, and that we need to track our cycle because there are correlations between injuries and when you’re on your period. Even for me, when I tore my ACL I was actually on my period," says Kylie.
In early 2020, Chelsea Women’s manager Emma Hayes revealed they were using a specialist app to tailor their training programme around the players’ menstrual cycles to try and cut down on injuries. Since 2018, the Chelsea squad has suffered only three ACL injuries - two of which when the player in question was on loan elsewhere.
The debate around hormones will continue for the foreseeable future, but Dr Katherine Kryger of St Mary's University says science and the media should be cautious on the topic.
Dr Kryger says we should be "careful" when discussing the topic as there is a "tendency within research and within the media of being like 'oh, women are so unstable, fragile, because of their anatomy, their hormonal fluctuations' but we haven't proven that is the cause of these injuries.
"Maybe it is the way we're treating women. I'd like to see that changed in people's perceptions of female athletes and women's football in general."
Anatomic differences, on the other hand, are less disputed as a factor.
“Women have proven strength imbalances, their quad-hamstring ratio is not the same as with men. Men just have more muscle bulk in general. So there's definitely a female factor - I don't really think it's necessarily hormonal, I think it’s more anatomic," says Dr Allen.
“Girls are more quad-dominant which puts them at risk for ACL injury, they have a wider pelvis, it’s just a bunch of things that stack the deck.
“You just try to break down the things you can intervene in to reduce that risk. You can’t change someone’s anatomy, and you certainly wouldn’t want to be messing with someone’s menstrual cycle - the jury’s still out on that one.”
Outline of the female and male body. (Credit: Outlinepics.com)
Outline of the female and male body. (Credit: Outlinepics.com)
This is a full diagram of a knee and shows what happens when an ACL is torn.
(Credit: BruceBlaus (Attribution-ShareAlike 4.0 International (CC BY-SA 4.0))
The Posterior Cruciate Ligament is behind the ACL, and can sometimes be torn at the same time.
The kneecap protects the joint and helps bend and straighten the leg.
This is where the menisci are situated; two pieces of cartilage which act as shock absorbers, stabilise the joint and keep knee movement smooth. Meniscus injuries are common at the same time as an ACL injury - Kylie has torn her meniscus twice.
And here is the anterior cruciate ligament (ACL). It stabilises the joint by preventing the lower leg extending too far and limiting how far the knee rotates.
No surprise then, it tears (as seen above) when the lower leg extends too far, or the knee twists significantly.
It often happens when landing badly from a jump, but it can also happen in contact with someone else. ACL injuries are categorised as Grade 1 (partial overstretch), Grade 2 (partial tear) and Grade 3 (complete tear - seen in diagram).
Sex, to whatever extent, plays a part. Yet gender-based differences have received less attention, says Dr Allen.
“Historically, there’s a lot more emphasis on strength and agility with the men than with women, although I think it’s getting better.
“I’ve been with the women’s national team since 2003, and it used to be just ‘go, go, play, play’ when we go on trips. Now it’s: play, practise, strategy, checking nutrition, checking hydration, there’s a lot more emphasis on injury prevention.”
Lower training ages (the amount of time spent with structured, coached training), less research, and worse facilities have been put forward as other gender-related factors behind the higher injury rate. Dr Allen sees them as “cumulative”.
“Training and strengthening, especially balance and plyometrics, weren’t really emphasised. Now they’re emphasised more at the national level, but at grassroots they’re still not.” Dr Allen says more research into training programmes and how to train “smarter, not harder” can help reduce serious knee injuries in professional sport.
In debating potential causes of the higher rate of injury for women, one aspect of a major injury is often sidelined.
With a greater rate of serious sporting injuries among women, naturally, comes a greater rate of injury-related depression.
Research has shown some athletes struggle with post-traumatic stress disorder following an ACL injury. One study showed 42% of patients with an ACL reconstruction met the criteria for major depressive disorder. It found that isolation and a lack of self-worth lead to lower life-satisfaction scores, depression and other mood disturbances.
Kylie speaks about her personal experience below.
Kylie Oh discussing her mental health experience following serious knee injury.
Kylie started playing for Yale University earlier this year, soon before another meniscus injury. (Credit: Gareth Mackay)
Kylie started playing for Yale University earlier this year, soon before another meniscus injury. (Credit: Gareth Mackay)
A study on collegiate athletes with musculoskeletal or concussive injuries - i.e. those in Kylie’s position - found a peak in depressive symptoms in the period soon after the injury, followed by a decrease in symptoms as the return to sport gets closer.
A decrease in ‘endogenous opiates’, which typically produce happiness and comfort and are released during exercise, is a possible cause. Athletes, who may have been training every day, effectively go cold turkey.
Another theory links an athlete’s identity to their sport, as found in Kylie’s experience above. A loss of the sense of identity that comes with an athlete’s sport can lead to a loss of self-worth.
In light of the difficulties, can a serious injury ultimately help build a strong mentality?
“Oh, oh yeah,” is Kylie’s definitive response. “The first one is like ‘oh my God, my life is ending, what am I gonna do?!’ But after a while you realise you’re gonna get through it. In my position, things could be a lot worse. So you learn perspective. But you also learn how to get through something tough.”
But now, it's time for Kylie to return to the sport she loves. A ‘strong and athletic attacker’ according to her coach, he seems tentative in her optimism. It has, as she says, no doubt been a journey both physical and mental.
“If I have to go through another big injury, again, it might be the end. And I've told myself that a lot, because mentally it's really tough having to do all the rehab and the surgery.”
An alternative route for Kylie would be orthopaedics, in which she will be shadowing Dr Allen over the summer. “I feel like I have a strong connection to injuries," she says, “and I want to keep soccer in my life.”
Further research emerges each year relating to causes, treatment, rehab approaches, and nutrition. Modern science is placing a particular emphasis on prevention rather than remedial treatment. But in truth, the risk of an ACL injury is an unavoidable reality for many sportspeople - and particularly women.
Built with Shorthand