'The ACL club'

It happened in an instant, but Leah Williamson seemed to know just how serious it was, the second she fell to the pitch.

The Arsenal stalwart and England women's national football team captain was challenging for a ball in midfield during a match against Manchester United in April when she went down grimacing.

Waving her right arm in the air to alert her team's doctors, Williamson slapped the pitch before laying her head down between her arms, dejected. "This does not look good for the England skipper," a BBC commentator said on the live broadcast.

That same day, more than 300km (200 miles) away in Edinburgh, a similar scene interrupted the final moments of a Scottish Women's Premier League match as Hearts forward Katie Rood went down injured in the 82nd minute.

Williamson and Rood would later confirm what many observers had feared: they were the latest footballers hit by a knee injury that has plagued the women's game for decades.

"Unfortunately the World Cup and Champions League dream is over for me and everyone will think that's the main focus, but it's the day to day of what I'm about to go through that is the most draining of my thoughts," Williamson wrote on social media on April 21.

"I'm sad to say that I've joined the ever-growing ACL club," Rood, a New Zealand international player, also later posted on Instagram.

ACL injuries have dominated headlines ahead of the FIFA Women's World Cup, which kicks off in Australia and New Zealand on July 20, as Williamson, Rood, and scores of other top women footballers – from the Netherlands' Vivianne Miedema to Canadian Janine Beckie, Marie-Antoinette Katoto of France and England's Beth Mead – have been sidelined.

While both male and female athletes can suffer ACL injuries, research has shown that female athletes are at greater risk than their male counterparts – as much as eight times higher, according to some experts. Male athletes also return to sport more quickly than their female counterparts.

The situation has raised questions about why so many top female footballers suffer ACL injuries. It has also spurred a debate about equity in the sport, pushing players to urgently call for greater research and access to the same level of resources and support to cope with the injury as their male counterparts.

"I think the amount of ACL injuries in professional women's soccer over the last two years has just been shocking," US national team forward Christen Press, who has undergone three surgeries after she tore her ACL last year, told ESPN in May.

And according to Press, who was not named in the US World Cup squad amid her rehabilitation, the response would be very different if a similar number of male football stars were being hampered in the same way.

"If this happened on the men's side, we would have immediately seen a reaction of, 'How are we going to solve this and figure this out and make sure that these players are going to be available at the biggest moments of their career?'"

Short for anterior cruciate ligament, an ACL is one of four primary, stabilising ligaments in the knee. "Ligaments are essentially ropes that attach bones together," explained Elizabeth Gardner, an associate professor of orthopaedic surgery and rehabilitation at Yale University in the United States.

The medial collateral ligament and the lateral collateral ligament – MCL and LCL, respectively – are located on each side of the knee and prevent side-to-side movement, while the ACL and its "partner" – the posterior cruciate ligament, or PCL – are in the middle and prevent front-to-back movement of the tibia (shin bone) on the femur (thigh bone).

While an ACL injury can sometimes occur due to contact, Gardner told Al Jazeera that the "code word" in sport is typically "a non-contact injury, or a non-contact pivoting injury".

"When you hear that as a sports medicine doctor," she said, "the first thing that pops into your mind is, 'Well, what's going on with the ACL?' Because that's the ligament that's supposed to prevent the knee from pivoting or rotating."

And in the world of professional football, "when an injury like that happened, you knew instantly", according to Amy Walsh, a former Canadian women's national team player.

"Whether it was a player pivoting by herself in the middle of the field, or her plant leg on a cross, and then collapsing to the ground, and then sometimes with that telltale and just awful pop – that unmistakable noise and then the cries of pain," Walsh told Al Jazeera.

The prospect of being the next player to suffer an ACL injury also hung heavily in the minds of many players, said Walsh, who represented Canada at FIFA Women's World Cups in 1999 and 2007 and at the 2008 Olympic Games in Beijing. "I had teammates who would talk about the fact that they were fearful of it," she said.

"To see it happening to players who you thought were really strong, really robust, like almost untouchable – to see them go down, it definitely impacts a team."

An ACL injury can mean the ligament is partially or completely torn, though partial tears are less frequent, Gardner said. And these tears can happen in several ways, including when an athlete takes a misstep or – as is common in football – makes a sharp change in direction.

"A lot of times it is say, an athlete – whether on attack or defence – they're coming up against another player and they go to change directions, to make a move, and their body goes one way and their knee and their lower leg stays where it was," she said.

"As that knee buckles inwards, the lower leg rotates and that's when you feel that pop," said Gardner. "Most of the time it is a full tear; it is intact until it isn't."

For years, researchers have tried to work out why ACL injuries are so prevalent in women's sport.

Researchers have focused on various biological differences between men and women, such as the fact that women generally have a wider pelvis than men, which can affect the movement of the tibia and the femur, or that they have a smaller notch where the ACL attaches to the femur, which can make them more prone to tearing. Others have said less muscle development in women’s hamstrings and glutes means they place more stress on their ACLs when they land after a jump, increasing their risk of injury.

Some studies have looked at what effects players' kits could be having on injuries, notably that some women wear football boots designed for men. Hormone fluctuations and how they can affect female athletes – particularly during their menstrual cycles – have also emerged as a growing area of research.

For example, in the leadup to the 2019 FIFA Women's World Cup in France, the US national team began tracking its players' cycles to try to tailor their training, sleep and nutrition, and make their tournament preparations more efficient. "I feel like it's one of many strategies that we deployed that helped us win," Dawn Scott, then the team's high-performance coach, told Good Morning America at the time.

And in early 2020, Chelsea FC also started tracking the menstrual cycles of its female players in what the British club said was an effort to improve performance and mitigate the risk of injuries – namely to ACLs. "It comes from a place of wanting to know more about ourselves and understanding how we can improve our performance," said Chelsea women's team Manager Emma Hayes.

Ali Monajati, a professor at the University of East London and expert on ACL injuries in elite women's football, said there is some evidence that shows the risk of injury can fluctuate during different phases of a player's menstrual cycle.

Researchers say that hormonal fluctuations during the menstrual cycle affect laxity of tendons and ligaments, strength and neuromuscular control.

"But the biggest problem at the moment, which I can blame partly [on] the governing bodies in sport – whether the federations or UEFA or FIFA – is that we don't have any big data [set] in this area," he told Al Jazeera.

Most of the research done on ACL injuries has not focused on top-level female players, Monajati explained, and as a result it may not take into account specific conditions in the professional women's game, such as stress and workload.

Many experts have pointed to the increased "professionalisation" of women's football – including busier training schedules and more league and international matches – as a potential factor in increased injury risk at the highest levels of the sport.

"The accumulation of fatigue may play a far more important role for those injuries than [among players] who play in the tier-two, tier-three football clubs," Monajati said.

But without the necessary data, he said that figuring out how much each risk contributes to multifactorial ACL injuries among professional women's footballers remains difficult – as does crafting an injury prevention strategy that will be tailored to each player's needs.

For Lyndon Wood, it started with a feeling that something was wrong.

Wood was in her junior year of studies at Wake Forest University in the US state of North Carolina in 2021 and 2022, and her Division 1 football team was averaging an ACL tear every three months.

"It was heartbreaking to see these girls drop like flies," she recalled.

And so Wood – who graduated in May with a degree in biology and plans to attend Johns Hopkins University for graduate school in the fall – began digging into what was happening.

"Most of my research prior to this looked at actual mechanics of ACL repairs," she told Al Jazeera. "But I wanted to look at the sports-specific side of it because it has become such a pandemic in the world of women's soccer."

Wood compared ACL tear rates on her team before and after a seven-month pause in athletic competition at Wake Forest during the COVID-19 pandemic, and evaluated potential injury prevention programmes.

She then approached her team's coaching staff with recommendations, and they agreed to implement FIFA's 11+ injury prevention system (PDF), as well as to conduct individual screenings of players' muscular strength to pinpoint potential risks.

"We started doing the warmup regularly. We tested all athletes and those that we found with deficits did additional lifts to target those muscle groups," she said. "And thankfully, since January when we implemented everything, we have not seen any new ACL tears – knock on wood."

Now, she said her goal is to spread awareness among other US college sport programmes about what can be done to minimise the risk of ACL tears, as well as spur a conversation about "the mental toll" that injured athletes are forced to bear.

Wood tore her labrum – the cartilage that lines a hip socket, which typically tears due to overuse – during her junior year at Wake Forest and had a 10-month recovery. "You essentially lose your identity when you get a heartbreaking injury like this," she said.

"I want to help athletes be able to stay on the field so they have every opportunity they can to be out there and work for what they love."

According to Gardner at Yale University, who also serves as the head physician for the school's varsity athletics teams, as experts have learned more about ACL injuries and developed better ways to treat them, the rehabilitation process has actually "gotten longer, not shorter" for many players.

Decades ago, an athlete could expect to return to competition within six months of having ACL surgery, but today, most doctors would recommend at least nine months, she told Al Jazeera.

That's because the risk of suffering a second ACL tear drops dramatically at the nine-month mark; one 2020 study found that athletes under age 25 who returned before that point were three to seven times more likely to get a new ACL injury compared with those who waited. Another widely cited study from 2016 found that, "during the first nine months after surgery ... for every one-month delay in return to sport, the reinjury rate was reduced by 51 percent".

Gardner said part of the reason relates to the surgery that most athletes need to get in order to return to competition. To treat an ACL tear, doctors put a tendon into the knee that will turn into a ligament. While tendons are "another type of rope" between bones, they respond to stress differently than ligaments, and their "ligament-isation" can take about 18 months to two years to fully complete, she said.

"What's particularly cruel in an ACL [injury] is that in a good circumstance, you're actually feeling pretty good for part of this. But you've got your parents, you've got your doctors, you've got your physical therapist, your athletic trainers, everybody saying, 'No not yet, no not yet, no not yet,'" said Gardner.

In response to that psychological stress, she said medical teams are increasingly using what's known as an "ACL Return to Sport after Injury" (ACL-RSI) index, a questionnaire (PDF) that aims to gauge a player's confidence and anxiety levels around returning to competition. "I utilise it early on in the rehab process frankly as a way to acknowledge what's often the elephant in the room," Gardner said.

"Whereas [return to play] used to be looking at all the physical characteristics ... we're now realising that a score on this ACL-RSI is just as predictive of successful return to sport as a lot of these physical factors."

Rianna Jarrett knows better than most just how devastating an ACL injury can be: By the age of 22, the Republic of Ireland international and current Wexford Youths forward had suffered three ACL tears – two to her right knee, and one to her left.

"I was 18, going on 19," she said about the first time it happened. She was going up for a header during an international match with the Irish Under-19s team and a nudge in the back threw her off-balance.

"When I landed, my right knee just kind of buckled underneath me. It was probably one of the sorest things I'd ever felt at that time. I heard the infamous pop," she told Al Jazeera.

Jarrett, now 29, said that while she knew very little about the injury at the time, she had "heard those three letters being thrown around" and was aware that an ACL tear could mean as much as one year of rehabilitation. "When I got the MRI results, it was quite heartbreaking," she said.

But it was her third ACL tear in 2016 – and third rehabilitation process – that was particularly difficult, Jarrett said. "I kind of struggled with, 'Did I want to play football any more? Was it what I wanted? Was it worth it?' And I think I kind of had a battle with myself," she said.

Jarrett said she was asked early on by a coach what she wanted from her recovery, and she said she simply wanted to be able to play football with her brothers and friends. But after a few weeks, her answer changed. "I said, 'No, I want to get back and play at whatever level I'm capable of at this moment in time.'

"It's quite daunting. No matter how many people you have around you, it is quite a lonely experience and a lonely journey," she said. "Ultimately, you're the only one that puts in the work, and you're the only one that can get you to that position where you're back training and back playing."

The rehabilitation process was long and changed daily as she got stronger, from slowly reintroducing movement and building up her quadricep and hamstring – "the support system around the knee" – to biking and straight-line running, to finally getting back on the pitch and following a strength and conditioning programme tailored for her.

"I arguably came back to the highest standards that I ever played at," said Jarrett, who joined Brighton & Hove Albion in the Women's Super League and then the London City Lionesses before returning to play with Wexford Youths in the Irish Women's National League in January following a string of other injuries.

WHAT A NIGHT!! Thank you to all the fans that came out to support last night, and to everyone that tuned it at home 👏🏾 Massive 3 points! Absolutely buzzing to get my first Senior International goal ☘️ Massive thank you to everyone for all your messages and kind words 💚 pic.twitter.com/Dc0PRtDvmH

— Rianna Jarrett (@RiannaJarrett) October 9, 2019

"It was about proving myself right, that I could come back from [the ACL tear]. Not proving anybody else wrong – but proving myself right," Jarrett told Al Jazeera about what kept her going through what she described as "the dark days" of her recovery.

The support of those close to her was also key. "I surrounded myself with people that I trusted and were able to help me. They didn't only put an arm around my shoulder ... but they also gave me the tough love when it was needed," she said.

"It's just important to trust those around you and if you are going through any sort of an injury and you don't trust the resources that you have, then don't be afraid to speak up and ask for better, or go in search of better."

On top of making sure athletes get the physical and psychological support they need, a growing number of voices are calling for more research into the social and environmental conditions that could be playing a role in ACL injuries, too.

Joanne Parsons, an associate professor in the department of physical therapy at the University of Manitoba in Canada, is among them, and she says those factors likely include a lack of resources, support and opportunities geared specifically to women and girls in football.

She pointed to a match in January between Chelsea and Liverpool that was suspended after just six minutes because the pitch was frozen as an example of how environmental factors can contribute to injury risk.

"The men's team would never be exposed to those conditions because they are better resourced," Parsons, who is also a clinical physical therapist, told Al Jazeera.

"And so that is to me a very plain example of how not investing and not providing the same opportunities and the same resources, equipment, and conditions to the women, very much can set them up for an increased injury risk."

She conceded that proving environmental factors are linked to injury is a difficult and even intimidating task, but she said researchers need to tackle it.

"We've done 30 years of research and we've gotten a certain amount of information from that, but we have not decreased the injury rate for girls and women," Parsons said.

"What we've done so far has helped, but it hasn't solved the problem – so we need to think differently."

Alex Culvin agrees. The head of strategy and research for women's football at FIFPRO, a major union for football players around the world, Culvin said that for years, the central question around ACL injuries in the women's game has been: are there more or fewer injuries?

"It's not necessarily the wrong question," she told Al Jazeera, but it "should be combined with probably 10, 20, 30 other questions that relate to the working conditions of professional women footballers".

Among those other questions, Culvin said, should be whether leagues and clubs are ensuring that players have access to "the absolute best support staff", as well as whether they're playing in conditions that are up to professional standards.

"We have a plethora of reports from players around inadequate training facilities, inadequate medical care, inadequate medical checks, physios, the pitches that people play on, the ability of data scientists to be able to adequately analyse the data to reliably say that someone is being overloaded or underloaded," Culvin said.

"This is not for all clubs, but this is, by and large, the experiences that players have – even at very, very top clubs."

But above all else, experts say there needs to be a concerted and collaborative effort to tackle the problem – from the players and their unions, up to club teams and national and international federations.

"It's sort of a time of reckoning when you look at the big names in the women's game who are going to be out of this Women's World Cup, like the Leah Williamsons, like the Beth Meads, like the [Vivianne] Miedemas – the list goes on and on and on," said Walsh, the former Canadian women's team player.

"If the same issue was happening in the men's game, there would be so much money being pumped into research by FIFA in order to get these players back on the field."

FIFA did not provide a comment to Al Jazeera before publication.

In an interview with Optus Sport in May, the governing body's chief women's football officer, Sarai Bareman, said FIFA has been conducting a "female health" research project for 18 months that includes ACL injuries.

"The way female footballers are trained nowadays, it's based very much on data and history in the men's game. So the aim of this project is to really look at female players as women and make sure that their development and the support that we put around them is specific to them," Bareman said.

FIFA Secretary General Fatma Samoura also told the news outlet that several studies have been commissioned on the health of female athletes. "We are embarking on a massive consultation with experts in genetics and medicine regarding also these ACL injuries for the Women's World Cup," Samoura said.

For its part, the Union of European Football Associations (UEFA) told Al Jazeera that it established a Women's Health Expert Panel this year to tackle a range of issues, including – "with high priority" – the ACL situation.

"The panel specifically focuses on identifying and recognising good prevention programmes that already exist or developing new ones," UEFA said in an emailed statement.

"Recovery after an ACL injury, on average, takes much longer for women than for men due to the physiological variations and differences. However, there are still opportunities for improvement in both medical services and the treatment of female football players, as well as specific prevention programmes. And this is exactly where the panel's focus lies."

Monajati at the University of West London said football’s governing bodies should put an ACL injury screening process in place, similar to the one that was created in response to a deadly incident of sudden cardiac arrest on the men's side.

"That doesn't mean the protocol will solve all the issues," Monajati told Al Jazeera, but he said it will increase awareness and the amount of research available. And that, in turn, can help clubs take a data-driven approach to building specialised, injury prevention programmes.

For her part, FIFPRO's Culvin said while "there are pockets of progress" being made on ACL injury research, the work needs to go beyond these decentralised efforts because the problem is so wide-reaching.

"How do we problem-solve on a global, international level, that then can feed into the federations, that can then feed into the leagues?" she asked, stressing that decision-makers also need to make sure that players' voices are at the heart of the conversation.

"It's everybody's responsibility to really continue to raise awareness around this," Culvin said. "But then, I think there's no point in pointing at a problem and saying it exists.

"We know that there's a problem. It's about, how do we better protect the athletes with our solutions that we come up with?"