The list reads like a who's who of international women's soccer. There's the England duo of Leah Williamson and Beth Mead. Dutch star Vivianne Miedema is also included, as are France's Marie-Antoinette Katoto, Canada's Janine Beckie, and the American pair of Christen Press and Catarina Macario.

What do they have in common? They all will miss the 2023 Women's World Cup with the dreaded torn anterior cruciate ligament. Two other players, Australia's Ellie Carpenter and Spain's Ballon d'Or winner Alexia Putellas, made it back in time for the tournament after suffering the same injury, but with so many talented players missing, the spate of injuries is casting a pall over the tournament.

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"I think the amount of ACL injuries in professional women's soccer in the last two years has just been shocking," Press said during a recent interview on ESPN's Futbol Americas. "And I think if the caliber of players from Beth Mead to Miedema to Alexia [Putellas], in every league; international players doing double duty, stars. ... If this happened on the men's side, we would've 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."

The medical community has long known that women athletes tear ACLs at a rate two to eight times more often than their male counterparts. The results of most studies fall between four to six times. According to a paper published in the Journal of Orthopedics and Orthopedic Surgery, one in 19 women soccer players tear an ACL.

As for why, there are multiple factors at play. Dr. Holly Silvers-Granelli has a Ph.D. in biomechanics and applied physiology, is the owner of Velocity Physical Therapy in Santa Clara, California, and is the chair of MLS' Medical Assessment Research Committee. Silvers Granelli points to six perceived risk factors -- emphasis on "perceived" -- that can explain why women soccer players tear their ACLs more often than men.

One factor is the physiological differences between men and women. In women, the ACL tends to be smaller, and the notch in the femur that the ACL passes through tends to be narrower. That leaves less room for the ACL to move, which means a greater likelihood of impingement on the ACL, and thus more risk of injury.

The second risk factor has to do with environmental factors -- grass vs. artificial turf, temperature, precipitation, choice of cleat be it molded or studded. It's worth noting that only in the past seven years have manufacturers started to produce cleats specifically designed for women.

A third is tied to hormonal surges during a woman's menstrual cycle, which affects the laxity or looseness of ligaments. A fourth risk factor is genetics in that if a parent tears an ACL, their child is more likely to do the same, though that could be down to an athletic parent exposing their child to sports. A fifth is equal access to resources such as quality facilities and knowledgeable coaches and training staff. The last is biomechanics: how an athlete runs, jumps, cuts, etc.

The first factor is what Silvers-Granelli calls "non-modifiable" in that there's little that can be done to undo millions of years of human evolution. The same goes for genetics. The rest, however, are what make solving the ACL problem something of a moving target. When asked if there was one factor that contributed more than others Silvers-Granelli said, "If this were a Venn diagram, it would look like a scatter plot" with little to no overlap.

Where's the research? 'We did it 20 years ago'

For Silvers-Granelli, the biomechanical aspect -- including the tendency for females to have a muscle imbalance between quads and glutes/hamstrings -- qualifies as the low-hanging fruit in ACL injury mitigation. In 2000, Silvers-Granelli was part of a group that developed one of the first PEP Programs (Prevent Injury, Enhance Performance), which comprised a 15-minute dynamic warmup -- without the ball -- of exercises designed to improve strength, balance, jumping technique, etc. The program was tried on 14- to 18-year-olds in Southern California. The results were staggering, including an 88% drop in ACL injuries.

"I was stunned because we were thinking maybe like 35%, 40% hypothetically," Silvers-Granelli said.

As the group was naturally suspicious of a statistical blip, the program was repeated the next year. That group recorded a 72% drop from the baseline. Those results drew interest from the Center for Disease Control, and the program was tried out on 61 NCAA women's soccer teams. That morphed into a 2005 trip to Norway, and the subsequent study in handball players saw a 45% reduction in ACL injuries. This eventually turned into the FIFA 11+ program, which was adopted for men's teams too, with similar results.

"That's the irony of what's happening right now," Silvers-Granelli said. "When everyone's clamoring, 'Where's the research?' I'm like, 'We did it 20 years ago.'" She added, "I'm not saying we solved this 20 years ago, and no other work needs to be done. I'm just saying, 'Look, if the dam's been breached, we have a pretty good patch. So let's start there.'"

Silvers-Granelli is also in favor of what she calls "movement diversity" as a way of combating the tendency of young athletes to overspecialize at an early age. A wider variety of sports and activities will help aid in the coordination and strength of the entire body, rather than one set of muscles.

"There's less bike riding, less skateboarding, less scootering, less playground play and less street play," she said. "There is a lack of proficiency just because kids just do not do that as much as they did."

Silvers-Granelli hesitates to call what's currently going on with ACL injuries an epidemic. She points out that there are more playing opportunities for women than there were 15-20 years ago due to more women's leagues becoming professional. It stands to reason that with more opportunities, more practices and more games there will be more ACL injuries. But progress seems uneven. Silvers-Granelli recounted how one major NCAA women's program recently suffered 22 ACL injuries over a four-year span. Another Division I program, Wake Forest, saw six women's soccer players tear ACLs during the 2021-22 season.

Twin obstacles of compliance and access

Why are ACL injuries in women still so much of a problem?

One factor is what is referred to in the medical community as "compliance," otherwise known as convincing coaches that a dynamic warmup (aka "moving while you stretch") is worth doing. The tools might be out there, but they're not always being implemented by managers. And if they are, they aren't being used enough even though it's free and requires no additional equipment. The bare minimum for using a dynamic warmup is two times a week, though four to five sessions are considered ideal.

Dr. Rachel Frank is a Denver-based orthopedic surgeon who estimates she does "a couple of hundred" ACL reconstructions per year, and is also the team orthopedist for the Colorado Rapids. She said convincing coaches to implement such programs is a huge obstacle to reducing the number of ACL tears.

"You can advise a prevention program and teach [a dynamic warmup] as much as possible, but we've got to get people to do it, and it can't be just going through the motions," she said. "It can't be five minutes of running around the field doing some single leg hops and calling that a prevention program. It's got to be time and dedicated effort. And I think in 2023, time is a commodity, and if a training session for a team is 90 minutes, 20 to 30 of those minutes need to be focused on this prevention program, dynamic warmup, etc."

Lack of available practice time is often offered up by coaches as the main reason more teams don't implement a dynamic warmup, even though at 15 minutes, it's not cutting that much into training time. Coaches prize contact with the ball, and the dynamic warmup would cut into that, so the thinking goes. Silvers-Granelli also noted in her work with MLS teams, performance staff can become "a bit territorial" when it comes to such things as warmup routines.

The resistance seems mystifying. The more players stay healthy, the better the odds are of winning on the field, and coaches are ultimately judged on wins and losses. But access to resources, from both a socioeconomic and gender perspective, can also play a part. That goes for equipment, quality facilities and access to educated training staff.

As news of Leah Williamson's World-Cup-ending ACL injury breaks, the words of her England team-mate @BMeado9 have never rung truer.

More. Research. Needed.pic.twitter.com/0fnCLgCECo

— FIFPRO (@FIFPRO) April 21, 2023

"I think that having access to not just equipment and facilities but to the training for these programs, the neuromuscular prevention programs, etc., is so critical," Frank said. "And unfortunately, there's a lot of disparities, particularly in our lower income and lower resource environments. That being said, these programs are quite easy to learn and teach, and they don't require that much with respect to equipment. And so if we can get the word out, even to those communities where access may be a problem, we may be able to have an impact."

Silvers-Granelli highlighted how at the collegiate level, a private university might have 12 physical therapists for non-revenue sports, while a public school might have one, and that one is usually less experienced. There are other moving parts as well.

"Are people reliant upon insurance coverage? Do they only get 12 or 24 visits? There's so many interesting variables here," she said. "So that's hard to tease out. But we know the recurrence rate tends to be higher in women. But again, is that due to an expertise, resources issue?"

The gender perspective can manifest itself in ways beyond economics. Culture can play a part as well. Silvers-Granelli recently received a text from a colleague at a youth tournament. This player recounted a team's director of coaching, in reference to a player tearing an ACL, saying, "It's OK, [the team] is deep." That speaks to an acceptance in some quarters that this is just something that happens to women players, and seems to gloss over both the physical and emotional impact that occurs when a player sustains such an injury.

"That's horrendous," Silvers-Granelli said about the comment. "These are not widget commodities that we're trading here. We cannot normalize the injury because it's not normal."

Jordan Angeli is a former NWSL player who tore an ACL three times during her collegiate and pro career. She has developed an online resource called "The ACL Club," which aims to connect players who tear ACLs with contacts educated in the recovery process.

"It's grueling. It's brutal. It can be depressing," she said about the rehab process. "You play a sport a lot of the time, and you find success in your sport because it's your outlet of creativity, or it's your time to not think about anything else in the world and just be there totally focused on what you're doing and getting better. When that's taken away, you're having to learn how to live a different life because you don't have that outlet. So much of the joy that you find is through the creative aspect of what you could do as an athlete."

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Angeli goes on to describe ACL recovery as "a year rehab" with "no fast button." Press recently revealed that she is about to undergo a fourth surgery, highlighting how there's no guarantee everything will be as it was before.

"The data on return to play after ACL reconstruction is very, very somber," Frank said. "Athletes get back at a rate of 85-90% or more. But if you really look at the data, their ability to get back to the same level of play that they were at prior to the injury is much lower. Even if they're ready and they feel good and they want to get back and they pass the return to play assessments, the data is just discouraging in that a lot of athletes don't get back to the level that they were at before their injury."

The emotional toll it takes is very real, which is why such an injury can't be simply accepted as part of being a woman soccer player's life. There's an economic aspect, too. According to the aforementioned article in the Journal of Orthopedics and Orthopedic Surgery, the cost of surgeries in 2021 "could exceed $650 million annually."

"You should be doing everything you can to make sure nobody has to go through that," Angeli said. That isn't as easy as it sounds, especially given the continued overall lack of investment in the women's side of the sport. This has long been a problem, and while investment is increasing, not every club is the Kansas City Current, which has its own training facility and soon, its own stadium. A FIFPRO-sponsored study of 362 female players at continental championships revealed that 54% didn't receive a pre-tournament medical exam, and 70% didn't receive a pre-tournament ECG. Only 40% viewed themselves as professional soccer players. These are standard on the men's side.

For Dr. Alex Culvin, FIFPRO's head of strategy and research for women's football, the questions around working conditions are "probably the critical one for us at FIFPRO." She notes that when a player suffers an ACL injury, the quality control issues, such as the qualifications of medical staff and the ratio of support staff to players, need to be taken into account.

"What is the duty of care of the clubs? Are they protecting the players' health and safety?" Culvin asked. "So really the question on conditions is such a critical one that it deserves a real explore around it really. That's what we're trying to do at the moment." She added, "The sort of upward trajectory of professionalism and professional obligations on players is not necessarily being met by professional conditions. So players are professional, but has the game professionalized is probably a big question to ask."

Dawn Scott has witnessed such disparities up close. She is the director and vice president of performance, medical and innovation for the NWSL's Washington Spirit. Her career has included stints with the U.S. women's national team, the England women's national team and MLS side Inter Miami. At the Spirit, Scott has put together a performance and medical staff of 14 people, with another three Ph.D.s brought on to provide additional information on women athletes. That compares favorably to what she said she had at Inter Miami, which had nine staff in that area.

But the Spirit are an outlier. When asked what she had observed in terms of staffing levels at other NWSL teams, she said teams usually had two medical and two performance staff members. That's not nearly enough.

"For me, two performance staff is even hard to individualize and manage each individual play," she said. "You're going to have some players who are playing in the majority of your playing time, some who are your impact players who come on and play some of the time, some who are not getting any playing time, and some who are in return to play kind of protocols. So now you've already got four groups of players. That's where most clubs don't have the size of staff where you can support players individually and be bespoke."

Scott added that the research on women athletes needs to continue beyond the biomechanics space. She also lauds the commitment of Spirit owner Michelle Kang, who has funded Scott's department. But it also highlights the lack of investment elsewhere.

"If 'professional' is simply every player is played regardless of how much they're paid, then OK," she said. "But if you scratch below, how are they supported and prepared? I don't know, maybe I'm being controversial, but I'd probably say 70-80% of the teams in the world are not professional."

Some clubs are taking matters into their own hands. The Spirit and Chelsea in England's WSL have been tracking the data around the menstrual cycles of their players. Scott said the Spirit are doing this to mitigate symptoms and help players train better. But Chelsea has done this also in a bid to reduce soft tissue injuries, and has gone so far as to develop an app where players input data about their cycles. The data isn't conclusive but is still worth being examined.

"The starting point is that we are women and, ultimately, we go through something very different to men on a monthly basis," said Chelsea manager Emma Hayes in an interview with the club's website. "We have to have a better understanding of that because our education failed us at school; we didn't get taught about our reproduction systems. It comes from a place of wanting to know more about ourselves and understanding how we can improve our performance."

Yet the attempt to reduce ACL injuries is still happening in patchwork fashion. Some clubs and federations go the extra mile, while others do the bare minimum, all while the demands on the women's game increase with more games and competitions.

"You've changed the schedule to mimic the men, yet you're not giving the female players the same level of resources," said Beckie, who plays professionally with the Portland Thorns, to Reuters. "If you're going to ask an elite athlete [to] play 50 games a season, you've got to provide them top-of-line care."

Silvers-Granelli added, "I think we have to set expectations higher, too. That [an ACL injury] isn't my destiny."

The goal of fewer ACL injuries in the women's game has some clear pathways. Whether there is the necessary will is a different question.