DENVER — Research shows that female athletes are more likely to tear their anterior cruciate ligament (ACL) than their male counterparts, but the reason behind the phenomenon has yet to be determined. A new study, funded by FIFA, aims to answer that question.
The ACL is a major ligament in the knee that helps stabilize the joint. According to UCHealth, recovery from an ACL injury typically takes nine to 10 months and traditionally involves surgery and rehabilitation.
Over the next year, Kingston University in London will investigate a "possible link" between ACL injuries in women and menstrual cycles.
The FIFA-funded study will conduct blood and physical performance tests on female soccer players, examining the "concentrations of female-specific hormones such as oestrogen and progesterone in the blood, both of which have been linked to increasing ligament laxity and a decrease in neuromuscular reaction times." The blood analysis will then be compared to the physical performance data of the athlete, hoping to determine if there is a correlation between menstrual cycles and the risk of an ACL injury.
- Denver7 reporter Colette Bordelon talks more about the study in the video below
Dr. Kristin Johnson, a postdoctoral research fellow in the College of Health and Human Sciences at Colorado State University (CSU), studies how the nervous system controls muscles. Before coming to Colorado, she spearheaded a study at the University of Iowa, which examined a woman's ability to regulate areas of their central nervous system and the "potential influence" of sex hormones on that ability. That research also considered how female athletes' capacity to control their knees could change during different phases of their menstrual cycle.
"We didn't specifically look at ACL injury, but we looked at knee control at the time of a perturbation or when an unexpected event happens, which is often a condition when ACL injuries happen," said Johnson. "It was a small study, only 21 athletes, but most of them are high-level D1 athletes. And so, I will say that you can't take away injury information just from a single study, and that's really where a lot of the research is lacking in this area, still."
According to Johnson, one theory is that hormones and the menstrual cycle can impact ACL injuries because of the potential to loosen the ligament. Her study, on the other hand, analyzed how hormones can impact the nervous system and, as a result, the ability to control the knee.
"Are hormones impacting our capacity to regulate, control our knee?" Johnson asked in her research.
Johnson said there is currently not enough information to conclude that menstrual cycle phases truly impact the likelihood of an ACL injury.
"It's really exciting just to have somebody with the name, you know, FIFA, that recognition, actually putting up the support to try to answer these questions," Johnson said about the study, which started this month. "Female athlete research, in general, is far behind compared to male athlete research, but it's improving. But there's still a need for this financial support so researchers and athletes and coaches can work together to try to answer these female-specific questions."
The hope, for Johnson, is that more research leads to more answered questions about what is happening within female bodies and how that impacts performance and injury.
A study from 2021 analyzed more than 5,000 different publications related to sports science and medicine. Of those publications, 63% examined males and females, and 31% included males only. Six percent of the publications focused solely on females.
Denver7 spoke with Colorado coaches and athletes who believe more research on the topic is critical, especially if it means girls and women could better protect themselves while playing the sport they love.
"I've spent probably more than 1,000 hours playing soccer in general," 13-year-old Raegan Lupher told Denver7.
The teen, who has dreams of playing D1 soccer one day, has already seen ACL injuries impact players her age.
"It just would put me behind in what I like to do best," Lupher said about the injury.
Vianeey Alvarez, assistant coach with Regis Groff Fusion Girls Varsity Soccer, has seen ACL injuries take out far too many of her players. She described one instance that she will never forget.
"I can still hear it in my head," Alvarez said. "Once she took that hit, it was just an immediate scream, an immediate cry for help... She doesn't remember any of it, but I told her, 'It's like you lost consciousness.'"
Alvarez knows what an injury like that means for her players.
"We can't expect her to come back. Her season's over," said Alvarez.
Karely Bencomo knew she wanted to play soccer from a very young age.
"I would only see guys play, but then I started seeing girls play, and I was like, 'Wow, I could do that too,'" Bencomo recalled. "As soon as I started playing, I just, I loved it already."
Alvarez said Bencomo was one of the strongest players on the field. The two were preparing for a dominant senior year when their plans came to a screeching halt during a club tournament in November 2024.
"My last game — last 10 minutes — I get slide tackled by a girl and my knee, like, I don't know, popped," Bencomo told Denver7. "I was so scared. I was like, screaming, everything. And I'm usually a player that gets up pretty quick."
Bencomo soon learned she tore her ACL and was forced to sit for her entire senior season.
"I just feel like you lose, like, I don't know, so many opportunities," Bencomo said about missing her last year of soccer.
Bencomo told Denver7 she was experiencing her menstrual cycle when she tore her ACL.
"Unfortunately, like, there's not much research, and we're just starting. And it sucks because maybe had Karely known that if she was on her period, she could have maybe taken it a little slower," Alvarez said. "Maybe she would have played her senior year."
Even if Bencomo knew about the research being done, she believes she still would have given her all in that last game. While her future on the field is uncertain, Bencomo is sure soccer will still be in her life in some way.
"I'll play for fun," Bencomo said. "I might coach a little girls' team."
