Among the most dreaded injuries in sports, the rate of anterior cruciate ligament (ACL) injuries among high school athletes has grown significantly over the past 15 years, according to a new data analysis by organizations collaborating to assess and address the problem of serious knee injuries.
The National ACL Injury Coalition reviewed injury data for 12 major girls and boys sports over five three-year periods from 2007 to 2022, as supplied by certified athletic trainers in the High School RIO surveillance program. From period one to five, the average annual ACL injury rate grew 25.9% to 7.3 injuries per 100,000 athlete exposures. ACL injuries now represent more than 14% of all injuries involving the knee.
The analysis offers a major update of national ACL injury figures for high school sports participants. Drawing on medical reporting from more than 100 U.S. public high schools, it is the first study since 2013 to explore the prevalence of the injury in high school sports. The analysis captured annual athletic trainer-reported knee injuries, regardless of the participant’s age or level of play in the school, and then created average annual rates for each three-year period. A 12% increase in annual ACL injury rates was also found when comparing strictly by individual year, as highlighted in the State of Play 2023 Report.
“The negative health impacts of ACL injuries are significant, both in the short-term and the long-term,” said Dr. Joseph Janosky, lead researcher for the coalition’s analysis and director of athlete health at Hospital for Special Surgery (HSS), a founding partner of the coalition.
“Among the most concerning long-term health issues is the development of osteoarthritis after ACL injury. It's important for high school athletes and their parents and coaches to understand that the health issues related to ACL injury can last a lifetime.”
The analysis also confirms that girls and participants in cutting and landing sports injure the ligament most often. Rates of injury in girls sports grew 32.3%, compared to 14.5% for boys sports. Among girls sports, soccer experienced the highest average annual rate (13.3 per 100,000 exposures), followed by basketball (12.2) and lacrosse (10.4). Importantly, rates for girls volleyball (3.2) and lacrosse grew more than any sport/gender over the period studied, a staggering 96.7% and 83%, respectively.
For girls lacrosse, the combination of a high annual incidence rate and dramatic participation growth places the sport on par with soccer and basketball as the three most at-risk girls sports.
Among boys sports, football ranked first in annual rate (12.6) while boys lacrosse (7.8) experienced a major jump, rising 61.5%. Soccer ranked third among boys sports and grew 13.7%.
“High school sports play an important role in the adoption and maintenance of a physically active lifestyle among millions of U.S. adolescents,” said Dr. Christy Collins, president of the Datalys Center for Sports Injury Research and Prevention, a nonprofit research organization that administers the High School RIO program. “Too often, injury prevention in this population is overlooked as sports-related injuries are thought to be unavoidable. In reality, sports-related injuries are largely preventable through evidence-based interventions.”
Differences in non-contact ACL injuries
Evidence of rising injury rates for high school athletes comes at a time of growing public awareness and concern, particularly for girls and women. The injury kept many top soccer players from competing in the 2023 FIFA Women’s World Cup, and across sports, an all-too-common scene is an athlete planting or landing awkwardly in play and then falling to the ground in despair.
The coalition’s analysis offers a key insight: high school girls were significantly more likely to injure their ACL in non-contact fashion, meaning without making physical contact with a teammate or opponent. Of all ACL injuries in girls sports, 57.5% were non-contact, compared to 39.7% in boys sports. The rate was most extreme in girls lacrosse, where more than 8 in 10 injuries were non-contact (82.5%). Research has shown that the most common situations for non-contact ACL injuries involve pivoting or rotating around the knee, such as when defending an opponent or landing from a jump.
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ACL injury is complex, with many contributing factors. However, Janosky highlights the strong connection between non-contact ACL injury and widespread but improvable deficits in lower body control. “Researchers have described many different factors that contribute to ACL injury, but only some of these can be changed or modified to help reduce the risk of injury,” he said. “Currently, inadequate neuromuscular control is one of the most prevalent modifiable ACL injury risk factors among adolescents.”
Janosky and his team at HSS study injury risk factors in youth sports participants and have found that the vast majority of school-age youth, especially girls, struggle to control their knee during tests of basic sport movements. “At least 80% of adolescent sports participants cannot adequately control their trunk or knee joints when performing activities like squats and jumps – key movements for most sports participants,” he said. “While we don't have pre-pandemic data for these deficiencies, I suspect that higher rates of sedentary activity during the pandemic may be contributing to the alarmingly high prevalence of inadequate neuromuscular control.”
The coalition’s analysis found a spike in the annual ACL injury rate during the pandemic period. For the 2020-21 school year, the annual rate of all ACL injuries jumped to 9.3 injuries per 100,000 athlete exposures, the highest single year for the period examined.
Poor lower body control may also contribute to the severity of ACL injuries. While the vast majority of all ACL injuries are complete tears (74.3%), girls suffered complete tears 80.5% of the time, compared to only 68.1% for boys. An overwhelming 90.5% of girls lacrosse players and 82.3% of girls soccer players suffered complete tears. Complete tears also occur at high rates for some boys sports, as just under 80% of both lacrosse and basketball players suffered complete tears.
Key to prevention: neuromuscular training
Despite the injury’s growth, experts remain confident in ways to help young athletes.
Created by the Aspen Institute and HSS, the National ACL Injury Coalition formed in March as a multiyear effort to reduce injury rates in high school sports participants. The coalition’s members agree that rates of non-contact ACL injuries can be reduced through targeted exercises that improve lower body strength and control. Experts call this activity neuromuscular training, which has been associated with fewer ACL injuries, improved athleticism and greater team performance.
“Injury rates among high school athletes should be reduced to the lowest possible level without discouraging youth from engaging in this important form of physical activity,” said Collins, a founding member of the coalition. “This goal can be best accomplished by monitoring injury rates and patterns of injury over time, investigating the cause of injuries, then developing, implementing, and evaluating evidence-based solutions, particularly neuromuscular training.”
A key strategy of the coalition is increasing neuromuscular training in schools, clubs and programs that offer cutting and landing sports. The coalition is developing a toolkit for athletic directors, club leaders, coaches and staff to implement this proven solution. It will include RIIP Reps, an app that uses self-paced, seven-minute sessions that can be completed in the space of a yoga mat and requires no equipment.
The coalition will continue to bolster research and improve public awareness, while working with key sport and school sector leaders to develop policies, incentives and messaging that improve their sector’s understanding of the injury, increase completion of injury prevention courses, and expand proven solutions that reduce risk, such as neuromuscular training.
Health equity will be a priority, promoting injury prevention for underserved youth. ACL injuries often require expensive surgery and rehabilitation that can bring significant financial burden, with injured youth from low-income families experiencing more delays in time to care. Coalition leaders are exploring ways to engage insurance companies, target the toolkit to urban and rural communities, increase access to athletic training services and strengthen medical reporting.
“The coalition needs the high school sports community to rise up and meet this challenge with us,” Janosky said. “We need athletic directors, coaches, parents, athletic trainers and the leaders of regional and state athletic associations to commit to safeguarding the health of athletes. If we work together to bridge the gap between research and the real world, the millions of children who play sports will benefit tremendously.”
Vincent Minjares, Ph.D., is Program Manager with the Aspen Institute’s Sports & Society Program. He leads the program’s work on coaching and school sports and facilitates the National ACL Injury Coalition. He can be reached at vincent.minjares@aspeninstitute.org and followed @PlayerLearning.