ACL tears sideline female athletes

By Marta Lawrence
The NCAA News

Alexia Mickles lunged the wrong way, heard a loud crack and her softball season was over. Mickles, a soccer and softball student-athlete at Penfield High School near Rochester, New York, went to the ground holding her knee.

She had torn her anterior cruciate ligament, or ACL.

Although the research varies, female athletes are two and a half to four times more likely to tear their ACLs than men, depending on the sport. Understanding the reasons behind these disproportionate numbers is “the million dollar question,” says Dr. Michael Maloney, director of the sports medicine division at the University of Rochester Medical Center.

Through a local grant, Maloney is leading an effort to train area female high school athletes, including Mickles, about how to protect their knees from injury.

Athletes who enter the program are provided with a screening to determine how they jump, land, run, cut and pivot. Once the athlete’s at-risk positions have been identified, she is given a series of exercises and conditioning drills designed to retrain her muscles’ response to those activities.

In its first year, the injury prevention program reached almost 1,300 soccer, basketball and volleyball student-athletes in 26 high schools in the Rochester area. During that time, Maloney says there were five non-contact ACL tears, which he says was “a pretty low number.” Maloney typically would expect to see one and a half to two ACL tears per 100 female athletes participating in those sports.

The program wasn’t implemented in time to prevent Mickles’ original injury, but she says she’s happy she has the opportunity to participate now. “I really think it would help if every team were able to do it because I think there would be even less injuries,” she says.

While training programs like the Rochester program have succeeded, they struggle against biological and sometimes social factors – battles that, according to some, boys don’t ever wage.

Unlike male athletes, for example, female athletes tend to land in a knock-kneed position. Most researchers point to this subtle difference as one of the main reasons women are more likely to tear their ACLs than men.

Nerve-firing patterns between the thigh muscle and the hamstrings – called the neuromuscular response – are different in women than in men, says Thomas Trojian, director of the injury prevention and sports outreach programs at the New England Musculoskeletal Institute and team physician at Connecticut. “As women and males reach puberty, they tend to land differently,” he says.

“Boys are running around and athletic and are being trained from a neuromuscular perspective early on and women are later to get into that, and they never develop the same neuromuscular training as boys do even if they’re incredible athletes,” says Dr. Craig Levitz, chairman of the Department of Orthopedics, Orthopedic Surgery and director of sports medicine at South Nassau Communities Hospital in Oceanside, New York.

While Levitz says neuromuscular training programs that teach the muscles how to protect the knee are critical for girls, they don’t seem to be necessary for boys. “For some reason, that’s something that seems ingrained in the male genetics and has to be learned in the female genetics,” he says.

Implementing programs that target young female athletes is key, Trojian says, because, “muscle-firing patters have been set and it’s harder to break as people get older. You’ve been successful – very successful – by doing what you do and now someone is asking you to change what you do, and that’s not that easy.”

Training programs, like those in Rochester, are designed to overcome natural tendencies, which can be difficult. “No one teaches you how to run,” Levitz says. “No one teaches your muscles how to contract when you land or jump. That’s something that just happens– your body just figures it out.”

Without practice and repetition, an individual’s body will do what comes naturally and those natural tendencies can be risky for women. For that reason, participants in the Rochester program are encouraged to incorporate the stretching, strengthening and plyometrics exercises in daily warm-ups and practices. The intent is to make these exercises part of the athlete’s routine, training her body to respond differently.“

Muscle memory is sometimes hard to reverse,” says Maloney, “but certainly it can be done.”

Some researchers also cite hormones in explaining a female’s vulnerability to ACL tears. As women mature, their bodies produce chemicals such as estrogen, which make their joints more flexible and therefore more prone to tears. As men mature, their bodies produce more muscle, which can protect the knee.

“Estrogen affects the collagen production and there appear to be times in the menstrual cycle when people tend to be able to identify greater ACL tears,” says Trojian. He cautions, however, that the findings vary and without hormonal studies across a large female athlete population, a link between hormones and ACL tears cannot be definitively proven. If hormones do play a role, Trojian thinks the impact is likely small.

Anatomical differences

Women and men also have important difference in the anatomy of their knees. For example, female ACLs are smaller than male ACLs.

The notch housing the ACL is also typically smaller in women than in men. “Most people have noticed that women that tear their ACL have a much tighter notch,” says Levitz. The smaller notch leaves less room for movement when a person hyperextends.

Most experts agree, even with programs like those in Rochester, women will continue to be at a greater risk for ACL tears than men. “I don’t know if it’s a researchable answer,” says Levitz, “It’s not like cancer. In my opinion there’s not a cure. It’s just one of the occupational hazards of female athletes.”

Nobody may be able to explain why women are more prone to ACL injuries than men, but for athletes like Mickles, training muscles to respond differently may be the best chance at preventing future injuries.