Twist of fate

Research explores ACL injuries in female athletes

An NCAA study found that women suffered about twice as many noncontact ACL injuries as men in soccer and three times as many in basketball.

By Rick Moore

Published on September 3, 2004

If you've paid much attention to women's sports in recent years--either at the collegiate or prep levels--you've probably noticed a distinct trend... or an epidemic, it can seem at times. Compared to males, female athletes tend to experience far more knee injuries to the anterior cruciate ligament (ACL). (The ACL connects the tibia to the femur in the center of the knee.) A torn ACL--that dreaded snap or pop on the field or the court--is among an athlete's worst nightmares. It can often mean the end of a season, a date for surgery, and a year or more of rehabilitation.

The increased incidence of ACL injuries in female athletes has long been a focus of University researcher Elizabeth Arendt. According to Arendt, the injury disparity came to light with an NCAA study in the early 1990s comparing female and male athletes in soccer and basketball--two sports played among both genders with virtually the same rules and equipment. Women were found to suffer about twice as many noncontact ACL injuries as men in soccer and three times as many in basketball.

"There is no evidence to date that supports a hormonal or anatomical cause, despite a decade of research," says Arendt.

Unfortunately, in the years since that data was collected, little has changed. "We have not budged this data" in the last 10 years, says Arendt.

At the University of Minnesota, the statistics mirror those at the national level. According to Moria Novak, the director of athletic medicine on the Twin Cities campus, ACL injuries for women in three sports--soccer, basketball, and volleyball--have averaged about one per season in the six-plus years she's been at the University.

Why the disparity?

Speculation on the causes for the injury disparity has focused on three potential differences between the genders: hormonal, anatomic, and neuromuscular. Hormonal factors, including the presence of estrogen and menstrual cycle stages, have been studied at great length. While earlier studies suggested that the presence of estrogen might be a factor, Arendt says there is no consensus that sex-specific hormones play a role in increased ACL injuries for females.

As far as anatomy is concerned, women generally have a slightly smaller ACL than men, as well as a smaller intercondylar notch (where the ACL passes through the knee joint). Similar to hormonal differences, Arendt says there is no agreement that anatomic differences account for a higher injury rate in females. "There is no evidence to date that supports a hormonal or anatomical cause, despite a decade of research," she says.

That leaves the broad grab bag of neuromuscular risk factors. These include things like core stability, strength, and proprioception--or inter-muscular coordination--and they're the focus of trainers and coaches at the University.

"We try to teach different functional behaviors, like how you land from a jump," says Novak. "Do you bend your knees and load your weight onto your hips, or do you land with your legs a little straighter, which would put you at higher risk?"

Coaches and trainers also focus on compound exercises that affect multiple muscle groups. "The athletes don't use their muscles in isolation on the field or court," says Sara Wiley, associate director or strength and conditioning for U athletics. "We don't want them to use them in isolation in training."

Arendt points out that the difficulty with intervention strategies is that they take human time and, therefore, money. Young female athletes need to do more than watch videos; they should receive feedback from skilled observers about how they play and move, she says. But an ounce of intervention, in the case of ACL injuries, could be worth a year of rehabilitation. "We do not prevent ACL injuries," Arendt stresses. "We intervene to reduce injury risks."