knee injury
ACL tears are far too common in athletes. (For Spectrum Health Beat)

Women are more likely than men to suffer a knee injury called an anterior cruciate ligament (ACL) tear. But—surprisingly—the injury occurs the same way in both genders, a new study reveals.

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Our Take

Through his experience as a team physician for the MLB, NBA, NFL, NASA, and a variety of high schools and universities, Kendall Hamilton, MD, agrees wholeheartedly about the primary cause of ACL injuries.

“Patients often describe feeling as if the knee hyperextended when they were trying to slow down and change direction during competition,” Dr. Hamilton said. “They often feel a pop in the knee, which is immediately followed by swelling and pain. After a few days the pain subsides and the knee feels stiff and unstable.”

As a Spectrum Health Medical Group orthopedic surgeon who specializes in sports medicine and arthroscopic surgery, Dr. Hamilton performs about 120 ACL reconstructions a year.

Most research, he noted, shows that the higher incidence of ACL tears seen in females is attributed to hormonal changes, neuromuscular development, knee alignment angles and jump-landing techniques.

“These factors often lead to more force and strain across the ACL during times of competition that leads to more ACL tears in the female population,” Dr. Hamilton said. “ACL prevention programs aimed at targeting neuromuscular development, knee alignment angles, and jumping-landing mechanics have shown a lot of promise in reducing the incidence of ACL tears.”

He and the Spectrum Health Medical Group Sports Medicine team have piloted such ACL prevention programs to serve local high schools and universities.

Prior research suggested women are two to four times more likely to suffer ACL tears due to differences in how this type of injury occurs in the sexes, researchers at Duke University, in Durham, N.C., noted.

But that theory is wrong, according to the results of a new study of 15 women and 15 men with torn ACLs. Those prior studies were based on slow-motion replays of injuries, while the new work relied on scans and other advanced techniques.

“Based on watching videos of athlete injuries, previous researchers have suggested that females may have a different mechanism of injury than males. But it’s difficult to determine the precise position of the knee and the time of injury through footage,” said study leader and biomedical engineer Louis DeFrate.

In order to develop improved treatment strategies and prevention, we need a clear understanding of what motions are most dangerous for athletes.

Researcher Louis DeFrate

“We used MRI scans taken within a month of the ACL rupture and identified bruises on the surface of the two large bones that collide when the ACL tears—the femur and the tibia—then used 3-D modeling and computer algorithms to reconstruct the position of the knee when the injury occurred,” he explained in a Duke news release.

“Our results suggest that males and females have the same position of injury,” DeFrate said.

The study was published online in the American Journal of Sports Medicine.

It was long believed that ACL tears were caused by an inward buckling of the knee. However, a previous study by DeFrate and colleagues concluded that landing on a hyperextended knee—when the knee is bent backwards—is what causes an ACL tear.

“In order to develop improved treatment strategies and prevention, we need a clear understanding of what motions are most dangerous for athletes,” DeFrate said.

According to DeFrate, this work provides new evidence that landing on an extended knee may be a dangerous position for ACL tears in both sexes.