The odds of injuring your knee playing sports are higher if you're a woman, reports a new study.
And if you happen to be a woman playing a sport that involves a lot of stopping and turning, your knees may be at even greater risk.
"Women are experiencing an injury rate of two to eight times more than men," says study author Dr. Edward Wojtys, a professor of orthopaedic surgery at the University of Michigan School of Medicine.
But besides confirming that female athletes face a greater risk of knee injury than their male counterparts, they also found that women who play so-called pivot sports - like basketball, netball, volleyball and soccer - are more likely to hurt their knees than either male athletes or other women whose sports don't involve pivoting.
Just why, remains a bit of a mystery. Some scientists suspect hormones may play a role, somehow making women more prone to these particular joint injuries. But Wojtys and his colleagues focused on possible neuromuscular causes.
The researchers measured what they call rotational knee stiffness, which represents the level of protection that the knee muscles can offer. The stiffer these muscles are, they say, the better protected from injury the athlete is.
They recruited 52 college athletes to participate in the study - 24 who played pivot sports and 28 who participated in non-pivot sports like cycling, running and crew.
Athletes who play pivot sports are more likely to suffer injuries because of the fast stops, twisting and turning required of their sports, but the researchers also believed that these athletes would have the highest levels of knee stiffness because of their training.
"People who play jumping sports should be the most protected," Wojtys says.
Each group was split equally between men and women, and the athletes were matched for age, height, weight, activity level, shoe size and body mass index, a measurement that takes into account both height and weight.
The researchers then used a special device designed to measure knee stiffness when muscles were relaxed and contracted while bent at 30-degree and 60-degree angles.
As they'd suspected, when men who played pivot sports contracted their muscles, their knee stiffness increased significantly more than it did in men who played non-pivot sports, the researchers say.
But the same didn't hold true for women.
Both groups of women - those who did and those who did not play pivot sports - had lower levels of knee stiffness than the men, the study shows.
However, the women who played pivot sports had significantly less knee stiffness than the women who didn't play these sports, making them the most susceptible to injury of all the groups.
"Something in their training and conditioning programs is making them more susceptible," Wojtys says of the women who play pivot sports.
Dr. Todd Schlifstein, a clinical instructor of rehabilitation medicine at New York University Medical Centre, says previous studies had suggested that women were more susceptible to knee injuries, but this study really proved the association.
"We may need to treat women athletes differently if they're at higher risk of injury," Schlifstein says, suggesting that specific strengthening exercises may need to be developed for women to prevent these injuries.
What to DoIt's hard to know yet what might need to be changed. Currently, male and female athletes go through the same training and conditioning, but based on the results of this study, something is not working for the women, he says.
In the meantime, he says, female athletes should continue strength training exercises.