Researchers say that women are nearly four times more likely to suffer from a tear to the ACL (anterior cruciate ligament) in the knee than men, but that it may be prevented by a different "landing strategy."
The study, published in the Journal of Athletic Training, was conducted by researchers from Oregon State University (OSU), and University of North Carolina at Chapel Hill and Greenboro.
ACL injuries are defined as a tearing of the anterior cruciate ligament inside the knee joint. The injury causes the knee to swell, and the joint becomes too painful to bear weight.
These injuries are very common in sports where the participants are required to do many "jump stops and cuts." This includes basketball, soccer, tennis and volleyball.
Marc Norcross, assistant professor of exercise and sport science at the College of Public Health and Human Sciences at OSU, says:
This picture shows a Biomechanical model of a female using a "knock-kneed" technique, experiencing high frontal plane knee loading during a jump landing.
"We know that people who hurt themselves tend to look stiff when they land and that the combined 'knee loading' from multiple directions is likely causing the injury event, but it wasn't clear initially why women had more injuries than men."
Women more 'knock-kneed' than men
For their research, the study authors analyzed 82 physically healthy men and women using motion analysis software, to determine exactly how they landed when carrying out a series of jumping exercises.
The researchers found that both men and women landed "stiffly," which can potentially lead to ACL injuries.
However, women were 3.6 times more likely to land in a "knock kneed" position. The researchers say this could be a critical factor causing gender disparity in ACL injuries.
Prof. Norcross says:
"We found that both men and women seem to be using their quad region the same, so that couldn't explain why females are more at risk."
"Using motion analysis, we were able to pinpoint that this inability to control the frontal-plane knee loading - basically stress on the knee from landing in a knock-kneed position - is a factor more common in women.
Future research may isolate why women tend to land this way, but it could in part be because of basic biology. Women have wider hips, making it more likely that their knees come together after jumping."
Norcross says ongoing research will focus on high school athletes in order to determine how ACL injuries can be prevented through warm-up techniques and improved landing strategies.
"We are trying to create a prevention strategy that is sustainable and will be widely used by high school coaches," he adds.
"A lot of athletes do come back from an ACL injury, but it is a long road. And the real worry is that it leads to early onset arthritis, which then impacts their ability to stay physically active."