In addition, male athletes use the muscles that flex the knees more than women do, an action that protects the ACL from injury during landing. Women tend to depend on ligaments to protect their knees after a jump rather than controlling the inward or outward slack with muscles.

Can these injuries be prevented?
In 1993, Frank R. Noyes, MD, and colleagues designed a series of exercises to help athletes refine neuromuscular control of the lower limbs and to increase vertical jump height. The results included a reduction in landing force of 22 percent, 50 percent less side-to-side twisting of the knee joint on impact with the floor, and a 10 percent increase in vertical jump.

"Our research is showing that proper training can decrease knee injuries in females," said Noyes. "Although the increase in knee injuries in female athletes is most likely due to a number of factors, we can see that training may be able to override one or more of these factors," said Noyes. "The program made a female athlete less likely to injure her knee." A report, highlighting the study's significant findings, was presented at the 1998 AOSSM (American Orthopaedic Society for Sports Medicine) annual national meeting and will be published in the American Journal of Sports Medicine. It was selected as the year's number one research project.