Women's knee risk higher, but only in some sports

NEW YORK (Reuters Health) - Women have been shown to suffer knee ligament tears more often than men. But a new study hints that this may be true only in a limited number of physical activities.

Numerous studies have found that female athletes are more likely than their male counterparts to rupture the anterior cruciate ligament (ACL), a tough band of tissue that connects the thigh and shin bones and stabilizes the knee joint.

ACL injuries are often the result of a sudden, forceful twist, so the injury is fairly common in sports that involve quick stops and starts, pivoting and jumping -- such as basketball, soccer and volleyball.

In the new study, which followed West Point cadets over 10 years, researchers found that when they considered physical activities as a whole -- including intercollegiate team sports, club activities and gym class -- young men and women sustained ACL tears at a similar rate.

However, certain activities seemed to put female cadets at particular risk. In gymnastics class -- a required course at West Point -- females suffered ACL tears at nearly six times the rate of their male counterparts. Similarly, female basketball players had an injury rate between two and three times that of male players.

Female cadets were also more likely to injure their ACL during required obstacle-course tests.

Beyond this, however, there were no clear gender differences in other sports and activities, the researchers report in the American Journal of Sports Medicine this month.

Dr. Sally B. Mountcastle, of the Keller Army Community Hospital at West Point, led the study.

The findings are based on 10,419 students who graduated from West Point between 1994 and 2003; during that time, Mountcastle's team documented 353 ACL injuries.

It's interesting, according to the researchers, that gymnastics class and obstacle-course tests seemed to put women's knees at greater risk.

The gymnastics course, they note, includes many of the things that are thought to help prevent ACL injuries -- such as learning proper jumping and landing techniques, and exercises to increase strength and agility. The class also teaches cadets how to go through the obstacle course properly.

So it's likely that factors other than training -- whether biological or environmental -- explain women's higher rate of ACL tears in these activities, according to the study authors.

Experts have a number of theories on why women have a higher rate of ACL injuries, at least in certain sports. Anatomical and muscular differences between men and women may play a role, and there is some evidence that women's ACL risk is higher at certain points in the menstrual cycle.

SOURCE: American Journal of Sports Medicine, October 2007.