Women's Knee-Injury Mystery Unsolved

It's still a mystery why women suffer more knee injuries
than men do. And an elaborate new study fails to link ACL rupture to menstrual
cycle.

The ACL -- the anterior cruciate ligament -- helps keep the knee stable.
When overloaded, the ACL ruptures. This is extremely painful, as sport fans
know from the familiar sight of athletes collapsing in agony. It also takes a
long time to heal.

Female athletes suffer ACL rupture much more often than do male athletes. In
soccer and basketball, women suffer ACL injuries three times more often than
men do. While running obstacle courses during military training, female
recruits suffer 11 times more ACL injuries than do male recruits, note the
researchers.

Why? There's some evidence that ACL injuries are more common during certain
phases of the menstrual cycle, although studies differ as to exactly which
phase is to blame.

To settle the question, Ohio State University researcher Ajit M.W.
Chaudhari, PhD, and colleagues used video tapes to analyze men and women as
they performed various exercises that stressed their knees -- their ACLs in
particular.

The study enrolled 12 men and 25 women. Thirteen of the women were taking
oral contraceptives. Each woman underwent testing at different phases of her
menstrual cycle.

The result: Regardless of their menstrual phase or contraceptive use, women
put no more strain on their ACLs or related muscles than did men.

"Hormone cycling in women does not appear to affect either knee joint or
hip joint loading," Chaudhari and colleagues report. "Women do not
appear to have significantly different loads than men during any phase of the
menstrual cycle. Moreover, the use of an oral contraceptive does not appear to
affect joint loading."

If there is an effect of sex hormones on knee injury, the researchers
suggest, it must be part of a complex interaction between hormones, ligament
structure, fatigue, and "neuromuscular control."

The study appears in the May issue of The American Journal of Sports
Medicine.

By Daniel DeNoon
Reviewed by Louise Chang
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