Monday, July 16, 2001 (HealthDayNews) -- Women who want to avoid a common knee injury should take extra precautions when playing sports during ovulation.
A woman's risk of tearing her anterior cruciate ligament (ACL) is up to three times greater during ovulation than at other times of the month, reports Dr. Edward M.Wojtys, director of sports medicine at the University of Michigan in Ann Arbor.That's the latest addition to a growing body of evidence that suggests reproductive hormonal activity may increase the risk of injuring the ACL, one of the most common sports injuries in women.
"Women are up to eight times more likely to sustain this knee injury than men -- and now there is mounting evidence that hormonal activity, particularly the increase in estrogen seen during mid-cycle, may play a role in increasing the risk of this injury," Wojtys says.
He was the lead author on the study, which was presented at the recent annual meeting of the American Orthopaedic Society for Sports Medicine in Keystone, Colo.
ACL is one of four stabilizing ligaments in the knee. Injury can occur because of a blow to the knee or from a twisting motion of the leg, things associated with sports like tennis, basketball, soccer or even football.
Although research shows estrogen receptors are at the site of the ACL, Wojtys doesn't believe the effects of ovulation are felt directly on the knee itself.
"If you know anything about the physiology of ligaments, it's a little hard to believe that a woman's ACL could go from strong to weak and back to strong again within a few days," he says.
Rather, he explains, the effect of the hormones may be on a neuromuscular level, affecting a woman's coordination and balance, as well as the overall response of her muscles and tendons.
Experts familiar with the research acknowledge the role hormones may play, but also believe these injuries are not limited to single factor.
"There are a variety of intrinsic factors involved here -- hormonal, anatomic, muscle factors -- plus we can't forget training differences in men and women, with women generally taking up sports at a later age than men," says Dr. Elliott Hershman, executive associate director of orthopaedic surgery at Lenox Hill Hospital in New York City.
Because ACL injuries occur throughout a woman's cycle, says Hershman, "hormones are not the whole answer, but likely only part of the answer."
The study itself involved 65 women between the ages of 18 and 38. All began the study within 24 hours of sustaining an ACL injury. It included confirmation of their ovulation cycle via urine samples, which measured hormone markers at the time of injury. This was, in fact, the first study ever to document the exact phase of the menstrual cycle directly following injury, and the first to show a precise correlation to ovulation.
The end result: there were almost three times the number of women ovulating during their injury, compared with those in other stages of their menstrual cycle.
A statistically less significant, but still interesting, finding was that birth control pills may one day prove to have a protective effect on the knees. Of the 65 women, 14 were using oral contraceptives, and their injury rate was analyzed separately. The surprising result: the rate of mid-cycle ACL injury was significantly lower.
"Right now, the number of women in this group is so statistically small that we cannot even make a prediction if, in fact, birth control pills can offer protection from knee injury," says Wojtys. Still, the finding is so intriguing his group is going forward with a second study designed to look at the rate of ACL injury in women on oral contraceptives.
Because birth control pills prevent ovulation, women taking them generally do not experience the same fluctuations in hormones normally experienced with a menstrual cycle. And that, say experts, could make the difference in the rate of injury.
"It's interesting and a very useful finding -- and potentially it could be very helpful and very useful in the right setting," says Hershman.
What To Do
Experts caution that the best way for women to avoid any sports injury, but particularly ACL injury, is to adequately train beforehand.
You can also help offset the risk of injury by doing enough warm-ups before sports and using extra support apparatus when playing during mid-cycle, particularly if you know your knees or ankles are weak spots.
For more information on ACL injuries in women, visit the Hughston Sports Medicine Foundation.
To learn more about sports injuries in women, go here.