Risk of Knee Ligament Injury Tied to Ovulation


Updated: Wed, Aug 22 10:48 AM EDT
NEW YORK (Reuters Health) - Women are known to face a greater risk of knee ligament injury compared with men. Now new study findings suggest that ovulation, and possibly oral contraceptive use, may play important roles in women's odds of injuring their anterior cruciate ligaments (ACL).
The investigators found that women were nearly three times more likely to sustain an ACL injury while they were ovulating than during other points of the menstrual cycle. But because this pattern emerged only among women not on birth control pills, the findings also suggest oral contraception may provide some measure of protection from the injury, the researchers note.
However, lead study author Dr. Edward M. Wojtys stressed that the findings do not suggest birth control pills offer a way to prevent ACL injuries.
"This research does not justify pulling young ladies out of sports or putting young women on oral contraceptives in order to prevent ligament injuries," Wojtys, the director of sports medicine at the University of Michigan in Ann Arbor, said in a statement.
"There is some evidence that ACL injuries are tied to the menstrual cycle and probably to hormones," he added, "but we don't have enough information yet to justify the use of oral contraceptives in order to prevent ligament injuries."
Wojtys and his colleagues studied 65 women with ACL injuries, collecting urine samples within a day of each woman's injury to establish the phase of her menstrual cycle. They found that more than 2.5 times the expected number of injuries occurred during mid-cycle, or ovulation.
Wojtys presented the findings at a recent meeting of the American Orthopaedic Society for Sports Medicine in Keystone, Colorado.
Studies indicate that female athletes rupture their ACLs up to eight times more often than male athletes do. The ACL is a tough band of tissue that helps stabilize the knee, and ACL tears occur most commonly in sports that require quick pivoting and jumps, such as basketball and soccer.
A number of factors--from differences in musculature and training methods to women's wider hips--are believed to account for the higher rate of ACL injuries among females. Previous research has also pointed to the role of the menstrual cycle, showing that ACL injuries are more common during ovulation. Estrogen levels are increased during ovulation, and since ligaments have estrogen receptors, some researchers have speculated that hormone fluctuations factor into women's ACL injury risk.
But Wojtys said this relationship remains unproven. "Even if it is the menstrual cycle that is having some effect on the susceptibility of soft tissue...the susceptibility is not clear," he said in the statement.
"People are jumping to the conclusion that it is estrogen and it is acting at the anterior cruciate ligament, when in fact, there are multiple places where any hormone could act, including muscles, the central nervous system and the peripheral nervous system," Wojtys added.
He called for further research into how hormones affect ligaments and other soft tissue, as well as how they might alter the function of muscles and nerves.

Also:

Am J Sports Med 1998 Sep-Oct;26(5):614-9

Association between the menstrual cycle and anterior cruciate ligament injuries in female athletes.

Wojtys EM, Huston LJ, Lindenfeld TN, Hewett TE, Greenfield ML.

MedSport, Section of Orthopaedic Surgery, University of Michigan, Ann Arbor, USA.

Anterior cruciate ligament injury rates are four to eight times higher in women than in men. Because of estrogen's direct effect on collagen metabolism and behavior and because neuromuscular performance varies during the menstrual cycle, it is logical to question the menstrual cycle's effect on knee injury rates. Of 40 consecutive female athletes with acute anterior cruciate ligament injuries (less than 3 months), 28 (average age, 23 +/- 11 years) met the study criteria of regular menstrual periods and noncontact injury. Details concerning mechanism of injury, menstrual cycle, contraceptive use, and previous injury history were collected. A chi-square test was used to compute observed and expected frequencies of anterior cruciate ligament injury based on three different phases of the menstrual cycle: follicular (days 1 to 9), ovulatory (days 10 to 14), and luteal (day 15 to end of cycle). A significant statistical association was found between the stage of the menstrual cycle and the likelihood for an anterior cruciate ligament injury (P = 0.03). In particular, there were more injuries than expected in the ovulatory phase of the cycle. In contrast, significantly fewer injuries occurred in the follicular phase. These hormones may be a factor in the knee ligament injury dilemma in women.

 

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*       Am J Sports Med. 1999 Mar-Apr;27(2):270-1

*       Am J Sports Med. 2000 Jan-Feb;28(1):131