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The Cycle of Knee Injuries in Women: Hormones and the ACL

Women are eight times more likely than men to injure the anterior cruciate ligament (ACL) of the knee. New research suggests that hormone levels may have something to do with women's ACL injuries. In other words, women may be more prone to ACL injuries during certain times of the month.

Scientists measured hormone levels in 65 women with recent ACL tears. Hormones were measured with urine samples taken within 24 hours of injury and again at the start of the next menstrual cycle. More injuries occurred at the time of ovulation (release of egg) than any other time of the month.

Twenty-four hours before ovulation, there is a sharp increase of  luteinizing hormone in the blood. This hormone triggers the release of estrogen in preparation for reproduction. This lasts about five days. During this time, women are more likely to injure their knees. Interestingly, women taking birth control pills are less prone to knee injury.

Women are more likely to injure the ACL during the ovulation phase of the menstrual cycle. This is especially true for women who are not taking birth control pills. Birth control pills appear to have a protective effect against ACL injuries. The exact reason for this remains unknown.

References: Edward M. Wojitys, MD, et al. The Effect of the Menstrual Cycle on Anterior Cruciate Ligament Injuries in Women as Determined By Hormone Levels. In The American Journal of Sports Medicine. March/April 2002. Vol. 30. No. 2. Pp. 182-188.

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