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Abstract & Commentary
Synopsis: Wojtys and colleagues found that most injuries occurred in the ovulatory phase of the cycle (day 10-14). The association between the athletes’ menstrual cycle phase and the likelihood of injury was statistically significant (P = 0.03).
Source: Wojtys EM, et al. Association between the menstrual cycle and anterior cruciate ligament injuries in female athletes. Am J Sports Med 1998;26(5):614-619.
Identifying the risk factors for the increased rate of anterior cruciate ligament (ACL) injuries in women athletes has been a recent priority among sports investigators. This study by Wojtys and colleagues highlights one area of intense investigation—the influence of estrogen levels or, more specifically, the stage of the menstrual cycle on ACL injury rates. This group of combined investigators from the University of Michigan Hospitals in Ann Arbor and the Cincinnati Sports Medicine and Orthopaedic Center retrospectively surveyed 28 young athletes (23 ± 11 years) with regular periods who sustained a noncontact ACL injury. They found most injuries occurred in the ovulatory phase of the cycle (day 10-14). The association between the athletes’ menstrual cycle phase and the likelihood of injury was statistically significant (P = 0.03). Estrogen peaks at mid-cycle just prior to ovulation, raising the question as to whether peak estrogen levels may increase one’s susceptibility to a non-contact ACL injury. Wojtys et al are quick to admit that, to date, the clinical and practical significance of such an association is unknown.
Comment by Letha Y. Griffin, MD, PhD
Noncontact ACL injuries are being seen at an alarming high rate in women athletes (4-8 times greater than in men)—especially those performing pivotal sports such as basketball and soccer.
Proposed risk factors include women’s increased joint laxity, their narrower femoral notches, and their smaller ligament size. Women’s decreased total muscle mass, their decreased hamstring-to-quadriceps ratio, and proposed less favorable neuromuscular control have also been blamed. Others feel women’s body mechanics, influenced by such factors as their lower center of gravity and increased knee valgus, hip varus, and foot pronation, is a predisposing factor and results in more "out of control" play.
Since increased estrogen levels are unique for women and since estrogen is known to have a direct effect on collagen metabolism, investigators questioned whether there could be a relationship between estrogen levels and ligament injury. Research efforts along these lines intensified after Liu and associates1 and Sciore and colleagues2 reported finding estrogen and progesterone receptor sites in human anterior cruciate ligaments.
This article by Wojtys et al adds another piece to the estrogen puzzle. Although their data are enticing, they remind us of their study’s limitations, which most noticeably include the lack of actual measured estrogen levels, the wide age range of participants (11-42 years), and the fact that all data on the stages of the menstrual cycle at the time of injury were retrospectively gathered from patient recall rather than accurately recorded at the time of the injury. This study is also contrary to the proposal of Thomas and associates3 that the greatest incidence of ACL injury is most likely to be during the premenstrual phase of the menstrual cycle when normal knee laxity is greatest. Now, there seem to be more questions than answers regarding risk factors in ACL injury, but early data on estrogen’s influence is intriguing.
1. Lui SH, et al. Primary immunolocalization of estrogen and progesterone target cells in the human anterior cruciate ligament. J Orthop Res 1996;14:526-533.
2. Saciore P, et al. Detection of receptors for estrogen and progesterone in human ligaments and rabbit ligaments and tendons by RT-PCR [abstract]. Orthop Trans 1997;21:736.
3. Thomas R, et al. The influence of the menstrual cycle on ACL laxity. Oral presentation at AOSSM Annual Meeting, New Orleans, LA, March 22, 1998.