Age at Menarche Affects ACL Injury Incidence but Not Knee Laxity in Female Athletes.

Abstract

Female athletes sustain anterior cruciate ligament (ACL) injuries at 3-8 times the rate of males playing the same sports, with significant consequences for lifelong health. Our previous work has shown that earlier menarche is related to a higher incidence of ACL injury in association with biomechanical risk factors. Alternatively, earlier menarche may increase injury risk through effects on knee laxity, particularly inter-limb asymmetry in laxity, an ACL injury risk factor that fluctuates with menstrual cycle hormone levels. We hypothesize that, with younger age at menarche, exposure to elevated reproductive hormone levels earlier in development affects knee laxity, thereby increasing ACL injury risk. PURPOSE: To determine relationships between age at menarche, knee laxity, and ACL injury incidence in female college athletes. METHODS: The sample included 121 female student athletes at Wright State University. Age at menarche, current menstrual status, and ACL injury history were obtained in injured and uninjured subjects by self-report questionnaire. Knee laxity was measured in a subset of uninjured subjects (N = 65) to determine injury risk related to age at menarche in healthy knees. Passive anterior displacement and maximum manual displacement were measured with an analog knee arthrometer. RESULTS: Of 121 total subjects, 13 reported having had at least one ACL injury and reconstructive surgery. Mean age at menarche for the full sample was 13.3 ± 1.4 years, and was significantly lower in ACL-injured vs. uninjured subjects (12.7 ± 1.3 vs. 13.4 ± 1.4 years, respectively; P = 0.04). When limited to only those sports played by injured subjects, age at menarche still differed between injured and uninjured subjects (12.7 ± 1.3 vs. 13.6 ± 1.4 years; P = 0.02). Among uninjured subjects, mean values of absolute inter-limb asymmetry were 1.5 ± 1.2 mm for passive anterior displacement and 2.5 ± 1.7 mm for maximum manual displacement. Age at menarche was not correlated with inter-limb asymmetry in either laxity measure (passive anterior displacement: r = 0.17, P = 0.17; maximum manual displacement: r = 0.16, P = 0.19). The results did not change when controlling for current menstrual status. CONCLUSIONS: Earlier menarche is related to higher ACL injury incidence, but not inter-limb knee laxity asymmetry in female college athletes.