Major Musculoskeletal Injuries and the Menstrual Cycle: A Case Study




Prado, Cynthia


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Background: There is a clear difference between males and females in the incidence of certain sports injuries. For example, females are about 9 times more likely to experience anterior cruciate ligament (ACL) tears, while males are about 7 times more likely to experience calcaneal (Achilles) tears. These discrepancies warrant further evaluation into the core differences between males and females, one of which is the menstrual cycle. During the first 15 days of the of the menstrual cycle, estrogen levels rise. There is discussion in medical literature about estrogen’s effects on the musculoskeletal system, which may begin to correlate these injury rates and menstruation. One study measured estrogen levels and presynaptic inhibition in males and females during day 1 and day 15 of the menstrual cycle, and found that both measurements were significantly different on day 15. This suggests that as estrogen concentration increases in the first half of the menstrual cycle, gamma-aminobutyric acid (GABA) in the spinal cord is attenuated, decreasing pre-synaptic inhibition, resulting in altered skeletal motor control. Another study evaluated estrogen’s effect on failure load, which is the force necessary to break or tear a certain object. It analyzed two groups of ovariectomized rabbits, administering estrogen supplementation to one and not the other. It found a reduction in failure load in the hormonal substitution group, implying that tendons and ligaments under estrogen’s influence could rupture at a lower applied force. Another study analyzed the extracellular matrix (ECM) enzyme lysyl oxidase (LOX), which oxidizes lysin in collagen and elastin, mediating the cross-linking between these ECM fibrils. It showed that estrogen inhibits LOX activity in engineered ligaments, implying that the increased estrogen in vivo may decrease the stiffness of tendons/ligaments in women, leading to increased risk of injury. This case illustrates two major musculoskeletal injuries in a young female patient that both occurred within the first fifteen days of her menstrual cycle. Case information: 17-year-old female sustained a right ACL tear during a track meet on day 5 of her menstrual cycle. The same female at age 27 sustained a left Achilles tear during a recreational volleyball game on day 6 of her menstrual cycle. In both occurrences, the patient had no previous injury to the area, no medical conditions, and was not taking any medication. Conclusions: The fact that both of this patient’s major musculoskeletal tears occurred during the first week of her menstrual cycle suggests that changing hormones may have influenced these injuries. The studies that support this conclusion have evaluated estrogen’s effects on the musculoskeletal system and concluded that estrogen has been shown to 1) decrease presynaptic inhibition, 2) reduce failure load, and 3) decrease the stiffness of tendons/ligaments. This research together may begin to explain the correlation between this patient’s injuries and her menstrual cycle. More research is needed on this topic, so that we can definitively identify all risk factors for these kinds of injuries and begin to take steps toward prevention for the appropriate athletes.