Did Your Menstrual Cycle Cause Your ACL Tear?

Alexa Simonetti, Geisinger Commonwealth School of Medicine, MBS 2023

Mentor: Dr. Brian Piper, Ph.D.

 A woman’s menstrual cycle has an enormous impact on her life, and this monthly guest is finally getting the recognition she deserves. How periods affect performance has previously been ignored in the athletic community. As a female ex-collegiate athlete, I know this. Thanks to the impacts of social media, the new Internet trend is “cycle syncing” and tailoring your workouts to the phase of your menstrual cycle to correspond with how it impacts your body. For example, it is recommended women perform lower-intensity workouts during their luteal phase, due to them feeling more sluggish, whereas during their follicular phase, they will have more energy to perform with higher intensity. What causes these drastic shifts in energy levels? Hormone fluctuations. Hormones regulate way more than just our energy levels and affect processes such as metabolism, cell growth/death, sleep, and even muscle growth. Due to the much higher prevalence of female athletes sustaining an anterior cruciate ligament (ACL) tear compared to men, it is possible that the hormonal fluctuations during the menstrual cycle could be responsible for this much higher rate of ACL tears.

As a female athlete, my menstrual cycle was never of concern to any athletic trainers or coaches. It was only of concern to me and how it would affect my performance on the field. Unbeknownst to me, there was the possibility this could cause or predispose me to an injury. Current research suggests that certain phases and hormonal events that occur during a female athlete's menstrual cycle could put her at risk of sustaining ACL injury.

There are three phases of the menstrual cycle: follicular, ovulatory, and luteal. These phases are distinguished by their corresponding hormonal fluctuations, with estrogen and progesterone being the ones who run the show. The follicular phase displays a slow rise in estrogen until it spikes at the very end of the follicular phase/beginning of the ovulatory phase, which then causes the release of an egg. During the luteal phase, estrogen levels drop and there is a rise in progesterone.

A normal period has a 28-day cycle, with days 1-14 corresponding to the follicular phase, ovulation occurring on day 14, and days 15-28 belonging to the luteal phase. The estrogen spike that occurs directly before ovulation, has been shown to cause increased ACL laxity and decreased fibroblast and collagen growth with the majority of ACL tears occurring during this phase. Estrogen causes the ACL to become less stable and it increases one’s risk for injury. Oral birth control pills that have a higher progesterone to estrogen ratio have displayed protective effects against ACL tears, meaning athletes taking these kinds of birth control were at a lower risk for sustaining an injury due to it regulating their hormone levels and preventing ovulation.

This research opens the door for a new level of protective protocol to be implemented for female athletes. How can athletic trainers and coaches use this information to protect their athletes? Athletic trainers and coaches should require female athletes to track and report their menstrual cycles to properly monitor injury risk at specific times throughout the month for their players. By using the information on how estrogen affects the ACL, trainers can create preventative programs to strengthen the ACL against the disruptive effects of estrogen and implement enhanced rehab and recovery programs post-practice or game. As most female athletes track their periods, this would be easy data to attain and could help decrease the prevalence of ACL injuries in female athletes.