Key Points:

  • Females are 8 times more likely to injure their ACL than their male counterparts
  • Firing rates of nerves that control muscle activity were much higher in the week before a woman’s next period than earlier in the menstrual cycle
  • Hormones oestrogen, progesterone, and relaxin rare known to play a role in muscle tone and joint laxity
  • The use of the oral contraceptive pill may reduced the risk of some ACL injuries but the is a paucity of valid evidence

Is your cycle a pain in the knee? Most women will admit that having a monthly cycle is a pain in the neck – it affects your mood, your energy, your ability to want to socialise – just to name a few. But did you know that the hormonal changes surrounding your menstrual cycle also affect the function of the ligaments around the body?

Most of us are familiar with lower back pain or pelvic pain associated with a cycle, but there has also been an increase in the number of reported incidences of knee pain during this time too. Studies show that females are 8 times more likely to injure their ACL than their male counterparts. Further research into this has revealed that menstrual cycle-related changes in nerves that control muscle activity could explain why.

A study into the incidence of ACL injuries in female soccer players found that the firing rates of nerves that control muscle activity were much higher in the week before a woman’s next period than earlier in the menstrual cycle. This difference in firing rates could affect the stability of the knee joint and possibly make it more susceptible to injury in this week. 

In addition to being more susceptible to injury, ligaments have also been shown to undergo a decrease in proprioceptive properties during certain times in the menstrual cycle. This change in proprioception might not be directly linked to specific hormone levels, but to accessory phenomenon such as associated fluid retention, affecting sensory feedback from the mechanoreceptors in the muscle. Regardless of the mechanism, anecdotal evidence suggests that the ability to control your body’s position in space may become compromised during certain phases of your menstrual cycle. 

The hormones involved in the cycle – oestrogen, progesterone, and relaxin, among others – are known to play a role in muscle tone and joint laxity. Exactly what role these hormones might play and what the implications are for injury avoidance remains controversial and further study is certainly underway. 

So what can we do about this risk factor? A recent study into hormones and injury risk hypothesised that the use of the oral contraceptive pill may reduced the risk of some ACL injuries but the is a paucity of valid evidence. Of the 7 studies into the use of oral contraceptives and soft tissue injuries, 2 indicated a high quality of evidence score that showed a decrease in the laxity of the ACL during peak times of the menstrual cycle. Most recent studies seem to have reached contradictory conclusions thus leaving unclear the influence of contraception on the risk of soft tissue injury but certainly an area for further investigation.

So for now we know that women are more susceptible to knee injuries and that cyclical patterns may have an impact on times of the month in which these injuries occur. So next time you feel a bit wobbly on your feet or a bit clumsy, have a think about what phase of your cycle you are in and if needs be, adapt your training to suit your bodies ability.

If you would like more information on how to monitor your training around your menstrual cycle, feel free to send me an email or book an appointment online. We are here to help!

Catherine Allison

Osteopath

catherine@torquaysmc.com.au