Women’s Sport & ACLs – What Makes Women More Likely to Sustain an ACL Injury?

Leanne Simmons

January 16, 2024

Unfortunately, it is becoming more and more common to hear reports of female athletes rupturing their ACL – with our Matilda’s captain Sam Kerr one of the latest victims, but why is there such a high rate of occurrence amongst female athletes? Our physio Leanne has summarised the latest research and data below.

ACL reconstruction | healthdirect
ACL Tear

What is the ACL and what are the stats saying?

The anterior cruciate ligament – most commonly known as the ACL, is a ligament in the knee which prevents forward movement of the tibia and is normally compromised through large valgus and rotation forces. These movements can be replicated through activities such as jumping, landing and cutting. Since the growth of women’s sport, there has been greater emphasis on understanding the reasons why women are more likely to suffer an ACL rupture.

Statistically, Women are 3-6 times more likely to sustain an ACL injury and are 1.7 times less likely to return to pre-injury level of sport in comparison to their male counterparts.

The aim of this blog is to discuss the evidence behind these statistics.

Caitlin Foord, Nicole Beck, Chloe Esposito, Gretel Tippett and Daisy Pearce
AAP/AP

We’re Built Different – the Anatomical Differences

Worst injury fears confirmed for Melbourne Demons forward Ainslie Kemp
GETTY IMAGES

The shape and size of the ACL is determined by the size of the femoral notch, which is where the ACL is housed, and in women, it is generally smaller. It remains unclear however, whether the size of the notch is associated with increased injury risk. The distal (or bottom) attachment, a groove known as the intercondylar notch has been investigated in cadavers and it has been found that women have a narrower notch and therefore smaller ACLs. With these findings, researchers have theorised that a smaller ACL increases the risk of injury, however, when the notch is examined under MRI in live subjects there has been no relationship found between the two.  

An increased laxity in the connective tissue, most commonly known as Hypermobility, is more common in women than it is in men. This laxity theoretically increases the risk of the knee being compromised in ‘extreme’ positions. In fact, the incidence of people attending surgeons for potential ACL reconstructions is higher for those with hypermobility. Despite this, there has been no significant relationship found between hypermobility and the risk of ACL injury, but it is important to recognise that the presentation of hypermobility is different between individuals, and therefore should be considered as a risk factor for ACL injury in women. Improving neuromuscular control around lax joints has been found to reduce the risk of lower limb injury.

The ability to contract and generate torque in the quadriceps and hamstrings muscles has found to be significantly less in women compared to men. These muscle groups act as a ‘protector’ against knee injury. The risk of re-rupture is said to be reduced if the non-dominant leg has more than 70% hamstring strength compared to the dominant leg. Engaging in prevention programmes can reduce lower limb injuries by up to 16% in men.  The data is less clear in women. 

The Q-Angle: Female v Male

The Q angle is defined as the angle between the quadriceps and the patella tendon. This angle determines the force generated by the quadriceps. Associated with negatively altering the biomechanical load of the patellofemoral joint, the greater the angle, the more prone the individual is at risk of injury as the knee sits in more valgus. Women are found to have greater Q angles compared to men. Despite this, the latest longitudinal study opposed the idea of the Q angle increasing risk of ACL injury, where female handball and football players were studied over a five year period. The study found no relationship between pelvic position and Q angle when completing a single leg squat and a vertical drop jump.

We Function Differently – the Hormonal Differences

Hormone Imbalance, Menstrual Cycles & Hormone Testing
Female Hormone Cycle

Hormones such as oestrogen, progesterone and relaxin have cyclical effects with menstruation. Some research suggests that before and after menstruation the ACL becomes weaker and increases the risk of injury. However, controlling hormones through the oral contraceptive pill has had conflicting results, with the most recent study revealing that there is no correlation between the two variables. We must however, consider physical activity levels, where the environment is key in understanding the risk of sustaining an ACL injury.

There are Different Expectations – the environmental and social differences

Recent literature suggests the lack of exposure to training and sport as a potential reason for higher numbers of ACL tears in women; largely influenced by societal and institutional gender norms. Women are less likely to engage in strength programs, less surgeons offer women reconstructions and timelines to return to play are different compared to men. Non standardised injury prevention programs such as the FIFA 11+ have been found to reduce lower limb injury risk throughout the sporting season. Often sex differences are not reported in the evidence, however, the majority of participants are often male, making it unclear whether both men and women can equally benefit.

So what does all this mean?

Questions remain as to whether we should solely blame biomechanical differences on the ACL incidence in women. As the engagement of sport in women increases, the demand for robust research studying these groups is also needed. The literature being based largely on the male athlete before the year 2000, is a clear example of this. Biomechanical differences should not be ignored but considered in a biopsychosocial approach to the injury prevention, rehabilitation and surgery of the ACL in the female athlete. 

With the increased participation of young female athletes in cutting and change of direction sports such as soccer and AFLW, preventative individualised programs consisting of neuromuscular control and strengthening may be highly beneficial. At Grand Slam Physio we can assist with individualised programs and treatment following ACL injuries. To book an appointment book online at our Geelong or Torquay clinics or call 0352772151.

About Leanne

Leanne is a physiotherapist from London, England passionate about all things lower limb rehabilitation. Leanne has gained a lot of her experience in the NHS and in the private sector, working with Sports Physiotherapists and Sports Physicians. Leanne has a interest in lower limb rehabilitation, implementing both manual techniques and exercise prescription. She has completed courses in acupuncture and has also completed an imaging course at Hertfordshire University. She worked as a physiotherapist at the Commonwealth Games, assisting with the athletics team. Leanne has been working with us at our Belmont Clinic prior to her return to England at the end of Jan 2024.

REFERENCES:

  • Akhtar M.A. (2020) Hypermobility, ACL reconstruction & Shoulder instability: A clinical, mechanical and histological analysis (Thesis) NHS File 
  • Devana M. et al. (2022) Disparities in ACL Reconstruction: the Influence of Gender and Race on Incidence, Treatment, and Outcomes, Current Review in Musculoskeletal Medicine, Vol 15 (1)
  • Gould, S., Hooper J., Strauss E. (2016) Anterior Cruciate Ligament Injuries in Females: Risk Factors, Prevention, and Outcome, Bull Hosp Jt Dis, Vol 74 (1)
  • Herzog et al. (2020) Oral contraceptive use and anterior cruciate ligament injury: comparison of active comparator new user cohort and case-control study designs, Inj Epidermiol, Vol 7, Issue 1 
  • Hewett T.E,  Zazulak B.T. , G.D. Myer (2007) Effects of the menstrual cycle on anterior cruciate ligament injury risk: A systematic review, American Journal of Sports Medicine, Volume 35, pp. 659-668
  • Lopes M. et al (2020) Effects of the FIFA 11+ on injury prevention in amateur futsal players, Scand J Med Sci Sport, Vol 30 (8) 
  • Nilstad A. et al (2023) Kiss goodbye to the ‘kissing knees’: no association between frontal plane inward knee motion and risk of future non-contact ACL injury in elite female athletes, Sports Biomechanics, Volume 22 (1
  • Parsons J.L, Cohen S.E. and Bekker S. (2020) Anterior cruciate ligament injury: towards a gendered environmental approach, BJSM, Vol 55 (7)
  • The female ACL: Why is it more prone to injury?, J Orthop, Volume 13 (2) 
  • Wetters  N. et al. (2016) Mechanism of Injury and Risk Factors for Anterior Cruciate Ligament Injury, Operative Techniques in Sports Medicine, Volume 24, Issue 1, March 2016, Pages 2-6
  • Q-Angle image: http://www.kcchampionperformance.com/news/2016/3/9/kx8hq9n3wmbt2pbqy683hisu4y1xm4
  • Sam Kerr ACL image: https://www.theguardian.com/football/2023/may/08/sam-kerr-scare-puts-spotlight-on-injured-matildas-ahead-of-world-cup
  • Getty Images: https://www.afl.com.au/aflw/news/1002765/scans-confirm-acl-blow-for-demons-good-knee
  • AAP/AP: https://www.abc.net.au/news/2016-12-19/top-womens-sport-performances-in-2016/8113420
  • Female Hormone Cycle image: https://womeninbalance.org/about-hormone-imbalance/