Why Are Females at a Higher Rate of ACL Injury?

By: Stephanie McDougal, PT, DPT, Clinical Supervisor-Souderton
The Physical Therapy & Wellness Institute

We have all heard that females are at a higher rate of a non-contact Anterior Cruciate Ligament (ACL) injury/tear. But why? Well, there are many reasons as to why women have a higher incidence of tears, but there are many steps one can take to decrease the risk of an ACL injury.

ACL Injury
ACL Injury. Digital image. Mayo Clinic, n.d. Web. 21 Feb. 2017.

First, let's get on the same page about what the ACL is, prevalence of an ACL injury, and how it is commonly injured. ACL tears are among the most common knee injuries, with over 100,000 tears in the US occurring annually1. The ACL is responsible for 85% of the restraining force to anterior (forward) shear and medial rotation of the tibia (lower leg bone) on the femur (upper leg bone)1. This means that during high demand sports that involve planting, cutting, jumping, stopping suddenly/deceleration or changing directions quickly you are putting a lot of stress on the ACL. Sports where ACL injuries occur most often include soccer, basketball, football, tennis, downhill skiing, volleyball, and gymnastics2. If you don't have the muscle strength and neuromuscular control of your muscles an ACL injury can occur.

Woman landing with legs straight Woman landing with one knee facing inward
Coldham, Lewis. Lewis Coldham Strength and Conditioning. Digital image. Foundation skills and motor quality development Part 2. N.p., 24 Feb. 2014. Web. 21 Feb. 2017.

ACL injuries occur with a four to six fold greater incidence in females compared to male athletes playing the same high-risk sports3. So why are females more prone to an ACL injury than their male counterparts? Studies have shown that there are at least 4 reasons that women have a higher incidence of non-contact ACL injuries. First, is the difference between female's quadriceps (front thigh muscle) to hamstring (back thigh muscle) ratio in strength. Women tend to have weaker hamstrings in relation to their quadriceps and also use their quadriceps more dominantly when performing jumping and deceleration activities. Because of this lack in hamstring use and strength, female athletes are missing out on the hamstrings helping control some of that shear force on the tibia and therefore reducing the stain on the ACL. Secondly, biomechanical analysis has shown that women and men tend to land differently during jumping and landing activities. Women tend to have a collapse of their knees inward, land with a more straight leg (not absorb the ground), and land with weight unequally distributed3. These changes in landing and jumping biomechanics put more stress on the ligamentous system of the knee. Furthermore, some doctors think that women are more likely to have an ACL injury because of the differences in the amount of circulating hormones such as estrogen and relaxin. Both of these hormones are responsible for ligaments strength and flexibility and the fluctuation of hormones may influence the function of different tissues. Finally, it is suspected that the Q Angle or quadriceps angle in females predisposes them the ACL injuries. The Q angle is essentially the line of pull of the quadriceps in relation to the pelvis5. Women tend to have a greater Q angle that puts a more medial (midline) force to the knee during weight bearing activities and if she does not have strong enough hip abductors then it can lead to an unstable knee during cutting, jumping and landing.

So now that we know the odds are not in our favor, what can we do? There are a couple steps you can take now to help lower your risk of an ACL injury/tear. As we discussed previously having weak hamstrings and hip abductors can be part of the risk stratification, so increasing your hamstring and lateral hip muscle strength is a good place to start. Also there has been significant research done on retraining proper jumping and agility through jumping and landing programs and speed and agility training for neuromuscular control and quick firing of muscles groups for improved stabilization.

Not sure if you need help or exhibit these risk factors of improper muscle control, strength, or motor control during jumping, cutting, and landing? Speaking with a physical therapist or other sports medicine professional is a good place to start. Contact us at The Physical Therapy & Wellness Institute and our clinicians can do a full evaluation to identify weak muscles areas, examine your jumping and landing performance and identify ways to help you improve your training and thus prevent injury.

References

  1. "Anterior Cruciate Ligament." Wikipedia, 20 Dec. 2016. Web. 21 Feb. 2017. https://en.wikipedia.org/wiki/Anterior_cruciate_ligament.
  2. "ACL Injury." Mayo Clinic, 12 Jan. 2017. Web. 21 Feb. 2017. http://www.mayoclinic.org/diseases-conditions/acl-injury/manage/ptc-20167405.
  3. Osbourne, Maria. "Why Do Females Injure Their Knees Four to Six Times More Than Men…And What Can You Do About It?" ;University of Colorado Hospital. N.p., Summer 2012. Web. 21 Feb. 2017. http://www.ucdenver.edu/academics/colleges/medicalschool/departments/Orthopaedics/clinicalservices/sportsmed/Documents/WISH_SPORTSMED_Female%20Knee%20Injuries%20and%20ACL.pdf.
  4. Dehghan, F et al. "The Effect of Relaxin on the Musculoskeletal System." Scandinavian Journal of Medicine & Science in Sports 24.4 (2014): e220–e229. PMC. Web. 21 Feb. 2017.
  5. Pagare, Venus. "'Q' Angle." Physiopedia. N.p., n.d. Web. 21 Feb. 2017.
  6. MacCambridge, Teri, and Gregory Myer. "Preventing ACL Injuries." Stop Sports Injuries. N.p., n.d. Web. 21 Feb. 2017.
  7. Coldham, Lewis. Lewis Coldham Strength and Conditioning. Digital image. Foundation skills and motor quality development Part 2. N.p., 24 Feb. 2014. Web. 21 Feb. 2017.
  8. ACL Injury. Digital image. Mayo Clinic, n.d. Web. 21 Feb. 2017.