What are ACL Injuries, and How Do They Impact Women

When discussing sports injuries, ACL tears often surface as one of the most notorious culprits. While these injuries are prevalent in both males and females, research has shown that women are disproportionately affected. In fact, 1 in 29 female athletes will rupture their ACL, whereas 1 in 50 male athletes will suffer the same injury (1). So, what is an ACL injury, and why are women more susceptible to these types of knee injuries?

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Understanding the Basics: The ACL

The Anterior Cruciate Ligament, commonly called ACL, is a pivotal ligament within the knee. Connecting the femur (thigh bone) to the tibia (shin bone), the ACL plays a crucial role in stabilizing the knee, particularly during activities involving twisting or rapid changes in direction. This is supported by the medial collateral ligament (MCL), which stops the knee from bending inwards.

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Are ACL Injuries Common in Women?

ACL injuries are common in women and often more frequently than in men (1), especially in athletic activities that involve jumping, cutting, and pivoting (2), such as basketball, soccer, and volleyball. Prevention programs focusing on neuromuscular training, strengthening exercises, and proper technique have been developed and shown to reduce the incidence of ACL injuries in women athletes.

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How ACL Injuries Occur

Typically, ACL injuries arise from (3):

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• Quick directional changes
• Sudden halts or decelerations
• Awkward landings post-jump
• Direct impacts, like a tackle in football

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Interestingly, female athletes tend to sustain ACL injuries 2 to 6 times higher than their male counterparts (4, 5), especially in sports like basketball, soccer, and volleyball. 

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But why?

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Anatomical Differences: The female pelvis is generally wider, leading to a greater angle where the femur meets the tibia, often called the "Q-angle". This range of motion can increase the stress on the knee, making ACL injuries more likely.

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Hormonal Factors: Some studies suggest that fluctuating hormone levels during a woman's menstrual cycle impact ligament elasticity and strength, potentially elevating the risk of injury. (4). Ovulation and pregnancy can increase joint laxity, which can also increase the ACL risk.

Biomechanics and Movement Patterns: Women, on average, may demonstrate different landing and cutting mechanics than men. For instance, they might land with a more extended knee or rely more on their quadriceps, which can strain the ACL more.

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Muscle Strength and Conditioning: Disparities in muscle strength and coordination, especially between the quadriceps and hamstrings, can influence the stability of the knee joint and, subsequently, the risk of injury.

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Symptoms and Diagnosis

Individuals with an ACL injury often experience (6):

• A pronounced "pop" at the injury's moment 
• Immediate pain and swelling 
• Restricted motion range
• Joint tenderness
• Difficulty or discomfort during walking
• A professional diagnosis typically involves a physical examination and imaging tests like MRI.

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Treatment and Recovery

Treatment varies based on the injury's severity and the individual's goals. While some might benefit from physical therapy alone, others, especially those aiming to return to high-demand sports, may require surgery. 

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Rehabilitation is essential regardless of the treatment route. It aids in regaining strength, flexibility, and overall function. While recovery durations vary, with persistence and the proper guidance, most can return to their desired activity levels.

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Can you still walk with a damaged ACL?

The anterior cruciate ligament (ACL) is crucial for knee stability. After injuring the ACL:

• Immediate Aftermath: Sharp pain, swelling, and potential "pop" sensation can make walking difficult.
• Post-Injury Walking: Once initial swelling decreases, walking is possible, but pivoting or sudden direction changes might feel unstable.
• Risks: While you can walk, there's potential for further knee damage or causing harm to other joint structures.
• Medical Consultation: If an ACL injury is suspected, seek medical advice. Diagnosis often involves imaging, like MRI.
• Treatment: Depending on severity, treatment ranges from physical therapy to surgery.

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In short, while walking with a damaged ACL is possible, it's essential to be cautious and consult a medical professional.

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ACL and the Menstrual Cycle

ACL injuries have been observed to have a connection with the menstrual cycle in females, suggesting a potential influence of hormonal fluctuations on knee stability and injury risk (7). 

A substantial review of studies encompassing 68,758 participants found that among women not using hormonal contraception, the luteal phase was the least associated with ACL injuries. This suggests that hormonal fluctuations during the menstrual cycle could influence the risk of ACL injuries (8)​​.

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Another study highlighted that a significantly greater number of ACL injuries occurred on days 1 and 2 of the menstrual cycle. This period typically corresponds to the early follicular phase when estrogen and progesterone levels are at their lowest. The correlation of salivary sex hormone levels with the reported cycle day further supports the notion that hormonal changes can impact the likelihood of ACL injuries in female athletes​​ (9).

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Moreover, previous studies have shown an increased risk of ACL injuries during the late follicular and ovulatory phases of the menstrual cycle. However, it is important to note that the data across different studies has not always been consistent, indicating the complexity of understanding the precise relationship between menstrual cycle phases and ACL injury risk (10)​​.

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Empowering Women in Sports

Understanding women's unique risks can pave the way for improved training programs, injury prevention strategies, and overall awareness. As we push for gender equality in sports, we must address these physiological differences and advocate for tailored approaches to female athletic training and care. 

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Products such as the Wild.AI coach dashboard can help coaches monitor the cycles of the women they train. This allows coaches to see the best times to train hard and when to avoid activities that might cause ACL injuries.

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Conclusion

ACL injuries, while common, have a disproportionate impact on female athletes. When an athlete experiences a knee injury, it can massively set back training goals and sometimes affect the enjoyment of athletic activity. By understanding the reasons and working towards specific preventive measures, we can ensure a safer and more inclusive sports environment for all.

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References

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1. Montalvo, A.M., Schneider, D.K., Yut, L., Webster, K.E., Beynnon, B., Kocher, M.S., Myer, G.D., 2019. “What’s my risk of sustaining an ACL injury while playing sports?” A systematic review with meta-analysis. British Journal of Sports Medicine 53, 1003–1012. https://doi.org/10.1136/bjsports-2016-096274 

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2. Montalvo, A.M., Schneider, D.K., Yut, L., Webster, K.E., Beynnon, B., Kocher, M.S., Myer, G.D., 2019. “What’s my risk of sustaining an ACL injury while playing sports?” A systematic review with meta-analysis. British Journal of Sports Medicine 53, 1003–1012. https://doi.org/10.1136/bjsports-2016-096274 

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3. Arendt, E.A., Agel , J., Dick, R., 2019. Epidemiology of Anterior Cruciate Ligament (ACL) Injury among Collegiate male athletes in Football and volleyball. Journal of Nursing & Healthcare 4. https://doi.org/10.33140/jnh.04.02.6 

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4. Ireland, M.L., 2002. The female ACL: why is it more prone to injury? Orthopedic Clinics of North America 33, 637–651. https://doi.org/10.1016/s0030-5898(02)00028-7 

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5. Myer, G.D., Ford, K.R., Hewett, T.E., PhD, 2006. Preventing ACL injuries in women. The Journal of Musculoskeletal Medicine 12–38. 

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6. NHS, 2020. Display Patient Information Leaflets [WWW Document]. University Hospitals Plymouth NHS Trust. URL https://www.plymouthhospitals.nhs.uk/display-pil/pil-anterior-cruciate-ligament-3962/ (accessed 12.1.23). 

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7. Hutchinson, A., 2021. How Your Menstrual Cycle Affects Your Injury Risk. Outside Online. https://www.outsideonline.com/health/training-performance/menstrual-cycle-injury-risk/

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8. Herzberg, S.D., Motu’apuaka, M.L., Lambert, W., Fu, R., Brady, J., Guise, J.-M., 2017. The Effect of Menstrual Cycle and Contraceptives on ACL Injuries and Laxity: A Systematic Review and Meta-analysis. Orthopaedic Journal of Sports Medicine 5, 232596711771878. https://doi.org/10.1177/2325967117718781 

9. Slauterbeck, J. R., Fuzie, S. F., Smith, M. P., Clark, R. J., Xu, K., Starch, D. W., & Hardy, D. M. (2002). The Menstrual Cycle, Sex Hormones, and Anterior Cruciate Ligament Injury. Journal of athletic training, 37(3), 275–278.

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10. BJSM, 2021. Does injury incidence really change across the menstrual cycle? Highlighting a recent key study [WWW Document]. BJSM blog - social media’s leading SEM voice. URL https://blogs.bmj.com/bjsm/2021/04/05/does-injury-incidence-really-change-across-the-menstrual-cycle-highlighting-a-recent-key-study/ (accessed 12.1.23).