Introduction
When we think of preventing sports injuries, we usually picture strength training, physiotherapy, or the right footwear. But what if your sports bra also played a role in protecting your knees? Recent studies suggest that breast support, or lack thereof, can directly influence anterior cruciate ligament (ACL) injury risk in active women.
This blog explores the science behind this surprising connection, what it means for female athletes, and how the right bra could act as protective gear, not just for your chest, but for your whole body.
Why ACL Injuries Matter in Women’s Sports
ACL injuries are among the most common and devastating injuries in sport as they are often career-ending. According to The British Journal of Sports Medicine, female athletes are up to six times more likely to suffer an ACL tear than men in comparable sports. Recovery can take 9 to 12 months, and many athletes never return to their previous level of performance.
“ACL injuries can be career-threatening and are associated with increased risk of developing knee osteoarthritis in future life” – Bone & Joint Open (2023)
Well-known examples include female footballers such as Alexia Putellas, and Olympic athletes like Courtney Frerichs, who have had seasons or entire careers cut short. But until recently, few people thought to ask whether breast biomechanics might be linked to these injuries.
How Breast Movement Affects Landing Mechanics
Breasts naturally move in a figure-eight pattern during running and jumping. Without proper support, this motion can throw off balance and landing mechanics.
Figure 6. Breast movement trajectories of body (solid line) and breast (dotted line) with sports bra in one stride of running in the medial/lateral direction.
Methods of studying breast motion in sports bras: A review - Scientific Figure on ResearchGate. Available from: https://www.researchgate.net/figure/Breast-movement-trajectories-of-body-solid-line-and-breast-dotted-line-with-sports_fig6_258195902
A 2022 study in the Journal of Applied Biomechanics found that low breast support led to riskier landing mechanics in female athletes:
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Greater peak knee flexion (bending)
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Higher inward knee valgus angles (knees bend inward)
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Increased valgus moments (strain on the ACL
Knee frontal-plane projection angles (FPPA) comparing a non-injured limb (A) and an ACL-reconstructed limb (B), illustrating higher inward knee valgus angles.
Ho, Hsuan-Yu, and Murata, Atsushi. “Asymmetries in the Dynamic Valgus Index After Anterior Cruciate Ligament Reconstruction.” International Journal of Environmental Research and Public Health 18, no. 13 (2021): 7047. MDPI. https://doi.org/10.3390/ijerph18137047
Meanwhile, high-support bras were associated with:
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Safer glute and core flexion during landing
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Reduced knee strain
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More controlled landings
In other words: less breast support = more bounce = more risk to your knees.
This connection between breast support and ACL injury risk is particularly important for women with larger breasts. The study highlighted that cup size influences the degree of impact on biomechanics. More breast motion can mean greater changes in landing technique and therefore higher ACL injury risk if support is inadequate.
Hormonal fluctuations and anatomical differences already put women at higher risk of ligament injuries. Combine this with poor breast support and the odds stack even higher against the athlete.
“We found that inadequate breast support altered lower limb biomechanics in ways that have been linked to an increased risk of ACL injury.” – Fong et al., 2022
Sports Bras as Protective Gear
Most people see sports bras as underwear. But based on the science, it should be viewed as protective sports equipment, much like how shoes protect the feet and ankles, and helmets protect the head.
Sports bras - when properly designed - protect not only the breasts but also movement efficiency and injury prevention
Practical Implications for Female Athletes
For athletes, this isn’t just a comfort issue, it’s a performance and injury-prevention issue. Here are some key takeaways:
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Choose encapsulation + compression bras: These minimise breast movement while keeping the chest stable.
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Look for adjustability: Adjustable bands and straps ensure a snug, supportive fit without restricting breathing.
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Consider your breast volume: the larger your cup, the more support you’ll need for biomechanical stability; opt for high support bras.
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Test it out: don’t just try a bra standing still. Jump, jog, and land in it before deciding.
The Future of Women’s Sportswear
Sports science is only beginning to understand how breast biomechanics affect overall athletic performance and injury risk. As more studies emerge, we hope to see sports bras recognised not just as apparel, but as essential protective gear for female athletes at every level. This is exactly what we at Tigers Eye advocate for. By designing bras that combine scientific research, biomechanics, and real-world testing we are changing and challenging how we think about women’s performance gear.
Conclusion
The link between breasts and ACL injuries may sound surprising at first but the science is clear: sports bras play a vital role in protecting knees, posture, and long-term athletic performance.
For women in sport, especially those at high levels or doing high-impact activities, the right sports bra is not just a matter of comfort. It’s about stability, protection, but also career & health longevity.
So next time you gear up for training, don’t forget a proper sports bra.
References
ABC News. (2024, April 23). Wearing the wrong bra could put you at a greater risk of a knee injury, study suggests. ABC News. https://www.abc.net.au/news/health/2024-04-24/breast-support-bra-choice-linked-to-risk-of-acl-knee-injury/103736994
Fong, D. T.-P., Ng, G. Y. F., Scurr, J., & Hedger, W. (2022). Greater breast support alters trunk and knee joint biomechanics commonly associated with anterior cruciate ligament injury. Frontiers in Sports and Active Living, 4, 861553. https://doi.org/10.3389/fspor.2022.861553
Ho, H.-Y., & Murata, A. (2021). Asymmetries in the dynamic valgus index after anterior cruciate ligament reconstruction. International Journal of Environmental Research and Public Health, 18(13), 7047. https://doi.org/10.3390/ijerph18137047
Mancino, F., Kayani, B., Gabr, A., Fontalis, A., Plastow, R., & Haddad, F. S. (2024). Anterior cruciate ligament injuries in female athletes: Risk factors and strategies for prevention. Bone & Joint Open, 5(2), 94–100. https://doi.org/10.1302/2633-1462.52.BJO-2023-0166
Scurr, J. C., White, J. L., & Hedger, W. (2010). The effect of breast support on the kinematics of the breast during the running gait cycle. Journal of Sports Sciences, 28(10), 1103–1109. https://doi.org/10.1080/02640414.2010.497542
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