Why are females more at risk for ACL injuries?

Dr. Jennifer A. Baima, MD
Neuromuscular Medicine Specialist

We are still learning about how injuries to the ligaments are different in women and men. One theory is that women have looser ligaments than men due to our different hormones. Women are clearly subject to different neuromuscular imbalances than men due to our wider hips and the more narrow position of our knees. Neuromuscular imbalance means that some of the weaker muscles are not being used in the way that they should be for optimal performance. Overall, the female body responds differently to exercise than the male body. Gender-specific training will likely decrease these injuries. ACL tear may occur due to many reasons such as a more narrow notch where the ACL passes through the upper thigh bone, higher estrogen levels, and neuromuscular imbalances. We cannot change the shape of our thigh bones or our hormones, but we can do something to correct these neuromuscular imbalances through physical assessment and exercise prescription. Stress fractures are more common in women from the hormonal influence of estrogen on bones. When we exercise too much, it is harder to make and store estrogen in fat cells. An imbalance in nutritional intake and activity output can play into not having enough estrogen. It is important to have this evaluated to get the most out of your exercise training.

In the battle of the sexes, women win the ACL division in a walk. (Or a hobble, more aptly). Women are up to eight times more likely than men to tear their anterior cruciate ligaments (ACL). The looser construction of the female knee-and overall weaker skeleton-can compromise stability and predispose women to ligament tears.

The injuries are also linked to hormonal changes around the time of menstruation, so female high school, collegiate, recreational, and professional athletes end up suffering many more tears than men.

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Females are more likely to sprain their ACL (anterior cruciate ligament) than males due to many physiological differences and factors. The ACL itself is smaller and more lax or loose in females than in males; some other areas of flexibility or laxity are in the anterior knee and the knee joint itself. Females also have less muscular structure and strength than males which can lead to knee joint instability; as well as a different angle that the femur connects with the tibia, causing a greater likelihood of knee and other lower limb injuries. Hormonal and menstrual influences also play a role in how females are more likely to sprain their ACL than males.

This answer provided for NATA by Loras College.

According to the National Academy of Sports Medicine an estimated 80,000 to 100,000 anterior cruciate ligament (ACL) injuries occur annually in the general U.S. population. Approximately 70 to 75% of these are of the noncontact type. In addition, Researchers have estimated healthcare costs to be approximately $2.5 billion annually for ACL injuries.

Across multiple sports, the overall incidence of ACL injuries is pretty stable between genders. However, in sports where both men and women compete (I.E. soccer, basketball, ECT), the injury rate is higher in women. There are some theories, but unfortunately, no one knows exactly what causes the increased risk of ACL tears in women. More investigation is constantly taking place to better answer this question. Below are some of the proposed reasons for the increased risk of ACL tears in women.

    There are many anatomical differences between men and women, including pelvis width leading to a larger Q-angle; this is the angle at which the femur (upper leg bone) meets the tibia (lower leg bone). On average this angle is degrees greater in women than in men. It is thought that this increased angle places more stress on the knee joint, as well as leading to increased foot pronation and poor patellar tracking in women.
    it is known that the ACL has hormone receptors for estrogen and progesterone, and it has been thought that hormone concentration could play a role in ACL injuries. Studies have shown some differences in rates of ACL injury during different phases of the menstrual cycle. However, there has been some conflicting data, and the effect of hormone concentration on ACL injury risk has yet to be defined.
    Stability of the knee is dependent on different factors. The two most important are the static and the dynamic stabilizers of the knee. The static stabilizers are the major ligaments of the knee, including the ACL. The dynamic stabilizers of the knee are the muscles and tendons that surround the joint. Women have been found to have differences in biomechanical movements of the knee seen when pivoting, jumping, and landing. Dysfunctional movements during these activities often lead to an ACL injury.

Females are more at risk for anterior cruciate ligament (ACL) injury in the knee for a few reasons. First, they have some anatomic variables that contribute to this. In general, females have an increase in joint laxity, meaning their joints are looser. So, this is a predisposition for ACL tears. Second, there is a noticeable difference in neuromuscular control, meaning the body’s ability to control the muscles and the joints in things like jumping and running activities. Lastly, there are some anatomic variables with the width of the female hip and the notch within the knee where the ACL lives. Those are all things that increase the risk of ACL tears in females compared to males.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.