While both men and women* have anterior cruciate ligament (ACL) injuries, research has shown that women experience two to eight times more of these injuries than men. Vehniah Tjong, MD, an orthopaedic sports medicine surgeon at Northwestern Medicine, explains the reason behind this gender-based difference. 

Understand the Injury

The ACL is one of four major ligaments in the knee that connect the thighbone and shinbone. Its primary role is to control movements involving quick stops and changes in direction. When playing sports that require pivoting (such as soccer, basketball, football or tennis), the ACL is a key ligament and can be vulnerable to injury. Although you can injure the ACL during a collision, most tears of this ligament are from noncontact injuries.

“If you tear your ACL, you may lack the ability to control any cutting or pivoting through the knee,” says Dr. Tjong. Injured ligaments are graded from mild to severe:

• Grade I: This is a mild injury with tiny tears. The ligament is slightly stretched but still able to help keep the knee joint stable.
• Grade II: The ligament is loose and considered a moderate injury with a partial tear.
• Grade III: This is a severe injury with a complete tear of the ligament, and the knee joint is unstable.

The majority of ACL injuries are Grade III.

Know the Risk Factors

ACL injuries occur for many reasons, but there are three main reasons why they’re more common in women:

• Anatomy: Women generally have wider hips compared to men and are often more knocked-kneed, which means their knees tend to tilt inward. This alignment alters the knee joint, increasing the risk of ACL injuries during movements such as jumping, pivoting and landing. The ACL tissue is also typically thinner in women, so it takes a less force to tear.
• Biomechanics: When women land, it’s usually in an upright posture, resulting in straighter knees and less core engagement. This is different from men who usually land with bent knees and with more core engagement.
• Hormones: Research shows that the elasticity of collagen in the knee is impacted throughout different stages in the menstrual cycle, resulting in a higher risk of ACL injury. 

Treatment Options

The treatment options for ACL tears are the same, regardless of your gender. If there is a complete tear of the ACL, it will likely not heal on its own. This is primarily due to the ACL being immersed in synovial fluid, a liquid within the knee, and the ligament’s limited blood supply, which can prevent the fibers from coming together to heal. 

For minor ACL injuries, there are nonsurgical treatments, such as wearing a leg brace for protection, in addition to undergoing physical therapy. However, for severe ACL injuries, surgery is an option.

Dr. Tjong says that when an ACL is completely torn, surgeons will use a donor ligament or tendon — typically your own hamstring tendons, quad tendon or patellar tendon — to replace it. During that surgery, associated injuries, such as meniscal tears, are also addressed.

“Ultimately, the primary goal of the surgery — especially in the younger population — is to fully restore their ability to return to playing at the same level they were before the injury,” Dr. Tjong explains.

Reduce Your Risk

The average time for an ACL tear to heal after surgery is nine to 12 months, and you’re six times more likely to have a second ACL injury once you’ve had one ACL injury, but there are ways to prevent future injuries.

Dr. Tjong suggests these tips for safe exercise and a healthy ACL:

• Train consistently: Complete strength and flexibility exercises during the off-season to improve your balance and coordination.
• Practice your landing skills and direction changes: Not bending your knees during directional shifts or landings after a jump can increase your chances of an ACL injury. Mechanics are important!
• Warm up before engaging in activity: Incorporate sport-specific exercise and give yourself time to stretch to prevent muscle strains.
• Strengthen muscles: Focus on strengthening the muscles in your lower body and core. A strong core and hips can help you improve your balance, while strong hamstrings and quadriceps work together to move your leg.

Regardless of your level of fitness, consult with a physician before starting a sport to ensure you are mentally and physically prepared.

*Scientists do not always collect information from participants about gender identity. To avoid misrepresenting the results of this research, we use the same terminology as the study authors.