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ACL Injury

The anterior cruciate ligament (ACL) is one of the knee joint's four major ligaments, which work together to coordinate function and promote stability. A ligament connects one bone to another. Running from the back of the femur (thighbone) to the front of the tibia (the larger long bone of the calf), the ACL prevents forward movement of the tibia and provides rotational stability to the knee.

ACL injuries commonly occur during exercise or sports, most often during a noncontact event, such as a quick change of direction in soccer. A smaller percentage of ACL injuries result from direct contact with another player or object. Several studies have shown that females have a higher incidence of this injury than males, especially in certain sports. It's been proposed that this is because of differences in physical conditioning, muscular strength, neuromuscular control and bone alignment, as well as women's looser ligaments and the effects of estrogen on ligament properties.

The classic ACL injury occurs when decelerating, stopping suddenly, twisting or jumping. People often hear or feel a pop at the moment of injury and sometimes experience a brief hyperextension of the knee joint. Immediately afterward, some people are able to continue their activity, but most are not. A few hours later, the knee will be considerably swollen.

Our Approach to ACL Tears

UCSF is committed to helping patients with ACL tears return to the highest level of activity possible, whether that means a daily walk or reporting for practice with the NFL. Our team includes orthopedic surgeons, primary care sports medicine doctors, physical therapists and athletic trainers. These specialists work together to tailor a treatment plan that supports each patient's needs and goals.

Awards & recognition

  • usnews-neurology

    Among the top hospitals in the nation

  • usnews-orthopedics

    One of the nation's best for orthopedic care

UCSF Health medical specialists have reviewed this information. It is for educational purposes only and is not intended to replace the advice of your doctor or other health care provider. We encourage you to discuss any questions or concerns you may have with your provider.