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.
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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.
ACL Reconstruction Surgery
Considering ACL Reconstruction Surgery? Discover everything you need to know about preparation, the procedure itself and post-surgery recovery right here.
Preparing for ACL Surgery
The decisions you make and the actions you take before your surgery can be every bit as important as the procedure itself in ensuring a healthy recovery.
After ACL Surgery
Your rehabilitation program to restore range of motion to your knee begins the moment you wake up in the recovery room after ACL surgery. Learn more here.