Please note: This information was current at the time of publication but now may be out of date. This handout provides a general overview and may not apply to everyone. For regularly updated information on a variety of health topics, please visit familydoctor.org, the AAFP patient education website.

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What is the anterior cruciate ligament?

The anterior cruciate ligament (ACL; an-TE-re-or KROO-she-ate LIG-ah-ment) is a band of tissue that keeps the knee joint in place (see picture). It connects the femur (thigh bone) with the tibia (the main bone in your lower leg).

What causes ACL tears?

Your ACL can tear during a contact or noncontact injury. A contact injury can happen when your leg is firmly planted on the ground and something hits it from either side. Noncontact injuries happen when your knee is extended too far or when it twists too far. Activities with these types of movements include skiing, volleyball, basketball, soccer, football, and tennis.

How do I know if my ACL is torn?

If you hear a popping sound, followed by knee pain and swelling, you may have an ACL tear. You might also feel your knee giving out when you try to put weight on that leg. Your doctor will examine your knee to see if the ACL is torn. You may also need an x-ray or other scans.

How is it treated?

You should rest and put ice on your knee for 20 minutes every four hours for up to two days. Keep your knee raised when possible, and use anti-inflammatory medicine, such as ibuprofen (one brand: Motrin), for the pain and swelling. You can also wrap an elastic bandage around your knee to stop some of the swelling. It is important to do range-of-motion and strengthening exercises after the swelling starts to go down. Your doctor or a physical therapist can tell you what type of exercises to do.

You may need surgery to repair an ACL tear. During surgery, doctors take tissue from another part of your body to replace the torn ACL.

What can I expect after surgery?

You will need physical therapy to improve movement and strength in your knee joint. The recovery time is different for everyone.

How can I prevent an ACL tear?

There are exercise programs you can do. One is called “Prevent Injury, Enhance Performance.” It involves stretches and exercises of the muscles around the knee joint.

Where can I get more information?

Your doctor

AAFP's Patient Education Resource

American Academy of Orthopaedic Surgeons

Santa Monica Orthopaedic and Sports Medicine Group (Prevent Injury, Enhance Performance program)

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