What is an anterior cruciate ligament (ACL) tear?

The anterior cruciate ligament (ACL) is one of the major stabilizing ligaments in the knee. A torn ACL does not heal on its own, and often leads to the feeling of instability in the knee.

The anterior cruciate ligament (ACL) is one of the large ligaments within the knee that help provide stability to the knee. If the ACL tears, the ligament fibers are torn either partially or completely. When the ACL tears, the tibia (calf bone) can move forward relative to the femur (thighbone). This is an unstable joint. The amount of instability depends on the size of the tear and how strong the surrounding muscles and ligaments are. If the ACL is completely torn and you are a very active person, it could lead to further knee injury to the cartilage, blood vessels and nerves.

The anterior cruciate ligament (ACL) is a ligament inside your knee that keeps your knee and shinbone in place. It's also the most commonly damaged knee ligament.

When a knee ligament like the ACL is torn, you may feel like your knee doesn't want to hold up. It's likely to give out on you when you turn corners or walk. It's very uncomfortable, and it puts the rest of the cartilage in your knee at risk of being damaged when your knee shifts out of place.

Basketball, football, soccer, downhill skiing and other aggressive sports where you're making cutting movements are a frequent cause of ACL tears. The most important thing for people to remember is that even if you have very well-developed muscles, you can tear your ACL. Professional athletes frequently tear their ACLs, so it's not an injury you can absolutely prevent.

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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.