Skip to Content
Home > Wellness > Health Library > Anterior Cruciate Ligament (ACL) Injuries
An anterior cruciate ligament (ACL) injury is a tear in one of the knee ligaments that join the upper leg bone to the lower leg bone. The ACL helps keep your knee stable.
When you twist, bend, or over-straighten your knee, you can injure your ACL. This can cause knee pain, swelling, and weakness. Rest and physical rehabilitation (rehab)—and sometimes surgery—are important to prevent a long-lasting knee problem.
ACL injuries range from mild, such as a small tear, to severe, such as when the ligament tears completely or when the ligament and part of the bone separate from the rest of the bone.
Current as of:
November 14, 2014
William H. Blahd, Jr., MD, FACEP - Emergency Medicine & Freddie H. Fu, MD - Orthopedic Surgery
How this information was developed to help you make better health decisions.
To learn more, visit Healthwise.org
© 1995-2015 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.
Our interactive Decision Points guide you through making key health decisions by combining medical information with your personal information.
You'll find Decision Points to help you answer questions about:
Get started learning more about your health!
Our Interactive Tools can help you make smart decisions for a healthier life. You'll find personal calculators and tools for health and fitness, lifestyle checkups, and pregnancy.
Feeling under the weather?
Use our interactive symptom checker to evaluate your symptoms and determine appropriate action or treatment.