What is a Torn ACL? 

The ACL (anterior cruciate ligament) is 1 of the 4 main ligaments that attach the thigh bone (femur) to the shin bone (tibia). The ACL keeps the shin bone in place and the knee from buckling (“giving out”) during physical activity. 

An ACL tear is a serious knee injury. It’s common in people who do sports that involve running combined with pivoting and jumping, such as football, basketball, and soccer. A damaged ACL will not heal on its own. 


Symptoms of a torn ACL can include:

  • A popping sound when the injury happens
  • Intense knee pain
  • An unstable knee and won’t hold your weight
  • Swelling in the knee within a few hours after the injury

A mild injury may not have symptoms.

When to See a Doctor

See your healthcare provider if you injure your knee. If it hurts, don’t put weight on it. If your knee is swollen, put ice on it until you get to the healthcare center. 


An ACL tear is most commonly caused by:

  • Quickly changing direction, pivoting, or slowing down suddenly while changing direction. This is common in sports like basketball, soccer, tennis, and gymnastics. These injuries are more common in women than men. The reason for this is not clear.
  • Direct injuries to the knee that force it to over-extend or push sideways. This is common in football, rugby, or car crashes.

Diagnosis and Tests 

To find out if an ACL injury is the cause of your symptoms, your healthcare provider can:

  • Do a physical exam of your knee.
  • Order an imaging test called an MRI. This test allows the healthcare provider to see injuries to the ligaments and muscles.

Treatments & Prevention


An ACL injury will not heal on its own. Your healthcare provider may recommend:

  • Physical exercises, called rehabilitation exercises, or “rehab.” This will help strengthen the muscles around your knee.
  • Surgery. If your injury is severe or is still unstable after rehab, you may need surgery. In ACL reconstruction surgery, a surgeon will replace the torn ACL with new tissue. This can be tissue taken from another part of your leg or from another person. After surgery, you’ll need to do more rehab exercises.

You and your healthcare provider will decide together if surgery is the best plan for you. This decision is based on your age, activity level, and other health conditions. Ask about how your outcomes might be different with or without surgery. Ask how these might affect your ability to do the activities you want to do.

Locations Near

Add an address to see locations nearby