Signs and Symptoms

  • Young athletes who partially or completely tear their ACL may or may not have symptoms, depending on the severity of the injury.
  • Most kids report hearing a “pop’’ sound—which is the sound of the ligament tearing. 
  • When athletes tear their ACL, they sometimes report a sensation that their knee has "given out."
  • Often there is intense pain and swelling of the knee joint within 24 hours of the tear.

Who is at risk?

Teenage girls are four times more likely than boys to tear an ACL for reasons ranging from differences in body shape to hormones that loosen the ACL.


A child who injures a knee should stop all activity to prevent further injury and seek immediate medical care. In the meantime:

  • Keep the area iced for up to 20 minutes at a time.
  • Keep the knee elevated to reduce swelling.
  • Don’t allow child to put weight on the knee.

Surgery is often necessary. If the child is still growing, our surgeons will focus on making sure surgery doesn’t affect the growth plates.


At our doctor’s office or emergency room, a physical exam and imaging tests will determine if there is a knee injury and its severity. These tests can help diagnose an ACL injury:

  • Lachman test
  • Pivot-shift test
  • Anterior drawer test
  • X-rays may be used to determine if there are bone fractures in the knee; however, they can’t determine the extent of an ACL injury to the ligaments and muscles.
  • An MRI, which images tissue, can confirm a partial or complete ACL tear.

Rehabilitation and Recovery

After surgery, a child will need to use crutches and wear a full-leg brace for four to six weeks. Total recovery is a lengthy process that can take six months to a year.

Most kids will have to undergo physical therapy three times a week and do daily exercises at home to help the knee heal. Most sports will be off limits; although, some low-impact activities may be allowed, like swimming or bicycle riding.