PAMF Health Blog

Be Well, Be Well Informed

How to Prevent ACL Tears in Teens

Posted on Oct 22, 2014


ACL tears happen suddenly, almost without fail, each high school sports season. A teenager jumps or pivots fast to get the ball. The teen may feel a pop in the knee, but usually can walk off the field. Within 24 to 48 hours the teen’s knee is severely swollen.

And if your teenage athlete is a girl, her risk of tearing the anterior cruciate ligament (ACL) is four to six times greater than a boy’s. Why? “That’s the hot question right now,” says Sally Harris, M.D., a pediatric sports medicine doctor at the Palo Alto Medical Foundation. At first, researchers thought hormones and girls’ body structure increased their risk. But studies now indicate those are minor points. More likely, Dr. Harris says, girls are at greater risk for ACL tears because of two factors, both preventable:

  • Biomechanics: Girls tend to hold their bodies more upright than boys when they jump, cut and pivot. They also tend to let their knees turn inward into a knock knee position.
  • Muscle imbalance in the thighs: Girls’ hamstrings – the muscle in back of the thigh – are generally weaker than their quadriceps, the main muscle in front of the thigh. Their quadriceps can overpower their hamstrings, which puts pressure on the knee.

“There are successful prevention programs out there, and research shows they can prevent ACL tears in girls by over 80 percent,” says Dr. Harris. Unfortunately, “most coaches are not aware of the prevention programs and don’t incorporate the techniques into their training programs.”

What can parents and teen athletes do? “Girls who strengthen their hamstrings and learn how put their knee directly over their foot can protect themselves a lot,” Dr. Harris says.

  • To start, she recommends viewing and printing slides 13-29 of Vanderbilt University Orthopaedic Institute’s highly regarded ACL Prevention Program. The slides show girls specific agility drills, stretches and exercises to help prevent ACL tears.
  • Follow that program three times a week.
  • If your teen has difficulty doing the workout on her own, find a physical therapist to work with her.

A torn ACL cannot heal itself, like some ligaments in the body. Young athletes who want to stay active throughout their life usually require surgery.

“The surgery is very successful in stabilizing the knee and restoring function. But we know that if you’ve torn your ACL once, you have a higher risk of premature arthritis and tearing the ACL again in the same knee or the opposite knee,” Dr. Harris says.

Prevention is a far better solution. Dr. Harris envisions the day when ACL tear prevention programs are incorporated into every team’s training and drills. “It should be. It could be. And I think it’s a coming thing.”

HarrisSally Sally Harris, M.D., is board-certified doctor in sports medicine and pediatrics at the Palo Alto Medical Foundation