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Teen Health 411
Teen Health 411

Sports and Injuries in Teens - ACL Injuries

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I am learning a huge amount about sports and injuries this summer while working with the teen writers for the We're Talking Teen Health site at the Palo Alto Medical Foundation. I am by no means an expert in sports, but I think parents and teens need to be aware that the rate of injury in teen athletes is going up, but injuries can be prevented.

This week we interviewed a doctor about ACL (anterior cruciate ligament) injuries in the knee and I wanted to share what I learned.

How does this injury happen?
This injury is specific to sports that involve starting, stopping, pivoting and turning with some speed – particularly in sports like basketball, soccer, volleyball, football, field hockey, skiing, and lacrosse. There are primarily two ways the injury happens:
  • landing on an over-straight (hyper-extended) knee, and
  • with a foot planted a person pivots inward (internal rotation) without the foot coming, too.
This can happen in contact and non-contact injuries.

How is this injury usually diagnosed?
Usually there is significant swelling, and there are only a few injuries with this amount of swelling; there is an exam maneuver that is done to test for looseness of the ligament (if it is firm it is not torn, and if it is loose, it is likely torn), and an MRI is usually done to confirm the diagnosis. An x-ray will not help because it only shows the bones. The MRI will also identify whether the meniscus (shock-absorbing cartilage) was damaged (torn) during the injury.

How is this injury typically treated?
If the injury is in an adolescent who intends to go back to sports in which s/he will need to do pivoting, they will need surgery. If the injury is in an older person who jogs, bikes, or swims, activities that do not require the pivoting, the injury may not need to be repaired. If the meniscus was damaged, then during surgery the doctor will smooth it out so there is not a frayed area that will cause irritation, or sew it back together, depending on the nature of the tear. The doctor will try to preserve as much of the meniscus as possible given that it is the shock-absorber for the knee.

What is the recovery like if this injury is treated with surgery?
A person will need to be on crutches for about one week, have physical therapy twice a week for a month, and then they can start biking, jogging, swimming, but need to wait approximately four months before going back to the sport that requires any pivoting or turning. This is because the surgery includes adding some new ligament, which will get weaker before it gets stronger and takes a long time to heal.

How can teens prevent an ACL injury?
This is really a hot topic because ACL tears are much more common in female than male athletes. In fact, it is not uncommon during a single season that one out of 12 females on a team will experience an ACL injury.

There has been a lot of research done about why this is the case, and the results suggest that it is not because of the physiology or hormones of the female body, as was previously hypothesized, instead it is more likely to be:
  • muscle imbalance in the thigh as the quadriceps muscles overpower the hamstring muscles which need to work together to straighten (extend) and bend (flex) the leg; or
  • the way female athletes move during their sport, remaining more upright with their knees less bent than their male counterparts that puts the ACL in a vulnerable position.
In addition, you may have heard someone say “you run like a girl,” which usually means that when a person runs, their feet kind of go out, and knees bend in, instead of the knees staying straight over the foot, which is how girls tend to run (post-puberty), without training.

Prevention of this injury should include 15 minutes several times a week training to learn how to:
  • stop and start keeping the knee straight over the foot, avoiding the knock-knee position which makes the ACL vulnerable,
  • standing on a block and jumping, keeping the knee straight over the foot, and
  • hamstring strengthening exercises.
Photo credit: goldberg
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About the Author

Dr. Brown is a developmental psychologist specializing in adolescent health.

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