Anterior Cruciate Ligament (ACL) injury | Symptoms & Causes

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How do ACL tears occur?

The ACL is typically injured during sports participation. Sports that involve frequent cutting and twisting motions, such as football, soccer, basketball, lacrosse and gymnastics, have relatively high rates of ACL injury.

The ACL can be torn when a player stops quickly, changes direction rapidly, lands after a jump or collides with other players. The athlete may hear a pop
when the ACL tears.

Anterior Cruciate Ligament ACL InjuryWhat factors increase risk of an ACL tear?

Teens are the most athletically active age group and have the highest risk of ACL injuries.

Teens who are especially at risk include those who play contact sports (such as football and hockey) and sports that involve cutting and pivoting (such as soccer, basketball, gymnastics and lacrosse).

Are girls more likely than boys to tear their ACLs?

Girls are five to eight times more likely than boys to tear their ACLs for several possible reasons:

•   Girls tend to put more stress on their ligaments, compared
    to their muscles, relative to boys, when playing sports.

•   At puberty, boys grow in height and develop their lower leg muscles at the same time. When girls grow, they don’t
    tend to develop lower leg strength unless they train for it.

•   Girls tend to land with a straighter knee than boys. This reduces the effectiveness of their muscles as shock
    absorbers.

•   Girls tend to let their knees drop inward during cutting/pivoting/landing maneuvers, which can put larger stresses
    on the ACL.

•   Girls often have more strength in their quadriceps muscles than their hamstring muscles. This puts more stress
    on the ACL.

Can ACL tears be prevented?

Despite relative success of surgeries to repair the torn ACL, it is clear that it is equally important to devise strategies to prevent this serious injury.

In 2013, the Sports Medicine Division opened The Micheli Center for Sports Injury Prevention based at the Boston Children’s Hospital satellite in Waltham. Each child receives a comprehensive assessment to determine child and sport-specific risk factors for injury, including ACL injury. The child and family are given a series of recommendations to help prevent injury in sports training and competition.

In general, athletes and active young people can reduce their risk by:

•   maintaining general health and fitness: sport-specific conditioning, diet, exercise, sleep
•   learning/using proper sport-specific movements and techniques
•   wearing/using proper sport-specific gear
•   learning which moves cause risks (risk awareness)
•   strengthening hamstring/leg (especially for girls)

To learn more about ACL injury prevention, please visit The Micheli Center for Sports Injury Prevention and download Boston Children’s ACL Injury Prevention Guide. To learn more about female athletes and ACL injuries, please download Boston Children’s Female Athlete ACL Guide.

Why have ACL tears become more common?

There are several factors behind the apparent increase in ACL injuries, including:

•   Children are playing sports at a more competitive level at younger ages and are more likely to focus on a single
    sport. Both factors may increase risk for ACL tears.
•   Children are maturing earlier. They are bigger, stronger and faster, which means greater risk for adult-like injuries like
    ACL tears.
•   Doctors are more aware of the injury and have become more adept at recognizing it.
•   Newer technologies like MRI and arthroscopy help doctors better visualize the injury.

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- Sandra L. Fenwick, President and CEO

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