Children's Hospital Colorado

Anterior Cruciate Ligament (ACL) Injury

What is an anterior cruciate ligament (ACL) injury?

The anterior cruciate ligament (ACL) is a commonly injured ligament in the knee. The ACL works to stabilize the knee and plays an especially important role when performing activities which require quickly changing direction, such as soccer, football and basketball.

Athletes who have torn their ACL sometimes report a sensation of their knee “giving out." Short term, this makes it difficult to play sports. Long term, it is believed that this “giving out” causes damage to other structures in the knee, including the cartilage, which can cause arthritis. Doctors at Children’s Hospital Colorado believe that surgical reconstruction is the best treatment for long-term preservation of the knee and for young athletes to make an early return to sports. See what an injury to the ACL looks like.

Who is at risk to injure their ACL?

Anyone can suffer an ACL injury; however, proper training can help athlete minimize their risk. Females are approximately six times more likely to tear their ACL than males due to reasons ranging from differences in bone structure to muscle imbalances.

Some research shows that females who participate in training programs to help strengthen specific muscles may decrease their risk of ACL injury. Children's Hospital Colorado offers the Sportsmetrics Program, which helps young athletes avoid injuries. Learn more about how we help teens prevent sports injuries.

Helpful resources for ACL injury:

What are signs and symptoms of an ACL injury?

Many anterior cruciate ligament (ACL) injuries happen while playing sports, but not necessarily from a hard collision. In fact, most ACL injuries are what we call “non-contact,” meaning they occur during a sudden change in direction, not when struck by another player.

Athletes who have suffered an ACL injury typically experience rapid swelling of the knee within 24 hours of the injury. Some may be able to walk after the injury, or even continue to play their sport. Many people report that they hear or feel a “pop” in their knee when the injury occurs. As the swelling subsides over the following days or weeks, most people notice that their knee feels unstable or “gives out.”

How will my child’s doctor diagnose an ACL injury?

ACL injuries are diagnosed by a physical examination to assess the stability of the knee. X-rays are important to distinguish between a torn ACL or a fracture, as they can have similar symptoms. Magnetic resource imaging (MRI) is also helpful because it is able to check for damage to other ligaments and cartilage in the knee.

Learn more about knee x-rays and other common orthopedic tests.

How is an anterior cruciate ligament (ACL) injury treated?

Although non-surgical treatment – such as knee-bracing and physical therapy – is an option, it is generally not the treatment of choice for young people. Young people who choose not to undergo surgical reconstruction tend to experience continued episodes of their knee “giving out” and long-term knee problems.

In general, doctors at Children’s Hospital Colorado recommend a knee operation to make a new ACL out of another tendon. There are several different choices for the new ACL, which your child’s surgeon will discuss with you.

An important consideration for ACL surgery in children and adolescents is that their bones are still growing. Bone growth comes from the growth plates, which are at the ends of the bones and increase the length of the bone. Traditional ACL surgery puts these structures at risk for causing a limb length discrepancy or a deformity. At Children's Hospital Colorado, we specialize in surgical techniques to minimize this risk and maximize a young athlete’s return to competitive sports and recreation.

Learn more about our Sports Medicine Center that treats ACL injuries.


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