Children's Hospital Colorado

Anterior Cruciate Ligament (ACL) Injury

What is the anterior cruciate ligament (ACL), and where is it located?

The anterior cruciate ligament (ACL) is a commonly injured ligament in the knee. Ligaments are tough bands of tissue that connect the ends of bones together.

The ACL is located in the center of the knee joint, where it runs from the backside of the femur (thigh bone) to connect to the front of the tibia (shin bone). It has two main functions:

  • To prevent the tibia from sliding forward on the femur
  • To prevent the tibia and femur from rotating out of position during various sports movements, such as cutting, twisting and landing activities

What is an ACL tear?

The ACL plays an especially important role when performing activities that require quickly changing direction, such as soccer, football and basketball. If the knee receives too much stress, the ACL could be strained or completely torn.

Athletes who tear 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.

Orthopedic doctors at the Orthopedics Institute 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.

Are girls more likely to tear their ACL than boys?

Anyone can suffer an ACL injury; however, proper training can help athletes 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.

Have ACL tears become more common?

Research has shown that about one in every 60 young athletes will experience an ACL tear at some point during their athletic career. Unfortunately, these numbers are increasing due to the increased intensity of sports.

What causes an ACL tear?

Impact to the outside of the knee or sudden changes in direction can stretch, fray or tear the ACL completely. Too much strain on the knee joint from sharp pivots or quick stops can also injure the ACL. An ACL injury can also occur without any contact.

Can ACL tears be prevented?

Prevention starts with understanding the importance of balancing the strength of the muscles around your knee and core. The ACL is at highest risk when the hamstrings do not fire with enough force or at the right timing to protect the ACL. Good muscle strength and coordination minimizes injuries – this includes strength in your hamstrings, quadriceps and your core (abdominal and gluteal muscles).

The Connection Journey
Healing the whole athlete

Carolyn tore her ACL last year but is back on the field and sharing her journey with Erin who is about to have ACL surgery. Here, we know that ACL injury recovery is different for every athlete, but it helps to hear from someone who has been there and got back on the field.

Watch their stories

Contact the Orthopedics department

Cartoon image of a patient and doctor having a telehealth call.

Keeping you safe, wherever you are

We're here when you need us with the same safe, high-quality care we've always offered, even during the pandemic. Now, in many cases, you can get that care without even leaving home because we offer virtual visits across every one of our specialties.

See if telehealth is right for your child


Get to know our pediatric experts.

Caitlin Dierkes, PA-C

Caitlin Dierkes, PA-C

Physician Assistant

Stephanie Sharp, PhD

Stephanie Sharp, PhD

Patient ratings and reviews are not available Why?

Brian Shaw, MD

Brian Shaw, MD

Orthopaedic Surgery

Emily Sweeney, MD

Emily Sweeney, MD

Pediatrics, Sports Medicine