Bone, Joint and Muscle Conditions

ACL Injuries

What Is an ACL Injury?

ACL injuries are damage to the anterior cruciate ligament (ACL) in the knee. The ACL is one of four ligaments that keep the knee from wobbling or giving out when you move. To understand ACL injury, it helps to know a little about how the knee works.

The knee is a large joint where the shinbone (tibia) meets the thighbone (femur). Two ligaments run along either side of the knee. The medial collateral ligament (MCL) is on the inside and keeps the knee from bending in. The lateral collateral ligament (LCL) is on the outside and keeps the knee from bending out.

Two other ligaments - the ACL and the posterior cruciate ligament (PCL) - cross each other in the middle of the knee. They work together to keep the shinbone attached to the thighbone.

The ACL connects the front part of the shinbone to the back part of the thighbone so that the shinbone does not slide in front of the thighbone.

When the knee is forced into an unusual position, the ACL and other ligaments can tear, partially or all the way. ACL tears occur when children:

  • Stop or change direction suddenly
  • Twist their knees
  • Bend their knees sideways

This can happen during accidents while skiing, bicycling or riding in a car. It also can happen during sports that require a lot of jumping, pivoting and quick stops and starts, such as basketball, volleyball and soccer. Children sometimes also tear their ACL when they stumble or fall, or when they run into others while playing sports.

ACL Injuries in Children

A child's ACL tear is more difficult to treat than an adult's. This is because doctors must avoid injury to the growth plates on children's bones above and below the knee.

Injuries to the ACL are becoming more common in growing athletes. Researchers think this may be due to three main reasons:

  1. More children are involved in sports.
  2. Doctors are more likely to recognize knee injuries in children.
  3. We are getting better at identifying injuries to the ligaments.

Teenage girls are two to eight times more likely to injure their ACL than are boys of the same age. We do not know exactly why this is so, but it may have to do with anatomy, muscle strength, coordination and hormonal differences.

Older children have more ACL injuries than younger children. Until about age 12, children are more likely to break the bone where the ligament attaches.

ACL Injuries at Seattle Children's

At Seattle Children's, we are experts at treating growing athletes. We have a team of doctors, physician assistants and physical therapists that treats these injuries.

We perform surgery to reconstruct torn ACLs in young athletes whose knees either do not respond to physical therapy or are too wobbly to allow them to return to sports.

Our surgical methods limit the risks of injury to growth plates on the bone. This increases the chances that your child will be able to return to sports, usually in nine to 12 months after surgery.

Our rehabilitation program includes regular physical therapy designed so that your child will recover range of motion, rebuild strength and stability, restore balance and regain confidence in using the knee.