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ACL Injuries

What is an ACL injury?

ACL stands for anterior cruciate ligament, 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 or bend them 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.

A child’s ACL tear is more difficult to treat than an adult’s because of the need to avoid injury to the bones’ growth plates above and below the knee.

How do you evaluate an ACL injury?

If your child’s knee suddenly swells after an accident or injury, she may have a torn ACL or another serious knee problem.

To help protect your child from more injuries that could hurt her growing bones and joints, it is important to get a thorough evaluation and proper treatment.

When you and your child come to our clinic, we will ask what happened before her knee began to swell and hurt. Next, we will examine your child’s knee. To doctors trained in sports medicine, knees with ACL tears often feel loose.

We cannot be sure that your child has a torn ACL until the swelling in her knee has gone down, which takes about seven to 10 days. We will probably take radiographs of your child’s knee to get more information on what is wrong.

If it is not clear that the ACL is torn or if we think your child may have other injuries, we may ask your child to have an MRI.

Who gets ACL injuries?

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.

What is your experience with ACL injuries?

At Children’s Hospital, 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 her knee.

How do you treat ACL injuries?

Transepiphyseal anterior cruciate ligament reconstruction.
Transepiphyseal anterior cruciate ligament reconstruction.

No matter your age, treating an ACL injury with methods that do not require surgery is desirable. This is especially true with growing children and teenagers.

One of the most important ways to prevent repeat injuries is to modify activities that might injure the knee as it heals, such as high-level athletics that require jumping, pivoting, contact with other players or playing on an uneven surface.

If your child’s injury is more severe or if physical therapy does not make her knee stable enough to return to sports, she may need surgery.

We have a new sports physical therapy facility to help your child recover.

Non-surgical treatments for ACL injuries

If your child’s injury is mild, she may be able to recover with the help of physical therapy alone. Our staff is expert at devising and teaching exercises that help bring back motion in your child’s knee and strengthen the muscles around it.

We have a sports lab on site to help our patients with rehabilitation.

Surgery for ACL injuries

The goal of surgery in young patients is to make their knee stable with the least possible risk of affecting their growth.

During surgery, we use tissue taken from your child’s hamstring tendons to reconstruct her ACL. We drill small holes in the shinbone and the thighbone. Then, we pass the new ligament through the drill holes and secure it to the bones. This surgery requires only small incisions.

During the operation, the doctor inserts a tool called an arthroscope into your child’s knee and uses pictures displayed on a large monitor to guide his actions.

After surgery, your child will have regular physical therapy, most likely twice a week for four to eight weeks. This will help strengthen her muscles and stabilize her knee. She probably will need physical therapy for nine months to a year after surgery.

Read more about surgery for anterior cruciate ligament deficiency in children and young adults.