Pediatric Knee Injuries - ACL

Knee ligaments are the short bands of tough, flexible connective tissue that hold the knee together. Knee ligament injuries can be caused by trauma, such as a car accident. Or they can be caused by sports injuries. An example is a twisting knee injury in basketball or skiing.

The knee has four major ligaments. Ligaments connect bones to each other. They give the joint stability and strength. The four knee ligaments connect the thighbone (femur) to the shin bone (tibia). They are:

• Anterior cruciate ligament (ACL). This ligament is in the center of the knee. It controls rotation and forward movement of the shin bone.
• Posterior cruciate ligament (PCL). This ligament is in the back of the knee. It controls backward movement of the shin bone.
• Medial collateral ligament (MCL). This ligament gives stability to the inner knee.
• Lateral collateral ligament (LCL). This ligament gives stability to the outer knee.

Cruciate ligaments

The ACL is one of the most common ligaments to be injured. The ACL is often stretched or torn during a sudden twisting motion. This is when the feet stay planted one way, but the knees turn the other way. Slowing down while running or landing from a jump incorrectly can cause ACL injuries. Skiing, basketball, and football are sports that have a higher risk for ACL injuries.

The PCL is also a common ligament to become injured in the knee. But a PCL injury often occurs with a sudden, direct hit, such as in a car accident or during a football tackle.

Collateral ligaments

The MCL is injured more often than the LCL. Stretch and tear injuries to the collateral ligaments are often caused by a blow to the outer side of the knee. This can happen when playing hockey or football.

Your healthcare provider will ask about your health history and do a physical exam. You may also need one or both of these tests:

• X-ray. This imaging test can rule out an injury to bone instead of a ligament injury. It uses energy beams to make images of internal tissues, bones, and organs on film.
• MRI. This test uses large magnets, radio waves, and a computer to make detailed images of organs and structures in the body. It can often find damage or disease in bones and a surrounding ligament, tendon or muscle.

Treatment will depend on your symptoms, age and general health. It will also depend on how severe the condition is. Treatment may include:

• Pain medicine, such as ibuprofen
• Muscle-strengthening exercises
• Protective knee brace
• Ice pack to ease swelling
• Surgery

Children who play basketball, volleyball, soccer or football or who ski are most likely to injure their anterior cruciate ligaments (ACL) when they slow down, pivot or land after a jump.

If your child injures his, he may not feel any pain immediately. Your child might hear a popping noise and feel his knee give out from under him.

Within a few hours, your child will notice swelling at the knee. The knee will often hurt when attempting to stand on it. It's important to keep weight off the knee until your child can see your healthcare provider, or he may injure the knee cartilage. Your child should use an ice pack to reduce swelling and keep the leg elevated. If needed, use a pain reliever. If your child must walk, use crutches and be sure to see a doctor right away to have your knee evaluated.

The knee is a joint where three main bones join: the femur, or thigh bone; the tibia, or shin bone; and the patella, or knee cap. Several ligaments attach to the femur and tibia and give the joint strength and stability. One of these, the ACL, is in the center of the knee and limits rotation and the forward movement of the tibia.

The ACL is most often stretched or torn by a sudden twisting motion — when, for example, the feet are planted one way and the knees are turned another. A child can also injure the ACL by quickly changing the direction in which they are moving; by putting the brakes on too quickly when running; or, when landing from a jump. A woman's body structure and hormones cause more force on the ligaments, increasing the likelihood of injury during sports and athletic activities.

Many ACL injuries can be prevented if the muscles that surround the knees are strong and flexible.

Prevention focuses on proper nerve and muscle control of the knee. Exercises aim to increase muscle power, balance and improve core strength and stability.

The following training tips can reduce the risk of an ACL injury:

• Train and condition year round.
• Practice proper landing technique after jumps. This involves bending your knees to absorb the force and keeping them in line with your feet.
• When you pivot, crouch and bend at the knees and hips. This reduces stress on the ACL.
• Strengthen your hamstring and quadriceps muscles. The hamstring muscle is at the back of the thigh; the quadriceps muscle is at the front. The muscles work together to bend or straighten the leg. Strengthening both muscles can better protect the leg against knee injuries.

Your child's doctor may conduct physical tests and take X-rays and obtain an MRI to determine the extent of your ACL damage. If the ACL is only partially torn, your doctor may prescribe an exercise program to strengthen surrounding muscles and a brace to protect the knee during activity. Your child may or may not need surgery. Surgery can be performed to reconstruct the torn ligament from a piece (graft) of strong, healthy tissue taken from another area near the knee (autograft) or from a cadaver (allograft). If the ACL is completely torn, it may need to be replaced surgically.

Successful surgery tightens your knee and restores its stability, which helps to avoid further injury.

After ACL reconstruction, your child will need to do rehabilitation exercises to gradually return your knee to full range of motion and stability.

You also may need a knee brace temporarily and will probably have to stay out of sports for about six months to a year after the surgery.