Anterior Cruciate Ligament Tears (Pediatric)

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What are anterior cruciate ligament tears?

The anterior cruciate ligament (ACL) is one of four major ligaments in the knee. There are two collateral ligaments on the side and two cruciate ligaments which cross in the middle. Your child’s ACL is a strong ligament that allows the knee to remain stable while cutting and pivoting during sports.

An ACL tear was once an injury exclusive to high level athletes. However, with the large increase in youth and adolescent sports we are seeing a large rise in ACL tears in these age groups.

What causes anterior cruciate ligament tears?

Mechanism of injury can either be from a direct blow to the side of the knee (getting tackled from the side in football for example) or non-contact injury which occurs when you are running or jumping, and then you suddenly stop, change direction and twist.

Other structures in the knee can be injured when a patient tears the ACL such as the meniscus, articular cartilage, and other major ligaments.

Who is affected by anterior cruciate ligament tears?

Risk factors for tearing the ACL are being female (relates to the way females use their muscles compared to males), increased looseness of the ligaments and hamstring muscles, and weakness of core muscles.

ACL tears by the numbers are:

  • There are over 250,000 ACL Injuries each year in the United States.
  • Because adolescents and children are high activity groups, their knees are continually at risk. They have a 15-20 percent chance of injuring their ACL again.
  • Girls are five times more likely to tear their ACL than boys.
  • Girls have up to a 20-25 percent chance of re-tearing their reconstructed ACL.

What are the symptoms of anterior cruciate ligament tears?

In many cases, children feel their knee give out, many times with an audible “pop.” When this occurs, they are usually unable to continue with sports and other activities, and the knee becomes more swollen and painful in the ensuing hours. Walking for the next few days may require crutches because of difficulty bending and straightening the knee.

How are anterior cruciate ligament tears diagnosed?

Physical Examination: This test is important in evaluating for an ACL tear. Children and teens cannot always express what is bothering them. They cannot always answer medical questions and be patient and helpful during a medical examination. The pediatric and adolescent sports medicine specialists at our Center know how to examine and treat your child in a way that allows them to be relaxed and cooperative.

Lachman Test: As in almost all acute injuries, loss of motion and instability is an important finding. The Lachman Test is performed with the knee bent 30 degrees. The physician gently pulls on the tibia to check the motion of the forward leg in relation to the lower leg. Under normal conditions, the patient’s knee will have less than three mm of forward motion, with a firm stopping felt when no further movement is observed. However, a patient with a torn ACL will have significantly greater forward motion and a soft end feel at the end of the movement. Because the ACL is torn, the patient will experience loss of restraint of the forward movement of the tibia. The same test is performed with the knee flexed to 90 degrees; this is called the anterior drawer test.

Pivot Shift Test: Our doctors perform this test to determine the amount of rotational instability present with the ACL tear.

Another essential component in the successful treatment of ACL tears in the pediatric and adolescent athlete is appropriate assessment of their maturity. There is often a disconnect between chronological and skeletal age. Knowledge of the skeletal age of your child aids the surgeon in his surgical planning to determine how respectful to be of the remaining growth plates in the knee. We use hand and knee x-rays and menarchal status of our female athletes to get the best assessment of the patients true bone age.

Diagnostic Imaging: Magnetic Resonance Imaging (MRI) helps the physician obtain an excellent image of all parts of the knee. The MRI is not an absolute indicator for a torn ACL, however, it can document damage to the meniscus. The meniscus is composed of cartilage inside the knee, which provides cushioning and is frequently torn at the same time as an ACL tears during injury.

What is the treatment for anterior cruciate ligament tears?

Post-Injury Treatment

Patients should ice the injury to prevent inflammation and compress areas around the knee to control swelling. Elevation is also key in controlling and reducing swelling. Rehabilitation knee braces are often used early after the injury as well as for postoperative care. The brace plays an important role in putting the joint at rest and protecting it while still allowing appropriate but limited motion.


A rehabilitation program is designed to restore the patient’s range of motion and muscle strength. They will also be instructed on how to use crutches appropriately. Weight-bearing exercises can only be pursued after the swelling around the knee decreases. Increasing the range of motion of the knees is important in preventing stiffness and muscles tightness.

Surgical Treatment

Surgical treatment for a torn ACL is not always necessary. Although surgical intervention often leads to complete success, not everyone needs the ligament to return to his or her pre-injury level of function. If the patient is not incredibly physically active, reconstruction is not necessary. Also, ACL reconstruction requires that the patient undergo many months of rehabilitation. This involves both time and commitment and should be strongly considered when making a decision.

Surgical treatments are:

  • ACL Reconstruction: The ACL has little to no capacity to heal on its own. Therefore it cannot simply be sewn back together; it must be reconstructed. This involves substitution of a new ligament for the damaged one.
  • Skeletal Immaturity: Many young patients who injure their ACL are still growing; this requires special consideration. The standard technique of ACL reconstruction requires drilling tunnels in the tibia and femur bones that would cross the normal growth plate (physis) of an actively growing child. Therefore, the ACL reconstruction technique requires modifications that avoid injury to the growth plate. The specialists at our center use physis sparing and respecting techniques to avoid growth disturbances.
  • Graft Choice: Autograft is when surgeons take tissue from somewhere else in the patient’s own body to reconstruct the ACL. Choices for autografts are the hamstrings, patellar tendon, and quadriceps tendon. Surgeons can also use an allograft to help reconstruct or augment autograft tissue for ACL reconstruction. This type of graft is harvested from a cadaver and is advantageous for a few reasons. First, the operation takes less time because the harvesting time is removed. Also, the patient’s own tissue is not disturbed, therefore leading to a less invasive procedure and less scaring, and easier early recovery.

Surgical Procedure

Reconstruction of an isolated ACL tear takes between 1-2 hours. A patient may undergo general anesthesia, spinal anesthesia or local anesthetic with sedation. Once the patient is anesthetized, the surgeon will begin the arthroscopic procedure. An arthroscope, is a thin microscope that is about the size and shape of a straw. At the end of the arthroscope, there is a miniature video camera and lens that can magnify the image it sees to about 25 to 30 times the original size. This image is sent up to a video screen where the surgeon and his or her team can get a clear and detailed view of the inside of the knee. With the arthroscope and small, specialized instruments, the surgeon can reconstruct the ligaments, avoiding large incisions and trauma to surrounding tissues. Before the surgeon begins reconstruction, he or she uses the arthroscope to map out the area being worked on. This allows the surgeon to identify key knee structures and also view any additional damage.


Following surgery, the patient receives:

  • Written discharge instruction
  • Copies of surgical pictures
  • Physical therapy prescription
  • Outline of physical therapy guidelines and return to sport

Pain Medication

Because of the minimally invasive nature of the current ACL reconstructions technique, isolated ACL surgery is usually an outpatient procedure. Although crutches are given to the patient to assist in necessary mobility, it is essential that the patient rest and elevate the leg, especially in the first few days. This minimizes swelling and helps the body to reestablish all pre-surgical functioning.

Physical Therapy and Rehabilitation

Rehabilitation is essential to a successful recovery and begins soon after surgery. The ultimate goal in rehabilitation is to return to a condition where the knee provides dynamic stability, while still maintaining a full range of motion. Therefore, recovery progress is judged by the patient’s perception of how stable the knee feels. Often, a surgeon will prescribe a brace for the patient to be used during the rehabilitation period. The rehabilitation brace is adjustable; it can be locked in a straight position or set to allow a certain amount of motion. The brace is normally taken off while the patient is exercising. Usually, a therapy program will begin with range-of-motion and resistive exercises. Then, when the patient is able, exercise incorporating power, flexibility, endurance and coordination is added. Lastly, the patients will develop speed and agility through sport specific exercises. Most patients begin light activity, such as biking or rowing, about 4-6 weeks after surgery. Running starts at 3 months and competitive activity is delayed until 6-9 months after surgery.

The good news is that the success of ACL reconstruction is typically quoted around 90%. Certain subsets of patients are at higher risk to re-tear the grafts (such as young female soccer players). Our plan will be to have your athlete back on the field in 6-9 months post-operatively.


There are some complications that can occur as a result of surgery to reconstruct the ACL:

  • Infection (1 percent)
  • Blood clots
  • Failure of the graft/re-rupture (3-10 percent)
  • Need for re-operation
  • Knee stiffness (arthrofibrosis)