Are ACL Tears Common in Adolescent Athletes?

Anterior cruciate ligament tears are fairly common in adolescent athletes. Amongst youth female soccer players, as many as one in three athletes will have experienced some degree of injury to their ACL by the time they conclude their soccer career. Activities such as skiing, football, and basketball, which involve pivoting and sudden decelerations, pose a higher risk of ACL tears.

The adolescent athlete’s body is growing and developing. There is commonly muscle imbalances during this rapid period of growth as well as a lack of muscle endurance. Young athletes, particularly female athletes, also tend to be knock kneed (in valgus). Adolescent athletes are also more often playing competitive, organized sports year-round. All of these factors predispose young athletes to ACL tears. However, there are interventions that can reduce the incidence of ACL tears in our young athletes such as improving landing and deceleration mechanics, strengthening one’s gluteal and hamstring musculature which tends to be overpowered by one’s quadriceps and hip flexor musculature, not over training, and utilizing stable shoe wear and equipment.

Symptoms of an ACL Tear in Children

An anterior cruciate ligament tear in adolescent athletes is usually not from contact or a collision with another player. More often, a young athlete tears their ACL when they suddenly decelerate, change directions, or land a jump incorrectly.

One’s ACL can tear when the femur (thigh bone) forcefully slides posteriorly and rotates externally in relationship to the tibia (shin bone). Athletes typically feel a pop in the knee and experience sudden pain and swelling. Athletes who try to walk on the injured knee may feel that their knee “buckles” and feels unstable. It is difficult for people with a freshly torn ACL to comfortably bear weight on the knee. In the first 24-48 hours the knee swells, and it becomes more difficult to bend and fully straighten the knee. The symptoms of an ACL can vary, but may include:

• Popping sound at the time of injury
• Swelling and tenderness
• The sensation of the knee being loose
• Instability of the joint
• A decrease in knee range of motion
• Immediate and slowly increasing pain

It is rare for youth athletes to be able to continue playing after sustaining an acute ACL tear. However, if an athlete rests the knee, the knee can feel quite normal with everyday activities within several weeks with there being minimal swelling and a return of normal knee range of motion. However, if a young athlete then returns to cutting and pivoting sports, they will most likely experience another forceful giving way episode of the knee. This may do additional damage to the knee, such as tear one’s meniscus.

Should Adolescent Athletes get ACL Surgery?

Historically, knee surgeons would recommend against ACL surgery in skeletally immature child who tore their ACL. However, it was found that these young athletes would return to cutting and pivoting sports as their knee felt better. They would then have recurrent instability episodes to the knee. These additional giving way episodes would inevitably cause further damage to the knee. Oftentimes, the medial meniscus would tear. Without a normal medial meniscus, there would be increased stress and shear forces on the coating (articular) cartilage in the knee which would then wear resulting in arthritis. As such, knee surgeons were seeing kids that tore their ACL in their early teens developing arthritis and by the time they were in their late teens. This accelerated arthritis led to knee surgeons recommending ACL surgery after a child tore their ACL in order to restore stability to the knee, allow the child to get back to sports with a stable knee, and also prevent further damage and early arthritis to their knees.

The technique used to fix one’s torn ACL depends on an adolescent athlete’s physiologic age (not necessarily their chronologic age) and degree of skeletal maturity. Most girls who are 14 or older and most boys who are 16 or older have reached skeletal maturity or are close enough to skeletal maturity that they can be treated like an adult with an ACL tear with a 95% chance of an excellent outcome. However, in girls and boys younger than this, a knee surgeon needs to assess the child’s bone age and determine how much growth they have remaining. If one still has one year or more of growth remaining, then the ACL surgical technique typically needs to account for and protect the child’s physes (growth plates) from injury during the surgery. Otherwise, an ACL surgery may damage the physis and cause premature arrest of a physis leading to a limb length inequality or an angular growth deformity of the leg.

There are several ACL surgical techniques that may be employed in a young athlete who has substantial growth remaining. These include repairing the torn ACL and not reconstructing it, or doing a physeal sparing ACL reconstruction where a graft is placed within the knee without drilling and creating bone tunnels across the femoral and tibial physes. The patient, parent, and surgeon will work closely to determine the best course of surgical treatment to repair or reconstruct a torn ACL in a young athlete.

Anterior Cruciate Ligament Reconstruction Using Quadriceps Tendon Autograft in Adolescent Athletes

For young athletes who require ACL reconstruction surgery, Dr. Cunningham recommends utilizing an autograft (a portion of one’s own tendon) over an allograft (a piece of donor tendon). Allograft ACL’s tend to re-tear at a much higher rate, particularly in young athletes. As for autografts, there are 3 main tendon graft options: hamstring, patellar tendon, or quadricep tendon. There are advantages and disadvantages to these different grafts (please see the other articles on this website regarding this). However, anterior cruciate ligament reconstruction with quadriceps tendon autograft is very successful in adolescent athletes who have torn their ACL. Advantages of a quadriceps tendon graft include:

• Thickest, strongest graft option
• Ability to return to high demand activities
• Lower reinjury rate compared to a hamstring graft
• Lower rate of kneeling pain after surgery compared to a patellar tendon graft
• Lower rates of knee arthritis compared to a patellar tendon graft

Can you still Grow After ACL Surgery?

During ACL reconstruction in an adult, a drill hole is made in the bottom end of the femur and another drill hole is made in the top end of the tibia. The graft is then anchored into these drill holes. In adults, these drill holes cross the old “closed” growth plate in both the femur and tibia. In a child who has growth remaining, a surgeon has to be considerate of how much growth remains and not drill across these “open” active growth plates as they would in an adult. Drilling across an open growth plate in order to create a bone socket for an ACL graft can injure a growth plate and cause it to close and stop growing prematurely. This can lead to the leg growing less than it would have, thus causing a limb length difference. In older children, who have little growth remaining, the growth plate can be safely drilled across as the growth plate is nearly closed and will no longer contribute significantly to one’s growth.

Instead of risking injury to a growth plate by drilling across a child’s growth plate, Dr. Cunningham one of a handful of surgeons who does primary ACL repair surgery. In ACL repair surgery, the torn ACL is directly reattached to the femur bone from which it can tear away from. In this technique, Dr. Cunningham is able to save one’s original ACL instead of replacing it with a tendon graft. This ACL repair technique also does not put the growth plate at risk as there is no tunnel drilling required.

However, if an ACL tears in the middle of the ligament, this type of ACL tear is not a candidate for ACL repair surgery. In this case, the ACL must be reconstructed with an ACL graft. Fortunately, there are ACL surgical reconstruction techniques utilized in children that do not require drilling across the growth plates. As long as the surgeon does not drill across the growth plate in a younger child, the child will have normal growth of their lower extremity.

What is the Recovery Like After ACL Surgery in Children?

The anesthesiologist will place a femoral nerve block prior to surgery and then administer a light general anesthetic in the operating room. Dr. Cunningham does all ACL surgery arthroscopically, and patients go home the same day. The knee is iced and elevated for the first few days. A knee brace is applied after surgery to hold the knee straight while walking, allowing patients to start weight bearing as tolerated right away. Physical therapy is started the day after surgery. This initially consists of easy range of motion exercises. The knee brace can be discontinued when there is adequate quadriceps function, which normally takes 2 weeks. By 2 weeks from surgery, patients are off of the crutches and out of the knee brace (unless there is also a meniscus repair performed). Patients can spin on a bike with no resistance directly after surgery. By 8 weeks from surgery, patients can be riding a bike outdoors. By 4 months from surgery, patients can start jogging, playing golf, and doing light hiking. Patients who have had ACL repair surgery can be back to all sports and activities by 5 months. However, patients who require ACL reconstruction surgery cannot get back to cutting and pivoting sports like football, skiing, and soccer until 8-10 months or until their strength in the affected leg is at least 90% of their normal side and they pass a specific Sports Test with their physical therapist. Once cleared to return to all sports, patients are asked to wear a sports knee brace for one year from the time they are cleared to return to all sports.

Dr. Cunningham checks his patients in the office at regular intervals after surgery to be sure they are hitting all the appropriate milestones. In Dr. Cunningham’s experience, his patients that have had ACL surgery and who diligently perform the appropriate rehabilitation can get back to all their sports at the same level and be no more likely to injure their reconstructed ACL compared to injuring their other ACL.

Dr. Cunningham checks his patients in the office at regular intervals after surgery to be sure they are hitting all the appropriate milestones. In Dr. Cunningham’s experience, his patients that have had ACL surgery and who diligently perform the appropriate rehabilitation can get back to all their sports at the same level and be no more likely to injure their reconstructed ACL compared to injuring their other ACL.