Knee injuries in children are rising as kids become more involved in high-level athletics, and the complexity of these injuries has increased as well. Anterior cruciate ligament (ACL) tears have become more and more common in the pediatric population. Because children are not simply “small adults,” the treatment of these injuries requires the expertise of a pediatric orthopedic surgeon who specializes in knee injuries.
School’s back in and so are after-school sports. Although football tends to be the biggest culprit amongst boys, we also see significant injuries that occur in both boys and girls who participate in soccer, basketball, dance, gymnastics and parkour. Twisting and cutting on a planted foot are the most common causes of injury.
Evaluation and Imaging
If your child sustains a significant injury to his or her knee, an initial evaluation in the emergency room or pediatrician’s office will likely reveal a painful, swollen knee with associated range of motion restriction. The doctor may note tenderness and laxity (the looseness of a limb or muscle) upon exam and will likely order X-rays and possibly an MRI scan as well.
X-rays are very important in the initial evaluation of a knee injury in order to rule out a fracture, but also to assess a child’s growth plates. The patency (openness) of the growth plates plays an important role in determining the most appropriate treatment method.
MRI is a specialized imaging tool that allows evaluation of all of the soft tissues in and around the knee, including the cartilage, meniscus, ligaments, tendons, nerves, and blood vessels. An MRI is nearly essential in the work-up of ACL injuries since there’s a possibility other structures around the knee are injured as well.
The meniscus, which is specialized cartilage in the knee that provides cushion and stability, is often torn as well in the case of ACL injuries. Other ligaments, such as the collateral ligaments on the sides of the knee (MCL and LCL), or the posterior cruciate ligament can also be torn in severe ACL injuries. All of these structures and potential injuries can be evaluated by MRI.
Although non-operative treatment deserves consideration in all cases, surgery is usually required for ACL tears. When treating non-operatively, the risk of further injury to the knee with return to activities generally outweighs the risks of surgical treatment. However, surgical treatment is not emergent, and proper evaluation of the injury as well as discussion about the treatment and rehabilitation are essential for the best outcome.
The surgery that is usually performed for ACL tears is an arthroscopic ACL reconstruction. The ligament is reconstructed rather than repaired because repairs have previously been shown to fail too often. This procedure is performed under general anesthesia, usually with an additional nerve block to aid in pain control.
The procedure starts with an arthroscopy, when the surgeon confirms the MRI findings and repairs any meniscal tears. Then, the torn ACL is removed. Next, the surgeon will harvest a graft – which means he or she will take a piece of healthy tendon from another part of a patient’s body to replace a tendon that’s been removed. Grafts taken from the patient’s own knee generally lead to better success rates in children than cadaver grafts, which are taken from a person who has passed away. Surgeons will generally use hamstring, patella, or quadriceps tendons for grafts, depending on their preference.
After harvesting the graft, tunnels are drilled in the bone above and below the knee joint, and the graft is placed through the tunnels and secured to the bone. If the patient’s growth plates have closed (usually after 14 for girls and 16 for boys), then the tunnels are drilled in the standard orientation that is performed for adults. If the patient’s growth plates are still open, a modification to the tunnel placement is performed in order to avoid damage to the growth plates.
A child will wear a knee brace and use crutches for a period of 4-6 weeks following surgery. Children are initially prescribed pain medication for pain control, transitioning to over-the-counter anti-inflammatory medication after the first or second week. Most children stay home from school for about a week or two for recovery. After surgery, patients will follow-up with their surgeon on regular intervals for check-ups over the next year or so.
Children typically begin physical therapy about a week after surgery. The goals of therapy are initially to regain range of motion and strength, and then to work toward walking without crutches. Exercises are modified over time to allow a child to slowly return to his or her normal activities.
Return to Activities
A child is usually able to return to his or her chosen activities - football, soccer, dance, etc. - between 9 and 12 months after surgery. The decision to allow a child to return is based on evaluation by both the surgeon and the physical therapist.
ACL injuries are common among young athletes, and it’s not possible to guarantee that any form of preparation will completely eliminate your child’s chance of having one. However, ACL injury prevention programs have been shown to be effective. Neuromuscular training is aimed at landing on slightly flexed knees without the knee buckling inward, as well as increasing the hamstring to quadriceps strength ratio. Proper falling is also important, especially for skiers. These protocols are usually implemented by a physical therapist or athletic trainer, and work best if they are started at least six weeks prior to an athletic season.