By Dr. Eric W. Edmonds
Children often tend to fracture before tearing the anterior cruciate ligament (ACL). However, occasionally it is a pure soft-tissue injury.
I have seen isolated ACL tears in 5-year-olds, but this is a very rare age to sustain this injury. The slightly older 7- to 9-year-old group seems to suffer the injury with greater frequency. Both boys and girls seem at risk. Although an ACL may be torn during any activity, the most common causes in this age group seem to be related to gymnastics, trampoline, bicycle and football activities.
A torn ACL has an indirect effect on the knee. If the cartilage is injured, friction increases and the cartilage surface wears down, resulting in arthritis. Recent studies have shown that ACL-deficient knees have an increased rate of tears in the meniscus, cushions that protect the knee’s cartilage. Tears can result in increased damage to cartilage and long-term issues with arthritis.
Historically, children were treated with activity modification and braces for a decade until they could have their ACL reconstructed. Recent research has demonstrated a fivefold increase in meniscus tears in children just by waiting six months for surgery. This may result in a serious long-term consequence for these children.
Over the last few decades, a few surgical techniques and advances in technology have allowed for ACL reconstruction in children with open growth plates. Some require X-rays during surgery, but all have found a way to bypass violating the growth plates.
Three questions to ask if your grade-school-age child sustains an ACL tear:
• What is the risk that the ACL will retear? There is no population data for this age group, but most studies have shown a rate near 5 percent, adults included.
• Why did the child tear the ACL when a tibial spine fracture is more common? That one is harder to answer, except that often we see some slight differences in knee X-rays compared with those of non-ACL-torn knees in the same age group. This could mean there may be a genetic component to the tear.
• Could the ACL tear have been prevented?
Evidence for and against ACL prevention programs in adolescent female athletes focuses on muscle balance and good mechanics. Those objectives can be very hard to achieve in the 5- to 10-year-old age group. Therefore, ACL injury prevention in the young child is likely not possible, except by teaching good healthy habits regarding exercise and sports performance.
If your child does sustain a knee injury, contact or see your doctor if the injury involves obvious deformity, knee joint swelling or does not improve with two weeks of rest.
Dr. Eric W. Edmonds is a pediatric and adolescent orthopedic sports medicine specialist at Rady Children’s Hospital-San Diego and an assistant professor of orthopedics at UC San Diego. He can be reached at sports@rchsd.org.