Adolescent ACL Tears With Meniscal Injury: Injury Patterns Across Developmental Stages (2)

After an ACL tear, if the knee remains unstable for a long time, abnormal rotation and forward translation can increase the load on the meniscus and articular cartilage.

When ACL reconstruction in children and adolescents is delayed for more than 12 weeks, the risk of meniscal injury increases by about 4.3 times, and the risk of irreparable meniscal injury increases by about 3.2 times. A surgical delay of about 3 months has been associated with increased medial and lateral meniscal injuries.

These numbers do not mean that every adolescent ACL tear must be operated on within a fixed deadline. Whether early surgery is needed should be judged according to whether the ACL tear is partial or complete, whether the knee repeatedly gives way, whether meniscal injury is already present, skeletal maturity, and sports demands.

After the ACL loses function, the meniscus has to share more of the work of stabilizing the knee. The medial meniscus is relatively less mobile and may act like a secondary stabilizer in a chronically ACL-deficient knee.

If the knee repeatedly moves abnormally forward or rotates, stress on the medial meniscus gradually increases. Some children may have no obvious medial meniscal tear on the first MRI, but develop a new injury after months of repeated instability.

Assessment of adolescent ACL injury usually includes the injury mechanism, physical examination, and imaging.

Doctors will ask whether the injury occurred during sudden stopping, cutting, or landing; whether the child heard or felt a pop; whether the knee swelled quickly; and whether obvious instability occurred afterward.

The Lachman test, anterior drawer test, and pivot-shift test can help assess ACL stability. However, children may naturally have more ligament laxity than adults, and pain or guarding after injury can affect the examination, so comparison with the other knee is usually needed.

MRI is an important examination for evaluating the ACL, meniscus, cartilage, and other ligaments. It has good diagnostic value for pediatric ACL injuries, but accuracy may be lower in children under 12 years old, so in a few cases other examinations or even arthroscopy may be needed.

X-rays also have a role. They can help detect tibial spine avulsion fractures and assess whether the physes are open. For children with substantial remaining growth, doctors may further evaluate bone age, lower-limb alignment, and remaining growth.

For younger children with clearly open physes, treatment should protect the growth plate as much as possible. If ACL reconstruction is truly needed, physeal-sparing, all-epiphyseal, or other pediatric reconstruction techniques may be considered according to bone age and growth potential.

After puberty begins and remaining growth gradually decreases, partial transphyseal reconstruction techniques may be considered. Near skeletal maturity, reconstruction may be closer to adult ACL reconstruction.

The presence of meniscal injury also affects treatment timing and strategy. If a meniscal tear is still repairable, preserving the meniscus is usually important. With repeated twisting injuries and longer delays, some tears that might originally have been repairable may enlarge.

In practice, doctors are addressing two issues at the same time: restoring the stability provided by the ACL and protecting the meniscus and articular cartilage as much as possible.

For children whose physes have not closed, ACL reconstruction requires special attention to the growth plate. The position, diameter, angle, and fixation method of the bone tunnels may all affect the physis.

Possible growth-related problems include limb-length difference and alignment abnormalities such as valgus or varus. The level of risk is related to remaining growth potential, tunnel design, and the specific surgical technique, so preoperative skeletal maturity assessment becomes more important when the child is younger.

Reinjury after adolescent ACL reconstruction is also not rare. Fast recovery of athletic ability does not mean that the graft and neuromuscular control have fully recovered. Young athletes who return to sport before 9 months after surgery have a markedly higher risk of another ACL injury than those who delay return; one report estimated the risk at about 7 times higher.

For this reason, return to sport should require more than “no pain” or “able to run.” Strength, balance, jumping, landing control, proprioception, and side-to-side symmetry should be assessed.

If a child twists the knee during sport and then has obvious swelling, cannot continue playing, feels knee instability, or has repeated giving-way, further evaluation should be considered.

Locking, catching, and inability to fully straighten the knee also require assessment for possible meniscal injury.

Adolescent ACL tears with meniscal injury cannot be treated according to chronological age alone. Two 13-year-old children may differ in bone age, growth rate, physeal status, sport, and injury severity.

For patients with milder injuries, stable knees, and lower sports demands, structured rehabilitation and follow-up may be an option. For adolescents with complete ACL tears, repeated knee instability, or important meniscal injury, surgical treatment should be evaluated more actively.

The goal of treatment is not only to help the child return to sport, but also to protect the developing knee as much as possible and preserve better joint function for the decades ahead.