Adolescent ACL Tears With Meniscal Injury: Injury Patterns Across Developmental Stages (1)

After an anterior cruciate ligament (ACL) tear in an adolescent, whether the meniscus is injured at the same time is an important part of assessing the severity of knee injury.

The knees of children and adolescents are still developing. The same twisting injury can produce different injury patterns at different ages and stages of skeletal maturity. Younger children are more likely to have an avulsion at the tibial insertion of the ACL, while after puberty the injury pattern gradually shifts toward midsubstance ACL tears and meniscal injuries become more common.

Treatment also needs to consider whether the physes have closed, remaining growth potential, knee stability, and future sports demands.

The ACL lies inside the knee joint. One of its main roles is to limit excessive forward movement of the tibia relative to the femur, while also helping control knee rotation. During sudden stopping, cutting, or landing in sports such as football, basketball, or skiing, the knee may experience large rotational and shear forces over a short period of time.

A substantial proportion of ACL injuries in children and adolescents are non-contact injuries. There may be no direct collision with another person; the injury occurs during turning, landing, or deceleration. Once the ligament loses its stabilizing function, abnormal movement may occur between the tibia and femur. The meniscus, located within the joint space, then has to take on more stabilizing and shock-absorbing work. It may tear during the first injury or gradually become injured during repeated giving-way and twisting episodes after the ACL injury.

The menisci can be understood as two fibrocartilage structures inside the knee that provide cushioning and stability. They distribute joint pressure, improve the fit between the femur and tibia, and contribute to joint stability. When a young patient has both ACL and meniscal injury, doctors usually pay close attention to preserving as much meniscal tissue as possible because adolescents have many years of sports and joint use ahead of them.

A child’s knee has an important structure that adults no longer have: an open physis, commonly called the growth plate. The distal femoral and proximal tibial physes are closely related to continued lower-limb growth.

In younger children, the bone around the ACL attachment has not fully matured. When force acts on the knee, the ligament itself may not completely rupture; instead, the ACL attachment on the tibia may be pulled away first, creating a tibial eminence or tibial insertion avulsion injury.

For this reason, tibial spine avulsion fractures are more common before puberty. In later adolescence, as the skeleton matures, typical midsubstance ACL tears become more frequent. The ACL itself changes with growth, and data suggest that the ACL grows relatively quickly between ages 13 and 15, a period when injury risk is also concentrated.

This developmental change explains why a 10-year-old child and a 16-year-old adolescent may face very different injury patterns, growth-related risks, and surgical strategies.

Children before puberty and with younger bone age usually have substantial remaining lower-limb growth. Tanner stage, bone age, and estimated remaining growth are commonly used clinically to assess maturity.

For example, a child with more than 7 cm of expected lower-limb growth remaining and around Tanner stage 1 may be considered to have large remaining growth potential.

For this age group, if there is only a stable partial ACL tear, no clear rotational instability, and no important meniscal or cartilage injury, doctors may consider nonoperative treatment with close follow-up.

If the knee remains clearly unstable or if a meniscal injury already needs treatment, continued waiting may lead to new joint damage. Surgery may need to be considered even in a younger child, but the surgical plan must be designed to minimize impact on the growth plate.

After puberty begins, the body undergoes obvious changes in height, weight, and bone structure, while muscle strength, neuromuscular control, and movement coordination may not keep pace fully.

Female adolescents deserve particular attention. After ages 12 to 13, the incidence of ACL injury in girls increases markedly, and ages 13 to 15 may be a period of higher ACL injury susceptibility.

After rapid skeletal growth in adolescent girls, if lower-limb muscle control and strength do not improve in parallel, the knee may experience larger abnormal loads during jumping, landing, sudden stopping, and cutting.

In boys, the age at which ACL injury incidence rises noticeably is usually slightly later and may be concentrated around ages 14 to 15.

At this stage, midsubstance ACL tears become increasingly common. At the same time, because sports intensity is higher and body weight and speed increase, the meniscus is exposed to greater forces.

For adolescents who regularly participate in football, basketball, or other sports requiring rapid cutting, continuing high-intensity activity after an ACL rupture and repeated knee instability can place the meniscus under ongoing extra shear stress.

When girls have a bone age over about 14 years, boys over about 16 years, or Tanner stage reaches 4 to 5 with little remaining lower-limb growth, the biology of the knee gradually approaches that of an adult knee.

At this stage, typical midsubstance ACL tears are seen more often, and medial meniscal, lateral meniscal, cartilage, or other ligament injuries may also be present.

Surgical strategy also changes. Because the physes are close to closure, the growth-plate constraints during ACL reconstruction are reduced, and some patients can undergo reconstruction techniques closer to adult anatomic reconstruction.

Being close to adult biology does not mean the risk is identical to that in adults. Adolescents often have high sports demands and a strong desire to return to pivoting sports such as football and basketball, so reinjury after ACL reconstruction remains a major concern.

The risk of reinjury after ACL reconstruction in children and adolescents should not be overlooked. Both graft reinjury on the operated side and ACL injury in the opposite knee can occur.