ACL Rupture in Children

Due to the nature of the knee joint, active children are prone to knee injuries. A torn or ruptured anterior cruciate ligament (ACL) is one of the most common type of knee injuries.

Contact sports or sports that involve swift, abrupt movements such as pivoting, stopping suddenly or changing direction quickly are the most common cause of ACL injuries.

An ACL injury can also occur when a child jumps and lands on their feet with knees straight and locked instead of flexed as this puts excessive pressure on the knee joint and can cause the rope like ACL to tear and break apart.

ACL rupture is three times more common in teenage girls than in boys. This is due to: 

  • Oestrogen hormones which lead to weaker collagen
  • Anatomical tight notch
  • A wider pelvis which leads to altered mechanics and increases valgus stress on landing from a jump

ACL injuries can be very painful and can cause the child to be unsteady on their feet and have difficulty walking. Depending on the age of the child and the severity of the injury, a torn ACL often requires surgery in addition to physiotherapy.



  • Pain when bearing weight on the affected leg or at rest
  • Swelling of the knee joint which can occur within 24 hours of the injury

  • Most likely there will be some instability when walking and the feeling of being unstable or ‘wobbly’ on the leg as well as the sensation of the knee feeling not as tight or compact as it was previously

  • Often children will report hearing a ‘pop’ sound which occurs when the ligament tears

If a child has suffered a knee injury they should stop activity immediately and seek medical attention to prevent any further injury to the knee. 

In the interim, the knee should be iced regularly for 20 minute intervals. The knee should be elevated as much as possible to reduce swelling. It is advised not to bear weight on the affected leg.



Treatment of an ACL rupture in children differs from the standard treatment for an ACP rupture in an adult. A child or adolescent knee varies anatomically and physiologically from an adult knee and thus the treatment needs to reflect these differences. 

The main difference is the growth plates or epiphysis in a child’s knee.  These are regions at the end of the femur and tibia of developing tissue and account for the majority of the growth of the leg.  These sections are usually the weakest part of the knee.  The same injury that would tear a ligament or cartilage in a mature knee is much more likely to fracture the bones through the growth plate in a child.

The complication in children undergoing ACL reconstruction, is the growth plates of the knee are directly in the path of where the holes would be surgically drilled in the bone to attach the new ligament.  A standard ACL reconstruction in a growing child or adolescent without any consideration for this factor can cause a growth abnormality leading to leg length inequality or to angulatory deformity at the knee.  The younger the child, the higher the risk of this occurring.

Thus, non-operative treatment is usually suggested initially.  This involves strapping the leg, prescribing strengthening exercises as well as abstaining from activity.

When a child stops growing, the growth plate hardens (ossifies) along with the rest of the bone. Girls tend to stop growing earlier than boys; their growth plates usually close around ages 14 or 15. Boys' growth plates close later, at around 16 or 17.

If the adolescent is close to skeletal maturity, the risks are small and a standard ACL reconstruction is usually performed. 

In a younger child alternative techniques have been developed to reduce the possibilities of growth complications.  These techniques involve placing the ligament graft in a non-anatomic position or one that does not quite duplicate normal ligament function.  This is done by either drilling holes that go around rather than through the growth plates or by avoiding holes altogether and wrapping the graft around the bone.  Growth abnormalities can still occur, but the incidence is much less than with standard techniques.

These procedures are designed to be a temporary measure to control symptoms until skeletal maturity, when a traditional reconstruction can be performed. Such interventions have been quite successful, with many children returning to sports and not needing a second procedure later on.


Rehab and Recovery

Recovery from ACL surgery is a lengthy process and physiotherapy is required to restore full range of motion and function of the knee.

A full rehab program complete with daily strengthening exercises will be explained and the child will be on crutches for four to six weeks post surgery.