What is the anterior cruciate ligament?
The ACL (anterior cruciate ligament) is located in the centre of the knee joint in the intercondylar notch of the femur, extending obliquely to the tibia. It is the most important component of knee stability. Its main role is to prevent excessive anterior translation of the tibia relative to the femur and to ensure good rotational stability of the knee.
After ACL rupture, most people experience instability – a feeling that the knee gives way. Due to the activity patterns typical for their age, children frequently change direction, and after ACL rupture feel that their knee "gives way or dances". Children are not small adults; ACL injuries in children and adolescents have their own specific characteristics.
Why are ACL injuries multiplying in children?
ACL injuries in children have multiplied over the last two decades. The cause is believed to be early, highly specialised and intensive sports activity – children specialise early in one sport, train intensively, and injury prevention programmes are not implemented. The decline in unstructured outdoor play is another contributing factor.
Girls are at greater risk: increased ligament laxity, a thinner ACL, characteristic anatomical relationships and hormonal factors all play a role. ACL rupture most commonly occurs as a non-contact injury from combined valgus and rotational forces during sports with frequent direction changes, such as football, handball or basketball.
Diagnosis
Children describe a characteristic sporting event – "the knee popped out and came back". The injury usually occurs during a sudden change of direction or landing. They often feel or hear something snap, followed by severe pain, swelling and inability to continue playing.
After the acute injury, clinical examination is difficult because the knee is swollen and the muscles are tense; reassessment one week later is recommended. Until then: elastic bandage, cold compresses, analgesia and range of motion exercises.
At the follow-up visit, specific stability and meniscal tests are performed. MRI is needed for definitive confirmation and to identify associated injuries, especially meniscal tears. Analysis of the MRI also determines the tear location, as some types of ACL tears are suitable for acute primary repair.
Treatment
Children are considered to have clinically significant instability after ACL rupture that puts them at excessive risk of additional cartilage and meniscal injury over time. Therefore, the current view is that appropriate knee stability should be achieved surgically for all children.
Conservative treatment (without surgery)
Only indicated for partial ACL tears: the knee is positioned in a long orthosis at 10° flexion for 5 weeks, followed by intensive physical therapy.
Primary repair (suturing)
An acutely diagnosed complete ACL tear at its attachment site can be treated arthroscopically by suturing the ACL back to its anatomical attachment point.
ACL reconstruction
The most commonly performed operation today. Grafts (replacement ligaments) are taken from tendons of the same knee. Because drilling through the growth plates is required, assessing skeletal maturity is critically important in children – approximately 70% of leg length growth occurs from the growth plates around the knee, so the surgical technique must be as sparing of these structures as possible.
Simultaneous meniscal repair is performed if a tear is present. Lateral extra-articular augmentation is increasingly added to improve rotational stability.
Approximately 70% of leg length growth occurs from the growth plates around the knee. This makes surgical technique selection critically important in children – the procedure must preserve the growth plates wherever possible.
Rehabilitation
Post-operative rehabilitation follows a structured progression:
- Full range of motion restoration
- Strengthening – with particular emphasis on hamstring muscles
- Return to daily activities
- Return to full sport at approximately one year after surgery