Knee extensor mechanism : structure, traumas and interventions

The knee extensor mechanism is a complex joint mechanism that plays an essential role in lower limb mobility. It is made up of three key elements which, when working together, allow for active knee extension. These elements are the kneecap (also called the patella), the quadriceps tendon (allowing the quadriceps muscle to extend) and the patellar tendon.

Structure and function :

• Kneecap (Patella) : a sesamoid bone that sits between the quadriceps tendon and patellar tendon, the patella has a pulley action that increases the efficiency of the extensor mechanism.
• Quadriceps tendon : this is the interface between the quadriceps muscle and patella, facilitating the transmission of force during extension.
• Patellar tendon : this tendon is crucial for transmitting forces produced by the quadriceps, thus allowing knee extension.

Traumas and interventions :

• Kneecap (patella) fracture : direct impact or excessive tensile forces can result in a patella fracture. This occurrence is covered in more detail in the section on knee fractures.
• Rupture of the quadriceps tendon : this rupture can manifest acutely following a trauma, or chronically from repeated microtraumas. The injury often occurs where the tendon attaches to the kneecap. The severity of the rupture can vary:

• Partial tears : these can often benefit from conservative treatment without surgery.
• Complete ruptures : these severe lesions compromise the continuity of the extensor mechanism, leaving the patient unable to extend the knee. In this case, surgical intervention is necessary to repair and reattach the tendon to the patella.

• Patellar tendon rupture : this type of rupture can also occur through acute or chronic trauma. Like the quadriceps tendon, a complete rupture will make it impossible to extend the knee, and surgery will be required. Surgery aims to restore the function of the extensor apparatus by repairing the damaged tendon.

Conclusion : the integrity of the extensor mechanism is essential for knee function and mobility. In the event of injury, rapid, appropriate treatment is the key to guaranteeing optimal recovery and restoring normal knee function.