Posterolateral corner
The posterolateral corner of the knee is a complex of structures located on the back and outside of the knee, which connects the femur to the tibia and fibula. It is formed by several structures, including the lateral collateral ligament, the popliteofibular ligament, the popliteal tendon and the posterolateral capsule of the knee. It plays an important role in stabilizing the joint, mainly preventing excessive varus opening of the joint.
Isolated injuries to the posterolateral corner are rare. They are usually associated with other ligament injuries, such as the posterior cruciate ligament.
How the Injury Occurs
The trauma mechanism most frequently associated with posterolateral corner injuries is direct trauma to the front and inner side of the knee directed toward the back and outer side (varus), with the knee close to full extension. This creates an opening in the outer side of the joint, which can injure the structures of the posterolateral corner.
This type of trauma is not common in low-energy sports such as soccer, basketball, handball, among others. Injuries usually occur in high-energy trauma, such as in motorcycle or car accidents and falls from heights.
What the Patient Feels
Injuries to the posterolateral corner of the knee involve a significant twisting mechanism of the knee, with a lot of energy involved. During the twisting, the patient may hear a popping sound and, immediately after the trauma, the knee may be very painful and swollen.
It is important for the patient to seek medical attention if there is a twisted knee, because when there is a suspicion of an injury to the posterolateral corner of the knee, a more detailed investigation should be carried out and the patient should be immobilized for the first few days.
After a few weeks of injury, the patient may present instability in the outer side of the knee, which may be felt as an opening on the external part of the knee when walking.
Since injuries to the posterolateral corner of the knee are usually associated with injuries to other ligaments, it is important that a thorough physical examination be performed.
Complementary Exams
Some imaging exams are important to help the doctor to diagnose injuries to the posterolateral corner of the knee. The main one is the nuclear magnetic resonance imaging of the knee, which can identify the injured structures. Plain and stress X-rays of the knee can also help. It is worth noting that imaging exams alone are not enough to make a diagnosis. A detailed physical examination to assess ligament instability is the most important.
Treatment
The indication for treatment of posterolateral knee injuries depends on the stability of the knee. Isolated and stable injuries can be treated without surgery, with immobilization, analgesic and anti-inflammatory medications, and physical therapy.
Unstable injuries or those associated with other knee ligament injuries should be treated surgically.
Several surgical techniques are described for the treatment. In the acute phase, an option to repair the structures can be considered. However, in general, reconstruction of all torn ligaments is performed. After the surgical procedure, the patient usually has the knee immobilized for 6 weeks.
Physical therapy plays an important role both before and after surgical treatment. Since posterolateral knee injuries are not so common, the physical therapist should have experience with rehabilitation protocols.
