What is the posterolateral corner of the knee?

The main parts

• Lateral collateral ligament (LCL): a cord-like ligament from the outer thigh bone to the head of the fibula, resisting outward bowing
• Popliteus tendon: runs from the outer thigh bone around the back of the knee to a muscle behind the shin, controlling rotation
• Popliteofibular ligament: links the popliteus tendon to the fibula and adds rotational control
• The posterolateral capsule and nearby tendons, including the biceps femoris, which add further support

What it does

Together these structures stabilise the outer side of the knee. They prevent the knee from opening on the outside, limit the shin from rotating outward too far, and help stop the knee bending backward. They also work with the cruciate ligaments, especially the PCL and ACL, so injury to one group puts extra load on the other.

Why injuries here matter

Isolated injuries to the posterolateral corner are uncommon. Most happen alongside an ACL or PCL tear, often after a significant force such as a sports collision, a fall from height or a road traffic accident. Because the swelling and pain may be blamed on the cruciate tear alone, the outer-side injury can be missed.

When a significant posterolateral corner injury is left untreated, the knee may feel wobbly when standing and walking, a pattern sometimes called a varus thrust, and any cruciate reconstruction is under extra strain.

If your report mentions it

MRI reports may name the individual parts, such as LCL sprain, popliteus tendon tear or fibular head avulsion. Bring the report and images to your appointment. At Aman Hospital in Doha, Dr. Gelber examines rotation and side-to-side stability to judge how much these findings affect the way your knee works, which determines whether treatment is a brace, repair or reconstruction.