Posterolateral Rotatory Instability of the Knee

Posterolateral rotatory instability can occur due to damage to the structures that support the outside of the knee joint, described as the posterolateral corner. These structures are critical to preventing symptoms of knee instability. An injury of the knee ligaments can affect the structures of the posterolateral corner.

These structures include the lateral collateral ligament, the popliteus tendon, and the knee joint capsule. They can be injured when the knee sustains ligament damage—including ACL tears and PCL tears. If damage to the posterolateral corner is not treated, persistent knee problems can occur, despite treatment of other knee injuries.

Older woman with knee injury
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Symptoms of Posterolateral Corner Injuries

Posterolateral corner injuries often occur with knee dislocations.

About 70% of posterolateral corner injuries occur in the setting of an injury to the ACL and/or PCL—also known as the cruciate ligaments.

About 15% of posterolateral corner injuries also involve injuries of the peroneal nerve. An injury to this nerve can cause numbness down the outside of the leg or weakness of the foot.

About 20-30% of the time, an injury of the posterolateral corner is isolated.

Symptoms of posterolateral corner injuries include:

  • A feeling that the knee is going to give out
  • Pain and swelling over the outside of the knee joint, toward the back of the knee

Your doctor will perform a Dial test when examining your knee for posterolateral rotatory instability. During this test, your doctor will determine the rotation of your knee (by turning your foot outwards at a specific position) and compare it to the opposite knee. Excessive rotation is indicative of an injury to the posterolateral corner.

Your doctor will check the degree of rotation at different levels of knee flexion to determine which structures have been injured.


Treatment of a posterolateral corner injury depends on the degree of instability. This type of injury is considered a contributing reason for why some people might not improve after ACL reconstruction surgery.

When posterolateral corner injuries cause significant instability in the knee joint, the structures can be surgically repaired. A surgical repair requires an incision along the outside of the knee joint.

If the injuries to the ligament are recent, they can often be repaired without the use of donor tissue, whereas chronic injuries may require donor tissue to reconstruct the damaged structures. Severe injuries also generally require the use of some donor tissue to augment the repair along the outside of the knee.

Rehab After Surgery

Rehabilitation after posterolateral reconstruction will depend on which knee structures that have been injured and repaired.

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