Postero-lateral Corner Stability

Question 1

When to assess Postero-lateral corner?

Answer 1

If there’s a history or clinical finding suggestive of a ligament injury

Question 2

Varus-recurvatum test

Answer 2

Lift the patient’s leg by grasping the big toe

If there’s injury to the Postero-lateral corner, the knee will fall into varus and recurvatum as the tibia externally rotates on the femur

A positive result signifies an injury not only to the postero lateral corner but also possibly the LCL and PCL as well

Question 3

Dial test

Answer 3

Patient prone

Legs are grasped just proximal to the ankles and an external rotation force applied to each leg

The degree of external rotation is compared by looking at the position of the feet

Comparison is made with the knees flexed to 30° and then at 90°

If there’s increased external rotation on the affected side at both 30 and 90° of flexion then there’s likely to be a combined PLC and PCL injury

If there’s less external rotation at90° compared to 30° in the affected side then the injury is likely to be an isolated PLC disruption

Question 4

Main structures of the PLC

Answer 4

1. LCL
2. popliteus ligament
3. Politeaofibular ligament

–> primary restraints to varus and external rotation forces

Question 5

Mechanism of injury

Answer 5

Varus injury and hyperextension

Typically high energy trauma

Rarely isolated, typically associated with cruciate ligament injury or tibiofemoral knee dislocation

Question 6

If undetected or untreated

Answer 6

Can cause severe longterm disability due to instability and cartilage degeneration

Can also jeopardise the results of concomitant ACL or PCL reconstruction

Question 7

Immediate management

Answer 7

Assessment and treatment of any associated neurovascular injury, esp to the popliteal artery or peroneal nerve

Reduction of knee dislocation

Question 8

Layers of the PLC

Answer 8

Superficial :
Biceps femoris
IT band

Middle :
Patellar retinaculum

Deep:
LCL
fabellofibular ligament
Arcuate ligament
Coronary ligament
Popliteus tendon
Popliteofibular ligament

Question 9

Arthroscopic sign

Answer 9

Camera ‘drive through sign’ occurs when an excessive amount of laxity is encountered arthroscopically, which can be an indication of PLC injury