Posterolateral Instability of the Knee & Knee Dislocations

POSTEROLATERAL INSTABILITY   

= when stress testing the lateral tibial plateau rotates posteriorly in relation to the femur with lateral opening of joint

associated with knee dislocation (see below)

Posterolateral injury components

1. popliteus tendon

2. arcuate ligament

3. LCL and lateral capsular ligaments

Tests:

• See Knee Examination

• Check common peroneal nerve function

Management:

• Surgery always required

Preop planning:  

• X-Rays:

  • Segond fracture - avulsion fracture of lateral capsule off tibia - indicative of an associated ACL injury - seen on AP view.

• MRI 

  • allows assessement of posterolateral corner injury as well as ACL & PCL

  • assess which structures of the posterolateral corner are injured and whether the injuries are mid-substance or whether they have been avulsed from the fibula or femur