Knee

Posterolateral Corner (PLC) of the Knee — Imaging Anatomy Overview

The posterolateral corner (PLC) is a complex stabilising region of the knee that resists varus stress, external tibial rotation, and posterior translation, particularly when the knee is near extension. Understanding its anatomy is critical in MRI interpretation, as PLC injuries often accompany cruciate ligament tears and, if unrecognised, can lead to persistent instability and graft failure after reconstruction.

Key Anatomical Components

1. Static stabilisers

Fibular (lateral) collateral ligament (FCL/LCL) – runs from the lateral femoral epicondyle to the fibular head. Best seen on coronal T2-weighted MRI. It is extra-articular and lies superficial to the popliteus tendon.
Popliteus tendon and muscle – originates from the posterior tibia above the soleal line and inserts on the lateral femoral condyle, coursing deep to the FCL. Seen as an oblique low-signal band on axial and coronal images.
Popliteofibular ligament (PFL) – extends from the musculotendinous junction of the popliteus to the fibular head. It acts as a key stabiliser against external rotation and is best appreciated on coronal oblique MRI.
Arcuate ligament complex – a condensation of posterolateral capsule fibres that arch over the popliteus tendon to insert on the fibular styloid and lateral tibial plateau.

2. Dynamic stabilisers

Biceps femoris tendon – inserts on the fibular head and lateral tibial plateau; provides dynamic resistance to varus and external rotation.
Lateral head of gastrocnemius – arises from the lateral femoral condyle; visible posterior to the FCL.
Iliotibial band (ITB) – provides lateral stabilisation, inserting on Gerdy’s tubercle.