22/03/2026
Posterolateral Corner (PLC) of Knee: The Hidden Stabilizer
This image highlights the posterolateral corner (PLC) of the kneeāone of the most complex yet often overlooked stabilizing regions. It is not a single structure but a functional network of ligaments, capsule, and muscles working together to control rotation and lateral stability.
At the core of this system are the fibular collateral ligament (FCL), popliteus tendon, and popliteofibular ligament, which together resist varus forces (outward opening of the knee) and external rotation of the tibia. These structures act as the primary static stabilizers on the lateral side, especially when the knee is slightly flexed.
The popliteus muscle plays a critical dynamic role. It āunlocksā the knee from full extension by internally rotating the tibia and also provides posterior and rotational stability. Its expansionsāboth capsular and fibularāintegrate it into the entire PLC system, making it a key link between movement and stability.
The posterior capsule and oblique popliteal ligament (OPL) reinforce the back of the knee, preventing excessive hyperextension. These structures work closely with the PCL, which resists posterior translation of the tibia. Together, they form a strong posterior restraint system.
On the medial side, structures like the superficial MCL (sMCL) and posterior oblique ligament (POL) balance the lateral system, ensuring that forces are evenly distributed across the joint. This medial-lateral balance is essential for maintaining proper alignment during movement.
Biomechanically, the PLC is crucial during activities involving cutting, pivoting, and deceleration. It prevents excessive rotation and lateral instability when the knee is under load. Without proper PLC function, forces shift abnormally to the ACL and PCL, increasing injury risk.
Clinically, PLC injuries are often missed but have major consequences. Untreated damage can lead to:
Persistent knee instability
Failure of ACL/PCL reconstructions
Abnormal gait and joint degeneration
š The key concept is that the knee is not just a hingeāit is a rotationally controlled joint, and the PLC is essential for that control.