Posterolateral Corner (PLC) Injury

What is a posterolateral corner injury?

The posterolateral corner — the PLC — is the group of structures on the outer-back of the knee that work together to control rotation and provide stability. It includes ligaments, tendons and a capsule, all working as a coordinated unit.

PLC injuries usually happen from a significant force to the front-inner side of the knee, or from a hyperextension or twisting injury. They can occur in isolation but more often happen alongside other ligament injuries — particularly the ACL or PCL.

PLC injuries are sometimes missed in the early aftermath of a major knee injury, which can have significant consequences. Identifying them is critical to the right management plan.

What does it feel like?

Symptoms vary depending on the grade of injury and what else is involved. You may notice:

• Pain on the outer side of the knee

• A feeling that the knee gives way, particularly when pivoting outward

• Swelling and bruising on the outer side

• A sense that the knee hyperextends or buckles backwards

• Numbness or weakness in the foot, if a nearby nerve has also been affected

In multi-ligament injuries, the picture is dominated by the overall instability rather than the PLC component specifically.

How is it diagnosed?

Diagnosis requires a careful, experienced examination. Specific tests assess how the knee behaves under particular forces — and small differences from one side to the other can be very telling.

MRI is essential and gives detailed information about which structures are involved. In some cases additional imaging is helpful, particularly when there's bony involvement or alignment changes that may need to be addressed alongside the soft-tissue injury.

Importantly, in any major knee injury — particularly when the ACL or PCL is involved — the PLC must be specifically assessed, because missing it has lasting consequences.

What are the treatment options?

Lower-grade PLC injuries occasionally heal with non-surgical management, but most significant PLC injuries need surgical repair or reconstruction — particularly when other ligaments are also involved.

The timing of surgery matters: acute repair within a few weeks of the injury is often preferable to delayed reconstruction. The decision and approach are individual and reflect the full picture of the injury — Nev will work through this with you at your consultation.

When should you get it checked?

Seek a specialist assessment if:

• You've had a major knee injury, particularly one with multiple ligaments suspected

• The knee feels grossly unstable or buckles backwards

• You've had an ACL or PCL diagnosis but no clear assessment of the PLC

• There's pain, swelling or bruising on the outer-back of the knee

• You're not progressing as expected with rehabilitation

PLC injuries are time-sensitive. Early identification and the right plan from the outset make a substantial difference to long-term outcomes.