LCL and Posterolateral Corner (PLC) Injuries

The posterolateral corner is one of the most commonly missed injuries in the knee. That matters, because if it is not identified and treated, it can undermine everything else – including ACL or PCL reconstructions that might otherwise succeed. When I see a patient with outer-side instability, my first priority is working out exactly which structures are damaged and how that instability fits into the bigger picture.

Lateral collateral ligament (LCL) injuries and posterolateral corner (PLC) injuries affect the stabilisers on the outer side of the knee. These structures control side-to-side stability and, critically, rotational stability. Many lower-grade LCL sprains heal well with rehabilitation, but higher-grade PLC injuries frequently need surgical reconstruction to restore reliable function.

What are the LCL and the posterolateral corner?

LCL (lateral collateral ligament)

The LCL is a strong ligament on the outside of the knee. It resists the knee opening up on the outer side (varus stress) and contributes to stability during cutting and pivoting.

Posterolateral corner (PLC)

The PLC is not a single structure – it is a group of stabilisers at the back-outside of the knee that work together to control:

External rotation of the shin bone
Varus (outer-side opening) stability
Posterior and rotational stability in combination with the PCL and ACL

Because the PLC involves multiple structures, these injuries are sometimes missed on initial assessment. Getting the diagnosis right early makes a real difference to outcomes.

How do LCL and PLC injuries happen?

These injuries typically follow significant force:

A blow to the inside of the knee causing the outer side to stretch (varus stress)
Hyperextension injuries (knee forced too straight)
High-energy trauma (road traffic collisions, falls)
Sports injuries (contact, awkward landings, high-speed pivots)
Knee dislocation patterns (even if the knee relocates spontaneously)

LCL/PLC injuries frequently occur alongside ACL or PCL injuries. Meniscus and cartilage damage can also be present.

Symptoms of LCL/PLC injury

Pain and tenderness on the outer side or back-outside of the knee
Swelling and bruising (often more noticeable laterally)
A feeling the knee is unstable, particularly with turning or on uneven ground
The knee feels as if it opens on the outside (varus instability)
Difficulty trusting the knee during pivoting or deceleration
Sometimes a sensation of the knee shifting backward or outward with movement

Red flags

Severe lateral injuries can occur in high-energy trauma. Seek urgent assessment if you have numbness or weakness in the foot (including foot drop), a cold or pale foot, severe swelling, or suspected knee dislocation.

How I assess LCL and PLC injuries

These injuries require careful evaluation of stability in multiple directions. I test varus stability, rotational stability (the dial test), and always assess the ACL, PCL and MCL at the same time – it is rare for a significant PLC injury to exist in complete isolation.

I also check neurovascular status carefully. The common peroneal nerve runs right past the posterolateral corner, so nerve injury (including foot drop) needs to be identified early.

Imaging typically includes X-rays to look for fractures and avulsions, and an MRI to map exactly which ligaments are torn and whether there is meniscus or cartilage damage. In chronic cases with varus alignment, I may also arrange long-leg alignment films – this is important for surgical planning.

Getting the full picture matters because untreated PLC laxity is one of the main reasons ACL or PCL reconstructions fail.

Non-surgical treatment

Some lower-grade LCL sprains heal well with structured non-operative care:

Activity modification and swelling control
Bracing to protect the lateral side during early healing
Physiotherapy to restore movement, strength, and neuromuscular control
Return to sport guided by functional milestones, not just time

However, higher-grade PLC injuries are less likely to heal reliably with rehabilitation alone, particularly when rotational instability is significant or when other ligaments are also torn.

When surgery is needed

I consider surgery when the knee remains unstable, when injury severity is high, or when PLC laxity would compromise an ACL or PCL reconstruction.

LCL/PLC repair (acute injuries)

Repair can work well when there is a clean avulsion-type injury – where the ligament has pulled off bone and can be reattached. It relies on good tissue quality and is time-sensitive; if too much time passes, the tissue quality deteriorates and repair becomes unreliable.

LCL/PLC reconstruction

Reconstruction rebuilds the damaged stabilisers using graft tissue. I typically recommend reconstruction when:

There is high-grade instability or a complete PLC disruption
The injury is chronic and tissues have healed in a lengthened or scarred position
There is combined ligament injury (for example PCL + PLC or ACL + PLC)
Rotational instability is persistent and affecting function

The goal is to restore both side-to-side and rotational control, which is essential for reliable long-term stability.

PLC reconstruction techniques: Arciero-type and LaPrade-type

Because the PLC is a complex stabilising unit, I adapt the reconstruction technique to match the specific injury pattern. The two main approaches I use are Arciero-type and LaPrade-type reconstructions.

Both aim to reduce giving way, protect the knee during pivoting, and – importantly – reduce strain on any ACL or PCL grafts when I am reconstructing multiple ligaments at the same time.

The choice between techniques depends on which structures are torn, whether the injury is acute or chronic, your alignment, and whether other ligaments need reconstruction simultaneously. I discuss the reasoning with each patient so you understand why one approach suits your knee better than the other.

Alignment and combined procedures

In chronic PLC deficiency, limb alignment is a major factor in whether a reconstruction will hold. If the leg is significantly varus (bow-legged), the outer-side structures are constantly overloaded – and a reconstruction done without correcting alignment is much more likely to stretch out over time.

Where alignment is a problem, I may recommend an osteotomy to correct it, either before or at the same time as the PLC reconstruction.

When ACL or PCL injuries coexist, I plan the sequence and combination of procedures carefully to restore balanced stability across the whole knee.

Recovery and rehabilitation

Rehabilitation after LCL/PLC surgery is structured and protective in the early stages, because the reconstructed structures are under stress during rotation and side-to-side movements.

Key rehab priorities:

Swelling control and restoring safe range of motion
Protected weight-bearing with bracing
Progressive strengthening of quadriceps, hamstrings, hips and core
Neuromuscular training to restore control in cutting, pivoting and deceleration
Return-to-running and sport progression based on milestones and objective testing

Recovery timelines vary, especially in multiligament cases. I tailor the plan to your reconstruction, any associated injuries (meniscus, cartilage), and your goals.

Risks and considerations

All surgery carries risks. For LCL/PLC reconstruction, these include:

Infection, blood clots, wound healing problems
Stiffness or prolonged swelling
Persistent instability or graft failure (particularly if alignment is not addressed)
Nerve irritation or injury – the common peroneal nerve lies immediately adjacent to the PLC, which makes it vulnerable during both the injury itself and surgery. I take great care to identify and protect it, but this is a real risk that I always discuss
Ongoing pain or difficulty returning to high-demand pivoting sport

I go through the expected benefits, alternatives, and the rehabilitation commitment required before we proceed.

Frequently asked questions

Are LCL and PLC injuries the same thing?

No. The LCL is one ligament. The PLC is a group of stabilising structures at the back-outside of the knee. They are often injured together, and PLC injury is particularly important because it strongly influences rotational stability.

Can a PLC injury heal without surgery?

Lower-grade sprains may improve with bracing and rehabilitation. High-grade PLC injuries often do not heal reliably and typically require reconstruction, especially in active patients or when other ligaments are also torn.

Why does PLC injury matter if I'm having ACL or PCL surgery?

This is one of the most important questions in ligament surgery. Untreated PLC laxity places extra strain on ACL or PCL grafts and is a well-recognised cause of graft failure. Identifying and addressing PLC injury is essential for a durable reconstruction.

Can I be assessed for LCL/PLC injury in Bristol?

Yes. I see patients with lateral ligament and posterolateral corner injuries at my clinics in Bristol. I offer both rehabilitation-led management and reconstruction (including Arciero-type and LaPrade-type techniques) depending on the injury pattern.