Courtesy Dr Brett Fritsch, Dr Ashok Shyam, Ortho TV

Posterolateral Corner (PLC) Injuries

Overview

The posterolateral corner (PLC) of the knee is a complex anatomical region consisting of multiple stabilizing structures. Historically, PLC injuries were considered difficult to diagnose and associated with poor outcomes. Improved understanding of anatomy, biomechanics, and reconstruction techniques has significantly improved results.

PLC injuries are commonly associated with:

Multiligament knee injuries
Knee dislocations
High-energy trauma

Functional Anatomy of the PLC

Important Structures

The clinically important structures of the PLC include:

Lateral collateral ligament (LCL)
Popliteus tendon
Popliteofibular ligament
Biceps femoris
Iliotibial band
Posterolateral capsule
Lateral meniscus
Common peroneal nerve

Functions of the PLC

The PLC acts as the primary restraint to:

Varus stress
External rotation

It also works synergistically with:

Deficiency of the PLC can therefore compromise cruciate ligament stability and reconstruction outcomes.

Classification of PLC Injuries

PLC injuries are broadly classified into:

Acute Injuries

Recent traumatic injuries
Usually associated with high-energy trauma

Chronic Injuries

Delayed or missed diagnosis
Persistent instability and gait abnormalities

Acute PLC Injuries

Mechanism of Injury

Common mechanisms include:

Road traffic accidents
Sports injuries
Knee dislocations

Road traffic accidents account for approximately 50% of severe PLC injuries.

Associated Injuries

Systemic Injuries

Acute PLC injuries may occur with:

Spine injuries
Chest trauma
Long bone fractures

Local Knee Injuries

Common associated knee injuries include:

Meniscal tears
Tibial plateau fractures
Neurovascular injuries
Multiligament injuries

Initial Management Priorities

Trauma Principles

Management begins with:

ATLS / EMST protocols
Stabilization of life-threatening injuries

Vascular Assessment

Importance

The popliteal artery is at risk in PLC injuries and knee dislocations.

Failure to identify vascular injury can result in limb-threatening complications.

Assessment Methods

Evaluation includes:

Pulse examination
Ankle–brachial index (ABI)
Doppler ultrasound
CT angiography

Vascular Assessment Algorithm

If Knee Dislocation Present

Reduce the knee immediately

If Limb Ischemia Present

Urgent angiography required

If Pulses Are Asymmetric

Perform CT angiography

If Pulses Are Normal

ABI < 0.9 ? CT angiography
ABI > 0.9 ? serial monitoring

Neurological Assessment

Common Peroneal Nerve

Peroneal nerve injury may occur in up to 25% of PLC injuries.

Examination includes:

Dorsiflexion
Foot eversion
Sensation over dorsum of foot

Tibial Nerve Examination

Assess:

Plantarflexion
Sole sensation

Stabilization of Acute Injuries

Reduction

Usually achieved with:

Gentle traction

Immobilization Options

Hinged brace
Splint
Plaster slab

Severe Instability

May require:

External fixation

Diagnosis of PLC Injuries

Diagnosis Relies On

History
Clinical examination
Imaging

Imaging

X-rays

Useful for identifying:

Fibular head avulsion fractures

MRI

Best imaging modality in acute injuries.

MRI evaluates:

Ligament injury
Meniscal pathology
Associated cruciate injuries

CT Scan

Useful when fractures are suspected.

Chronic PLC Injuries

Challenges

Diagnosis of chronic PLC injuries is more difficult because:

MRI findings may appear normal
Instability becomes subtle
Compensatory gait develops

Important Diagnostic Tools

Detailed clinical examination
Stress radiographs
Gait analysis

Clinical Examination Tests

1. Varus Stress Test

At 30°

Isolates the LCL

At 0°

Suggests combined ligament injury

2. Dial Test

Performed at:

30°
90° knee flexion

Interpretation

Increased external rotation at 30° only ? PLC injury
Increased external rotation at both 30° and 90° ? PLC + PCL injury

3. External Rotation Recurvatum Test

Assesses:

Heel elevation asymmetry
Hyperextension instability

4. External Rotation Posterior Drawer Test

Posterior and external rotational force is applied to evaluate combined instability.

5. Reverse Pivot Shift Test

Posterolateral tibial subluxation reduces during extension.

Important point:

Compare with contralateral side because specificity is limited.

6. Gait Analysis

Look for:

Varus thrust
Hyperextension gait

Stress Radiographs

Stress radiographs are especially valuable in chronic injuries.

Interpretation

2 mm opening ? isolated LCL injury
4 mm opening ? Grade III PLC injury

Principles of Management

Evidence-Based Concepts

Studies suggest:

Surgery is superior to non-operative treatment
Early surgery is superior to delayed surgery
Reconstruction plus repair is superior to repair alone

Timing of Surgery

Ideal Timing

Optimal timing is approximately:

Day 7–14 after injury
Around Day 10 is often preferred

Advantages include:

Easier dissection
Better tissue quality
Less scarring

Repair vs Reconstruction

Repair Alone

Associated with:

High failure rates (~40%)

Reconstruction Plus Repair

Provides:

Better stability
Improved long-term outcomes

Success Rates

Reconstruction

Approximately:

90% success rate

Repair Alone

Approximately:

60% success rate

Surgical Techniques

Structures Typically Reconstructed

LCL
Popliteus tendon
Popliteofibular ligament

Reconstruction Techniques

Grade II Injuries

Usually treated with:

Fibular-based reconstruction

Grade III Injuries

Require:

Tibia + fibula-based reconstruction
More anatomical restoration

Surgical Approach

Posterolateral Approach

Typically involves three windows:

Window 1

Posterior to biceps femoris
Accesses fibula and peroneal nerve

Window 2

Between biceps femoris and IT band
Accesses posterolateral capsule

Window 3

Through IT band
Accesses femoral insertion sites

Common Peroneal Nerve Protection

Identification and protection of the common peroneal nerve is mandatory during surgery.

Graft Choices

Autografts

Generally preferred.

Allografts

Acceptable if properly prepared.

Synthetic Augmentation

Emerging role, though long-term evidence remains limited.

Chronic PLC Injury Considerations

Alignment Assessment

Evaluate for:

Varus malalignment

Persistent varus overload may compromise reconstruction.

Role of Osteotomy

In chronic cases:

Osteotomy may be required
Sometimes osteotomy alone improves symptoms
Often combined with PLC reconstruction

Outcomes

Reported outcomes after reconstruction include:

Lysholm scores approximately 85–90
IKDC scores approximately 75–85

Better outcomes occur with:

Reconstruction plus repair
Proper alignment correction

Acute vs Chronic PLC Injuries

Feature	Acute Injury	Chronic Injury
Diagnostic difficulty	Easier	More difficult
Imaging	MRI useful	Stress X-rays important
Surgical strategy	Repair + reconstruction	Reconstruction ± osteotomy
Focus	Whole patient	Knee-specific evaluation

Key Takeaways

PLC injuries are complex but manageable with modern techniques
Always assess vascular status and peroneal nerve function
MRI is most useful in acute injuries
Stress radiographs are valuable in chronic instability
Early surgery within 7–14 days provides best results
Repair alone has high failure rates
Reconstruction should be combined with repair whenever possible
Chronic varus alignment may require corrective osteotomy

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