POSTEROLATERAL CORNER (PLC) INJURIES
INTRODUCTION
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Injuries to the posterolateral corner are functionally disabling and frequently challenging to diagnose.
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Due to the complex anatomy and subtle clinical presentation, PLC injuries have historically been under-recognized.
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Isolated PLC injuries are uncommon (?1.6%) and most often occur in combination with cruciate ligament injuries, particularly ACL or PCL tears (43–80%).
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A high association exists with tibial plateau fractures (up to 68%).
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Failure to identify and treat a PLC injury is a well-known cause of cruciate ligament reconstruction failure.
FUNCTION
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The popliteus tendon functions synergistically with the PCL to control external tibial rotation, varus alignment, and posterior tibial translation.
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The popliteus–popliteofibular ligament complex provides maximal restraint to external rotation when the knee is flexed.
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The lateral collateral ligament (LCL) is the primary restraint to varus stress, contributing approximately:
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55% at 5° of knee flexion
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69% at 25° of knee flexion
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ETIOPATHOGENESIS
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Common causes include:
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Sports-related trauma (?40%)
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Motor vehicle accidents
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Falls from height
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Mechanisms of injury:
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Direct blow to the anteromedial aspect of the knee
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Hyperextension injuries
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Varus loading forces
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Non-contact mechanisms involving hyperextension, varus stress, or excessive external tibial rotation
Role of PLC:
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The PLC resists lateral joint opening and prevents varus thrust during gait.
CLINICAL FEATURES
Acute phase:
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Posterolateral knee pain
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Swelling
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Anteromedial joint line tenderness
Chronic phase:
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Subjective instability
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Varus thrust gait
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Difficulty with running and cutting activities
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Episodes of giving way, especially during stair descent or pivoting movements
EXAMINATION FINDINGS
Acute signs:
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Knee swelling
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Ecchymosis and abrasions
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Antalgic gait
Chronic signs:
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Varus malalignment
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Asymmetric knee hyperextension
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A thorough assessment of peroneal nerve function is essential due to the risk of associated nerve and vascular injury.
SPECIAL TESTS
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External rotation recurvatum test
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Posterolateral drawer test – suggests injury to the popliteus tendon or popliteofibular ligament
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Varus stress test
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Dial test
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Increased external rotation at 30° ? isolated PLC injury
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Increased rotation at 30° and 90° ? combined PLC and PCL injury
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Reverse pivot shift test – demonstrates posterior tibial subluxation with sudden reduction
CLASSIFICATION
Grading of PLC Injuries:
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Grade I: Mild instability (0–5 mm or 0–5°)
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Grade II: Moderate instability (6–10 mm or 6–10°)
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Grade III: Severe instability (>10 mm or >10°)
INVESTIGATIONS
Radiographs
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Segond fracture (lateral or medial)
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Arcuate sign (fibular styloid avulsion) – pathognomonic for PLC injury
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Gerdy’s tubercle avulsion
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Lateral joint space widening
MRI
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Grade I: Periligamentous T2 hyperintensity
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Grade II: Increased signal within an intact ligament
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Grade III: Complete ligament disruption with surrounding edema
TREATMENT
Non-operative Management
Indications: Grade I injuries or minimal functional impairment
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Hinged knee brace in extension for 6 weeks
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Gradual progression of range of motion and weight bearing
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Strengthening exercises
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Return to activity at approximately 3–4 months
OPERATIVE MANAGEMENT
Indications:
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Avulsion injuries
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Multiligament knee injuries
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Grade III PLC injuries
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Acute repair within 3–4 weeks is preferred.
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Fixation options include sutures, suture anchors, or bio-screws.
Surgical options include:
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PLC repair
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Hybrid PLC repair and reconstruction
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PLC reconstruction with or without ACL reconstruction, PCL reconstruction, and/or high tibial osteotomy (HTO)
PLC REPAIR
Indications:
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Isolated, acute Grade II PLC avulsion injuries
Limitations:
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Midsubstance repairs are associated with failure rates of approximately 40%
Techniques:
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Repair of the LCL, popliteus tendon, and/or popliteofibular ligament when anatomical reduction is achievable
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Reconstruction is recommended when reduction is not possible or tissue quality is poor
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Augmentation with a free graft may be used when repair is tenuous
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Fibular head avulsion fractures can be fixed using screws or suture anchors
HYBRID PLC RECONSTRUCTION AND REPAIR
Indications:
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Grade III midsubstance injuries
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Irreparable avulsion injuries
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Poor tissue quality
Techniques:
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Larson (fibular-based) reconstruction
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Trans-tibial double-bundle reconstruction
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LaPrade anatomic reconstruction
REHABILITATION
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Hinged knee brace with non-weight bearing for 6 weeks
Range of motion:
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Either immediate passive ROM (0–90°), or
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Immobilization for 2 weeks followed by gradual motion
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At 6 weeks: initiate weight bearing and closed-chain strengthening
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Return to sports and high-level activities at approximately 6–9 months
OUTCOMES
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Operative management yields superior outcomes compared to non-operative treatment
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Reconstruction demonstrates lower failure rates than repair
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Early intervention is associated with improved functional results
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Anatomic reconstruction restores rotational stability, although complete restoration of varus stability may not always be achieved
PLC RECONSTRUCTION ± ACL / PCL RECONSTRUCTION ± HTO
Indications:
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Acute or chronic combined ligament injuries
Principles:
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PLC reconstruction should be performed prior to or concurrently with ACL or PCL reconstruction to prevent early graft failure
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Valgus high tibial osteotomy is indicated in patients with varus mechanical alignment
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Failure to correct coronal plane malalignment significantly compromises reconstruction outcomes
Reconstruction techniques:
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Non-anatomic: Biceps tenodesis, iliotibial band sling, arcuate complex reconstruction
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Anatomic (preferred): LaPrade-style anatomic reconstruction or fibular-based Larson technique
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Key structures addressed include the LCL, popliteofibular ligament, and popliteus tendon
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The Larson technique is technically simpler and effective but may risk over-constraint if graft tensioning is not balanced
COMPLICATIONS
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Arthrofibrosis
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Missed PLC injury
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Failure to recognize PLC injury leading to ACL or PCL reconstruction failure
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Peroneal nerve injury (15–29%)
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