What is the management for a patient with a magnetic resonance imaging (MRI)-confirmed posterolateral corner (PLC) injury of the knee?

MRI Findings and Management of Posterolateral Corner (PLC) Knee Injuries

Direct Answer to MRI Detection

MRI is essential for detecting PLC injuries because these injuries occur in 19.7% of ACL cases and, if missed, lead to considerable morbidity and failed cruciate ligament reconstructions. 1

Why MRI Matters for PLC Injuries

• MRI identifies concomitant PLC injuries that are frequently missed on clinical examination alone, particularly when they occur alongside cruciate ligament tears 1
• Both 1.5T and 3T MRI protocols provide equivalent diagnostic accuracy for detecting PLC injuries, so routine 3T imaging offers no significant advantage 1, 2
• Timing is critical: obtain MRI within 6 weeks of acute trauma because some PLC injuries resolve or become less visible with chronicity 1, 2
• Lateral bone contusions visible on MRI correlate with high-grade pivot-shift injuries and predict concomitant PLC damage 1

Key MRI Findings Indicating PLC Injury

• Look for disruption of the lateral collateral ligament, popliteus muscle-tendon unit, and popliteofibular ligament—the three primary PLC structures 3
• Bone marrow edema patterns in the lateral tibial plateau and lateral femoral condyle suggest PLC injury mechanism 4, 1
• Always evaluate for associated cruciate ligament tears, as isolated PLC injuries are uncommon; most occur with ACL or PCL ruptures 5, 3

Management Algorithm Based on MRI Findings

Acute Isolated PLC Injuries (Grade I-II)

• Non-operative management with bracing and rehabilitation can be attempted for partial tears 6
• However, complete PLC lesions rarely heal with conservative treatment alone 6

Acute Complete PLC Injuries (Grade III)

• Primary surgical reconstruction is superior to repair, with reconstruction showing only 9% failure rate compared to 37% failure rate with repair 7
• The modified 2-tailed anatomical reconstruction technique targeting the anatomical locations of the popliteus tendon, fibular collateral ligament, and popliteofibular ligament is the preferred approach 8, 7
• Early motion rehabilitation protocols combined with reconstruction yield better outcomes than repair 7

Chronic PLC Injuries

• Anatomical reconstruction using 2-graft technique is the treatment of choice, showing significant improvements in Lysholm, IKDC, and Tegner scores at 40.9-month follow-up 8
• Varus stress radiographs should be obtained to objectively quantify lateral compartment opening and guide surgical planning 8, 6

Combined PLC and Cruciate Ligament Injuries

• Failure to recognize and address PLC injury results in continued knee instability and cruciate ligament reconstruction failure 5, 3
• Both injuries must be reconstructed—ignoring the PLC component leads to poor outcomes 5
• Clinical outcomes for combined injuries are similar to isolated PLC injuries when both are properly addressed 8

Critical Pitfalls to Avoid

• Never proceed with isolated cruciate ligament reconstruction when MRI shows PLC injury—this guarantees reconstruction failure 5, 3
• Do not delay MRI beyond 6 weeks if PLC injury is suspected, as visualization becomes more difficult 1, 2
• Do not rely on clinical examination alone—PLC injuries are frequently occult and require MRI confirmation 6
• Do not attempt primary repair for high-energy PLC injuries—reconstruction has significantly lower failure rates (9% vs 37%) 7
• Always obtain initial radiographs before MRI to exclude fractures and bony avulsions, particularly in patients under 40 years 1, 2

Surgical Revision for Failed Primary Treatment

• Fourteen of 15 patients with failed primary PLC repair or reconstruction achieved successful outcomes with revision anatomical reconstruction 7
• This underscores that even failed initial treatment can be salvaged with proper anatomical reconstruction technique 7