Posterolateral Corner (PLC) Injury
What ss the Anatomy and Function of the PLC?
The posterolateral corner (PLC) of the knee is a complex group of structures located on the outer (lateral) and back (posterior) side of the knee. These structures work together to stabilize the knee against varus (inward) forces and external rotation.
The key components of the PLC include:
Lateral collateral ligament (LCL) – resists varus stress (outward bending).
Popliteus tendon and popliteofibular ligament – control external rotation and posterolateral stability.
Lateral capsule, arcuate ligament complex, and biceps femoris tendon – provide additional dynamic and static stability.
The PLC functions in coordination with the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), and medial collateral ligament (MCL) to maintain overall knee stability, particularly during pivoting, deceleration, and direction changes.
How Do PLC Injuries Occur?
PLC injuries typically result from high-energy trauma or a forceful twisting mechanism. Common causes include:
A direct blow to the inside (medial) of the knee while the leg is slightly bent — forcing the knee outward (varus) and rotating it externally.
Sports injuries involving cutting and pivoting (e.g., football, skiing, rugby).
Motor vehicle accidents, especially when combined with knee dislocations.
PLC injuries often occur in combination with ACL or PCL tears due to the shared stabilizing role of these structures.
What Other Concomitant Injuries Occur with a PLC Injury?
Isolated PLC injuries are uncommon. The posterolateral corner is usually injured along with other major ligaments, particularly in high-energy trauma. Common associated injuries include:
PCL tears (most common ligament combination)
ACL tears
Meniscal tears
Cartilage injuries
Common peroneal nerve injury: leading to numbness and weakness in foot dorsiflexion (“foot drop”). This injury can lead to long-term disability
Identifying all associated injuries is essential, as missed PLC instability can cause failure of ACL or PCL reconstructions.
How Do You Diagnose a PLC Injury?
Diagnosis relies on a combination of clinical examination, imaging, and the mechanism of injury.
Clinical Assessment:
History: Patients often describe pain and swelling along the outer side of the knee after a twisting or high-energy injury.
Symptoms: Instability and a feeling of the knee “giving way.”
Physical examination tests:
Varus stress instability
Excessive external rotation compared to the non-injured knee
Nerovascular assessment to rule out common peroneal nerve injury or popliteal artery injury
Physical examination tests:
Varus stress instability
Excessive external rotation compared to the non-injured knee
Imaging:
o MRI scan – the gold standard for visualizing soft tissue injuries to the PLC but can often be missed with older injuries
o X-rays – may show widening of the lateral joint space or avulsion fractures from the fibular head
What are the Indications for Conservative Management of PLC Injuries?
Non-surgical management may be appropriate for low-grade or isolated PLC injuries where the knee remains stable and alignment is preserved.
Indications include:
Mild sprain/injuries
Isolated PLC injury without cruciate ligament involvement
Minimal varus or rotational instability on stress testing
Low-demand patients or those unable to undergo surgery
Conservative treatment typically involves:
Use of a hinged knee brace for 4–6 weeks to protect healing tissues
Physiotherapy to restore strength, balance, and proprioception
Gradual return to activity over 3–4 months
What are the Indications for Surgical Management of PLC Injuries?
Surgical intervention is recommended for high-grade PLC tears and those with associated multi-ligament injuries to restore normal knee function and prevent long-term instability.
Other indications include:
Knee dislocations
Persistent varus or rotational instability after conservative management
Avulsion injuries (ligament pulled off bone) that cannot heal properly without fixation
High-demand or athletic patients requiring full stability for return to sport
Surgical treatment may involve anatomic reconstruction of the LCL, popliteus tendon and popliteofibular ligament using tendon grafts. Repairs can occur with avulsion injuries.
MELBOURNE ORTHOPAEDIC SURGERY