PLC Tear

PLC injuries typically result from high-energy forces or trauma to the knee. Common mechanisms include:

• A direct blow to the inside of the knee, causing outward (varus) stress
• Hyperextension of the knee
• Twisting injuries with the foot planted
• Sports-related contact injuries (football, soccer, skiing)
• Motor vehicle accidents or falls

Because of the forces involved, PLC injuries frequently occur alongside ACL or PCL tears.

The posterolateral corner is a complex region of the knee composed of several key stabilizing structures, including:

• Lateral collateral ligament (LCL)
• Popliteus tendon
• Popliteofibular ligament
• Joint capsule and supporting soft tissues

These structures work together to:

• Prevent excessive outward bending (varus)
• Control external rotation of the tibia
• Provide stability during walking, cutting, and pivoting movements

Damage to the PLC can result in rotational and lateral instability of the knee.

Symptoms vary based on the severity of injury and associated ligament damage and may include:

• Pain on the outside or back of the knee
• Swelling or stiffness
• A feeling of instability or the knee “giving way”
• Difficulty walking, especially on uneven surfaces
• Pain with pivoting or rotational movements
• In more severe cases, a sense that the knee is unstable even during routine activities

Neurologic symptoms such as numbness or weakness may occur if the peroneal nerve is affected.

Evaluation of a suspected posterolateral corner (PLC) injury requires careful assessment, as these injuries are complex and often occur with other ligament injuries.

Medical History

• How the injury occurred (direct blow, twisting injury, hyperextension, or trauma)
• Whether the injury involved contact or a high-energy mechanism
• The presence of instability or the knee “giving way,” especially during pivoting or walking on uneven surfaces
• Pain location, swelling, and stiffness
• Any difficulty walking or performing daily activities
• Symptoms of nerve involvement, such as numbness, tingling, or weakness in the lower leg or foot

Because PLC injuries commonly occur with ACL or PCL injuries, a detailed history helps guide further evaluation.

Physical Examination

The physical exam focuses on assessing knee stability and identifying associated injuries. This may include:

• Inspection for swelling, bruising, or abnormal knee alignment
• Palpation of the outside and back of the knee for tenderness
• Assessment of range of motion and strength
• Specific stress tests that evaluate outward bending (varus) and rotational stability of the knee
• Comparison with the uninjured knee to assess subtle instability
• Neurologic examination to assess the peroneal nerve, which runs near the PLC structures

Findings on exam help determine the severity of injury and whether multiple ligaments are involved.

Imaging

Imaging studies are often necessary to confirm the diagnosis and evaluate the full extent of injury:

• X-rays to rule out fractures, avulsion injuries, or abnormal joint alignment
• MRI to assess the PLC structures and identify associated ligament, cartilage, or meniscal injuries
• Stress radiographs may be used in certain cases to quantify instability

Accurate imaging is critical for treatment planning, especially when surgery is being considered.

Early treatment focuses on protecting the knee and reducing inflammation:

• Rest: Avoid activities that increase pain or instability
• Ice: Apply ice for 15–20 minutes several times daily
• Compression: Use an elastic wrap or knee brace
• Elevation: Elevate the leg to reduce swelling
• Pain control: Anti-inflammatory medications if appropriate
• Bracing: Hinged knee brace for added stability

Early evaluation by an orthopedic specialist is important due to the complexity of these injuries.