What Is a Posterolateral Corner Injury?

The posterolateral corner (PLC) is a complex group of ligaments, tendons, and soft tissue that keep your knee stable when you rotate, twist or bear weight. A posterolateral corner injury compromises this support. You may lose control during certain movements, feel pain or experience knee instability, especially when your leg is fully extended.

Research shows that posterolateral corner injuries make up about 16% of all knee ligament injuries, though isolated cases are uncommon. In one MRI-based study of 187 ligament injuries, only 2.1% had isolated PLC tears, while 87% of PLC injuries involved multiple ligaments.

Anatomy of the PLC

The PLC includes three key stabilizers:

• Lateral (fibular) collateral ligament (LCL): Prevents the knee from bowing outward under pressure (varus stress).
• Popliteus tendon: Helps resist external tibial rotation and stabilizes your knee as it bends.
• Popliteofibular ligament: Provides support during twisting motions, especially when your knee is flexed.

Several secondary structures also contribute:

• Arcuate ligament
• Fabellofibular ligament
• Biceps femoris tendon
• Lateral capsule
• Iliotibial band

Together, these structures control knee motion, reduce strain on other ligaments and protect against abnormal rotation or shifting.

Causes of PLC Injuries

You might develop a PLC injury after:

• A direct hit to the anteromedial side of the knee (like in a dashboard injury)
• Hyperextension during activity or a fall
• A varus force, when the knee bends outward under pressure
• A twisting injury with external rotation
• A knee dislocation during high-impact trauma

These injuries often involve more than one structure. For example, 62% of people with posterior cruciate ligament (PCL) tears also have PLC damage.

Symptoms of PLC Injuries

You may notice pain or instability near the outside or back of your knee. Common symptoms include:

• Difficulty walking, especially on uneven ground or stairs
• Feeling like your knee gives out during weight-bearing
• A varus thrust gait, where your knee bows outward as you step
• Bruising, swelling or tenderness after injury
• Numbness or foot drop, which may signal common peroneal nerve damage (occurs in up to 30% of cases)

These symptoms may worsen if you also have a cruciate ligament tear.

Diagnosis of PLC Injuries

The orthopaedic sports medicine specialists at University Orthopaedic Associates will examine your knee carefully to look for signs of instability or ligament damage.

Key tests may include:

• Varus stress test: Tests at 0 and 30 degrees to measure gapping on the outer knee
• Dial test: Checks for increased external tibial rotation
• Reverse pivot shift test: Detects instability when moving from a flexed to an extended knee
• Posterolateral drawer test: Measures translation during combined rotation and posterior force

MRI is critical. It helps confirm injuries to the LCL, popliteus and popliteofibular ligament. You may also see bone bruising or small avulsion fractures near the fibula.

In chronic injuries, long-leg standing X-rays can reveal varus alignment, which affects how the knee bears weight and may require surgical correction.

Treatment Options

Treatment depends on the severity of your posterolateral corner injury.

Non-Operative Care

Grade I or mild grade II injuries may heal without surgery. You may need:

• A hinged knee brace locked in full extension for 4 weeks
• A gradual rehab program focused on quad strengthening
• Return to sport in 6 to 8 weeks

Surgical Treatment

Grade III injuries, or any injury involving full tears or tissue damage, typically require surgery.

Options include:

• Primary repair for acute avulsion injuries, if the torn ligament can be reattached
• Reconstruction using tendon grafts (semitendinosus, Achilles, etc.) to restore the LCL and popliteofibular ligament
• Hybrid repair with reinforcement using a graft
• LaPrade anatomic reconstruction, which rebuilds the PLC using two grafts placed in anatomical positions

If your knee has chronic varus deformity, your surgeon may recommend a proximal tibial osteotomy to realign the leg before reconstructing the PLC.

What to Expect During Recovery

Recovery depends on the type of treatment. With bracing and rehab, mild injuries can heal within two months. If you undergo reconstruction, the timeline may extend to six months or more, depending on rehab progress and graft healing.

Skipping or delaying treatment increases the risk of graft failure after ACL or PCL surgery. You may also face long-term issues like arthritis, especially with untreated posterolateral corner injuries.

Regain Knee Stability With Help From UOA

If you are dealing with knee instability, unexplained pain or a recent injury, the orthopaedic sports medicine specialists at University Orthopaedic Associates can help. Our team uses advanced diagnostic tools and personalized treatment strategies to repair posterolateral corner injuries and restore your mobility.

Schedule a consultation today with a UOA physician to explore your treatment options and get back to moving with confidence.