Posterolateral Corner

Posterolateral Corner Injury

Article by John Miller

What is a Posterolateral Corner Injury?

Injuries to the posterolateral corner of the knee (PLC for short) are most commonly associated with athletic traumas, motor vehicle accidents and falls. PLC injuries account for 16% of all knee ligament injuries and often occur in combination with other cruciate ligament injuries.

PLC provides both static and dynamic stabilisation to the knee joint. The static structures include the lateral collateral ligament (LCL or FCL), popliteus tendon, the popliteofibular ligament and the posterolateral capsule. Together these structures prevent varus collapse at the knee and external rotation of the tibia on the femur. Dynamic structures of the PLC play similar roles as the static structures but through movement. These structures include the popliteus muscle, iliotibial band, bicep femoris and the lateral gastroc tendon.

Your PLC is the outside of your knee that extends from the bottom of your femur (thigh bone) to the heads of your tibia & fibula (lower leg bones).

Ligaments and joint capsules surrounding the joint provide stability during movement and weight-bearing.

Importantly, the common peroneal nerve (a nerve that supplies the lower leg and toes) wraps around the top of the fibula. It can become compromised if there is an injury to the PLC of the knee.

What Causes a Posterolateral Corner Injury?

A combined hyperextension and varus force to the knee can injure the posterolateral corner of the knee. An example of this could be a blow to the inside of your knee with a straight knee.

Other mechanisms include coupled hyperextension and external rotation of the tibia or external rotation of the tibia and a large varus force.

What are the Symptoms of a Posterolateral Corner Injury?

Injuries affecting the PLC may or may not occur in conjunction with injuries to other structures in the knee. Symptoms of a PLC injury commonly include:

  • Pain or swelling over the posterolateral surface of the knee.
  • Pain is aggravated by weight-bearing activities, especially high loads going through the lower limb, such as walking up a hill, quick direction changes or jumping.
  • Feeling of weakness or ‘giving way’ around the knee.

If you have an injury to the PLC and the peroneal nerve is affected, you may also experience pins and needles or numbness in the lower leg and foot. You may also experience foot or ankle weakness.

How is a Posterolateral Corner Injury Diagnosed?

On examination, your physiotherapist or sports doctor will look for signs of a PLC injury. Palpation and a series of knee ligament stability tests on physical examination confirm or deny damage to the PLC. They will be graded accordingly based on severity. An MRI may be required to confirm the diagnosis.

What is the Treatment for a Posterolateral Corner Injury?


Most patients with a mild posterolateral injury start to recover within a few weeks of the damage with the appropriate rehabilitation.

Your physiotherapy treatment will aim to:

  1. Reduce pain and inflammation
  2. Normalise joint range of motion
  3. Strengthen the muscles of your lower limb
  4. Improve patellofemoral (knee cap) alignment
  5. Normalise your muscle lengths
  6. Improve your proprioception, agility and balance
  7. Improve your technique and function with walking, running, squatting, hopping and landing
  8. Minimise your chance of reinjury

We advise that you discuss your knee injury with a knee injury practitioner such as a sports physiotherapist, sports physician or knee surgeon. Twill provide you with the most accurate information regarding your specific injury and rehabilitation program.


Most grade I PLC injuries resolve entirely with conservative treatment. In severe cases, depending on the number of structures within the PLC involved, surgery may be required. Risks of surgery include infection, persistent instability and pain, stiffness, and difficulty returning to the previous activity level. Operations are determined case by case and severity of the injury.

Functional instability is a problem with PLC injuries. Your sports physiotherapist, sports doctor or knee surgeon should professionally guide your return to sport.

Post-Surgical Rehabilitation

Post-operative knee rehabilitation is one of the most important yet too often neglected aspects of knee surgery. The most successful and quickest outcomes result from the guidance and supervision of an experienced physiotherapist.

Your rehabilitation following knee surgery focuses on restoring full knee motion, strength, power and endurance. You will also require individualised balance, proprioception and agility retraining towards your specific sporting or functional needs.

Your physiotherapist has extensive knowledge in this field. We suggest you contact them for the best advice in your circumstances.

How to Prevent a Posterolateral Corner Injury?

There are several things you can do to reduce your risk of sustaining a PLC injury.

These include:

  • Correcting poor biomechanics of the knee or ankle joints
  • Adequate warm-up and stretching program before and after exercise
  • Correcting muscle imbalances in the lower limb
  • Adequate footwear during exercise
  • Avoid sudden increases in training frequency or intensity.
  • Strengthening muscles of the lower limb

Return to Sports with a Posterolateral Corner Injury

An inadequate rehabilitation regime often renders the athlete to experience difficulty when returning to their sport after sustaining a PLC injury. It is crucial to complete your specialised rehabilitation program as prescribed by your physiotherapist to enable a return to competition as quickly and safely as possible.

Common Causes - Knee Pain

Knee pain can have many origins from local injury, referred pain, biomechanical issues and systemic issues. While knee pain can appear simple to the untrained eye, a thorough assessment is often required to ascertain the origin of your symptoms. The good news is that once a definitive diagnosis is determined, most knee pain quickly resolves with the correct treatment and rehabilitation.

Knee Ligament Injuries

Knee Meniscus Injuries

Kneecap Pain

Knee Arthritis

Knee Tendon Injuries

Muscle Injuries

Knee Bursitis

Children’s Knee Conditions

Other Knee-Related Conditions

Knee Surgery

Knee FAQs

For specific information regarding your knee pain, please seek the assistance of a healthcare professional with a particular interest in knee condition, such as your knee physiotherapist.

Acute Injury Signs

Acute Injury Management.

Here are some warning signs that you have an injury. While some injuries are immediately evident, others can creep up slowly and progressively get worse. If you don't pay attention to both types of injuries, chronic problems can develop.

For detailed information on specific injuries, check out the injury by body part section.

Don't Ignore these Injury Warning Signs

Joint Pain

Joint pain, particularly in the knee, ankle, elbow, and wrist joints, should never be ignored. Because these joints are not covered by muscle, pain here is rarely of muscular origin. Joint pain that lasts more than 48 hours requires a professional diagnosis.


If you can elicit pain at a specific point in a bone, muscle, or joint, you may have a significant injury by pressing your finger into it. If the same spot on the other side of the body does not produce the same pain, you should probably see your health professional.  


Nearly all sports or musculoskeletal injuries cause swelling. Swelling is usually quite obvious and can be seen, but occasionally you may feel as though something is swollen or "full" even though it looks normal. Swelling usually goes along with pain, redness and heat.

Reduced Range of Motion

If the swelling isn't obvious, you can usually find it by checking for a reduced range of motion in a joint. If there is significant swelling within a joint, you will lose range of motion. Compare one side of the body with the other to identify major differences. If there are any, you probably have an injury that needs attention.


Compare sides for weakness by performing the same task. One way to tell is to lift the same weight with the right and left sides and look at the result. Or try to place body weight on one leg and then the other. A difference in your ability to support your weight is another suggestion of an injury that requires attention.

Immediate Injury Treatment: Step-by-Step Guidelines

  • Stop the activity immediately.
  • Wrap the injured part in a compression bandage.
  • Apply ice to the injured part (use a bag of crushed ice or a bag of frozen vegetables).
  • Elevate the injured part to reduce swelling.
  • Consult your health practitioner for a proper diagnosis of any serious injury.
  • Rehabilitate your injury under professional guidance.
  • Seek a second opinion if you are not improving.