Posterior

• Mechanism of injury:

  • Typically a direct blow to the proximal tibia with the knee in flexion, or a hyperextension injury
  • Usually there is a history of high energy trauma such as a road traffic accident (dashboard injury) or sports injury
• Symptoms:

  • If only the PCL is injured the person may be relatively asymptomatic immediately after the injury
  • There may be posterior pain or pain on kneeling
  • May occur in isolation or in combination with other internal knee injuries
  • Commonly associated with posterolateral corner injury
• Posterolateral corner injury:

  • Commonly result from a force directed at the anteromedial aspect of the knee
  • Posterolateral corner is a complex area of tendons and ligaments
  • Meeting point of the lateral collateral ligaments, popliteofibular ligament, popliteus tendon, iliotibial band and more
  • Resists varus force and hyperextension of the knee
• Signs:

  • Mild effusion and reduced range of knee flexion may be present
  • Posterior draw test will often be positive
  • Posterior sag test may be positive
• Posterior sag test:

  • PCL prevents backward displacement of tibia - if its damaged the tibia can sag
  • Ask patient to flex knee to 90 degrees with foot flat on bed and inspect from the side to see if tibia sags posteriorly
• Posterior draw test:

  • Same positioning as the anterior draw test
  • Push tibia posteriorly
  • Posterior movement suggests PCL damage