Posterior Cruciate Ligament (PCL) Injury

Overview

Snapshot

• A 22-year-old man presents to the emergency department after being involved in a motor vehicle accident. The patient is conscious but reports knee pain. He was wearing a seat belt, denies any head trauma, but says that his knees collided with the dashboard. Physical examination is significant for increased laxity of the proximal tibia with posterior force. A magnetic resonance imaging of the knee is consistent with a posterior cruciate ligament tear.

Introduction

• Clinical definition
  • injury of the posterior cruciate ligament (PCL)
• Epidemiology
  • risk factors
    • high-energy trauma (e.g., motor vehicle accident)
    • sport activities
• Etiology
  • trauma that posteriorly translates the proximal tibia
• Pathoanatomy 
  • normal anatomy
    • the largest intraarticular ligament in the knee
    • originates from the lateral portion of the medial femoral condyle and inserts at the fovea centralis (PCL facet)
  • pathology
    • posteriorly directed shear force when the knee is flexed
      • “dashboard injury” (high-energy trauma)
        • when the proximal tibia collides with the dashboard of a car in a motor vehicle accident
      • sports injuries (low-energy trauma)
        • the player falls on their knee while it is flexed and the foot is plantarflexed
        • direct trauma to the anterior knee 
• Associated conditions
  • high-energy trauma can result in PCL injury as well as injury to the
    • posterolateral corner
    • anterior cruciate ligament
    • medial collateral ligament
• Prognosis
• insufficient evidence to determine the true prognosis

Presentation

• Symptoms
  • may present with posterior knee pain
    • athletes may continue playing sports and not seek medical care
• Physical exam
  • posterior drawer test 
    • the proximal tibial is pushed posteriorly to assess for PCL laxity while the knee is flexed at 90 degrees
      • posterior translation is considered a positive test
  • mild-to-moderate effusion
  • slight limp or antalgic gait
• may have impaired terminal knee flexion

Imaging

• Radiography
  • indication
    • performed initially to assess for fractures
• Magnetic resonance imaging (MRI)
  • indication
    • typically performed in all patients presenting with acute PCL injury
• highly sensitive and accurate for acute PCL injury

Studies

• Making the diagnosis
  • a presumptive diagnosis can be made based on clinical presentation
• MRI can definitively diagnose acute or subacute PCL injury

Differential

• Anterior cruciate ligament injury 
  • distinguishing factor
    • patients typically hear a “pop” after injury and there is typically significant edema and joint effusion
• patients have a positive anterior drawer test

Treatment

• Conservative
  • rest, ice, compression, and elevation (RICE) therapy
    • indication
      • standard management of patients with an isolated PCL injury
        • in addition to RICE therapy, patients should receive
          • nonsteroidal anti-inflammatory drugs (NSAIDs) or acetaminophen for pain management
          • immobilization in extension (e.g., hinged knee brace)
• Operative
  • reconstructive surgery
    • indication
• typically reserved for acute and multi-ligamentous knee injuries

Complications

• May result in osteoarthritis