Anterior cruciate ligament injury

Mechanism of injury

  • The ACL is responsible for restraint vs anterior/forward movement of the tibia
  • Injury: A sudden deceleration or change in direction on a fixed foot - for example, netball
  • 50% of ACL tears occur in association with a meniscal tear (usually lateral)

Clinical features

  • A sudden painful pop is felt
  • Rapid swelling - accumulation of a haemarthrosis within 2 hours of incident
  • Examination:
    • Positive Lachman test
    • Anterior draw test might be positive
    • Lateral knee tenderness

Investigations

  • MRI

Posterior cruciate ligament injury

Mechanism of injury

  • The PCL is responsible for restraint vs backwards/posterior movement of the tibia
  • Injury: A high energy, direct blow to the proximal tibia, whilst the knee is inflexion (e.g. RTC or contact sport injury)

Clinical features

  • Pain in the back of the knee
  • Examination: 
    • Positive posterior draw test
    • Posterior sag test may be positive 
    • Mild knee effusion/swelling can be present 

Meniscal tear

Mechanism of injury

  • Can be related to underlying degenerative process such as osteoarthritis. 
  • More acutely, can be torn whilst pivoting or twisting suddenly - often during sport

Clinical features

  • Knee pain - localised over the anteromedial or anterolateral joint line
  • Locking or clicking
  • Examination:
    • Effusion, tenderness as above
    • McMurray test may be positive

Medial collateral ligament injury

Mechanism of injury

  • A direct blow to the LATERAL aspect of the knee - for example during contact sport

Clinical features

  • Medial knee pain
  • Examination 
    • Pain along the course of the ligament
    • Positive valgus stress test

Lateral collateral ligament injury

Mechanism of injury

  • A direct blow to the MEDIAL aspect of the knee - for example during contact sport

Clinical features

  • Lateral knee pain
  • Examination 
    • Pain along the course of the ligament
    • Positive varus stress test 

Quadriceps tendon rupture / Patellar tendon rupture

Mechanism of injury

  • Usually following a fall/ during a sporting injury

Clinical features

  • Unable to perform straight leg raise
  • Unable to extend knee
  • Patella migration - away from the rupture (i.e. if patella tendon is ruptured, migrates proximally; but if quad tendon ruptured - distal migration).

Tibial plateau fracture

Mechanism of injury

  • Bumper injury or fall from height - fracture of tibial condyles 

Clinical features

  • Severe pain, swelling and extensive bruising

Investigations

  • CT