Anterior

• Mechanism:

  • ACL is typically damaged due to:
  • Rapid changes in direction e.g. sudden deceleration, stopping, or change of direction with a fixed foot, or forceful hyperextension
• Symptoms:

  • A sudden, painful popping sensation or audible pop noise
  • Significant, rapid swelling (haemarthrosis) within one to two hours of injury
  • Inability to return to full activity
  • Instability of the knee joint - the tibia can move anteriorly below the femur - the knee can buckle and patients often feel a lack of confidence that the knee is stable
  • May occur in isolation or in combination with other internal knee injuries
  • Over time muscle weakness develops and there is an increased risk of other knee injuries e.g. meniscal tear
• Examination:

  • Lateral knee and joint line tenderness
  • Positive anterior draw test
  • Examination can be difficult shortly after the injury due to pain and swelling - more accurate after acute pain and swelling settled
• Anterior draw test:

  • Patient supine with knee flexed to 90 degrees and foot flat on couch
  • Rest forearm down patient's leg to fix position
  • Wrap hands behind upper tibia and place thumbs over tibial tuberosity
  • Pull tibia anteriorly
  • With healthy ACL should be little or no movement
  • Significant movement may suggest ACL damage
• When and how to refer:

  • Suspect fracture if meets Ottawa knee rules - A+E for XR
  • Suspect significant soft tissue injury if meets criteria - knee pain with trauma, popping sensation, knee giving way etc
  • Suspect that the soft tissue injury is an ACL injury based on history and examination findings
  • Would need review in line with local pathways - A+E, fracture clinic, acute knee clinic
• Investigations:

  • Imaging - MRI first line
  • Special - arthroscopy - to visualise cruciate ligament and diagnose tears
• Conservative management:

  • Rest, ice, compression and elevation
  • Analgesia - NSAIDs
  • Crutches and knee brace to help protect knee while mobilising
  • Physiotherapy
• Surgical management:

  • Arthroscopic surgery to reconstruct ligament is often required, especially in active young patients
  • Type and timing of surgery based on individual factors e.g. extent of ACL injury and patient baseline mobility
  • A new ligament is formed using a graft of tendon from another location