ACL Injury

• ACL attachment points:

  • Anterior aspect of intercondylar area of tibia
  • Posterior aspect of intercondylar area of femur

  
• Non-contact ACL injuries:

  • caused by rotation/valgus force with fixed foot most common
• Contact ACL injuries:

  • Direct blow with valgus collapse (more likely to injure more than one structure)
• ACL injuries:

  • 72% non contact, 28 % contact (Boden et al 2000)
  • 70% occur in athletic populations (Griffin et al 2000)
  • Up to 15% of elite athletes and 3% of amateur athletes
• Higher incidence of ACL tear in females:

  • anatomical variations - increase risk of ACL tears
  • hormonal factors - different stages of the menstrual cycle can leads to greater ligamentous laxity (looseness)
  • neuromuscular factors - Interplay between neural and muscular systems in providing dynamic stability to a joint. Greater flexibility of hamstring decreases some passive protection of ACL
• ACL typical presentation:

  • Audible Snap or Pop
  • Immediate Pain
  • Haemarthrosis within 2 hrs
  • Difficulty Walking / Running
  • Instability/ giving way
• ACL diagnosis

  • Ligament stress tests
  • Positive test: increased laxity and soft end feel
  • Suprapatellar swelling
• Joint effusion:

  • Fluid in supra-patella pouch = Intra-articular injury
  • More vascularity = More/earlier swelling
  • Blood/fat in fluid = Bony injury
• Assessing swelling:

  • Large effusions can be easily visible
  • Can also use:
  • Patella tap - good for medium effusions
  • Patella sweep – better for small effusions
• Ligamentous stability:

  • as well as limiting valgus and internal rotation, ACL prevents anterior tibial translation from the femur, which is used in deceleration movement e.g. going down stairs

  
• Ligamentous stability - special tests:

  • as well as limiting valgus and internal rotation, ACL prevents anterior tibial translation from the femur, which is used in deceleration movement e.g. going down stairs
  • so applying anterior force to tibia relative to femur can replicate a stress test
  • positive test: increased laxity and soft end feel
• Ligamentous stability - special tests:

  • Anterior drawer test
  • Lachmans test
  • positive test would be shown by increased laxity and soft end feel
• ACL reconstruction:

  • graft taken, commonly from hamstring tendon, and built through tibial tuberosity and fixed onto femur
  • another way is have a section of the patella removed with bony attachments either side

  
• Ligament Avulsion:

  • Can have ACL repair instead of ACL reconstruction if caught early
  • Indication for early x-ray if suspicious