ACL Rupture

The cruciate ligaments are formed in-utero before the joint surfaces and are pivotal for normal knee function - excuse the pun!

Football is the commonest cause, but any injury with full weight over a twisted knee can cause an ACL rupture.



  • Significant valgus force
  • Significant twisting injury
  • Immediate pain +- "pop"
  • Immediate swelling with haemarthrosis


  • True knee joint swelling


  • Tenderness of the anteromedial corner


    • Normal laxity is 0
    • Grade 1: 0-0.5 cm of translation with an end point

(There may be no detectable opening in a Grade 1 injury)

    • Grade 2: 0.5-1.0 cm of translation with an end point
    • Grade 3: >1.0 cm of translation, usually there is no end point

Exclude combined ACL+ Meniscal Detachment

  • Joint line tenderness

Exclude combined ACL + MCL

Exclude combined ACL + PCL

Exclude combined ACL + PLC


AP and Lateral views

Exclude combination injuries

  • MCL: Joint Opening, Avulsion fractures
  • PCL: Joint Subluxation, Avulsion ractures
  • PLC: Joint Opening, Avlusions "Arcuate sign"
  • Osteohondral fracture: Lipo-haemarthrosis


  • For all multiple ligament injuries
  • Whenever a meniscal avulsion is suspected
  • For osteochondral fractures (lipo-haemarthrosis)

Emergency Room Treatment

Few of these patients will have multiligament injuries and will need an emergency orthopaedic referral. Please use the guidance on the referral form :-

Mr Gavin Holt :: :: Print this frame