Avulsion fracture of ACL

Case contribution: Dr Radhiana Hassan


  • An 11 year old female
  • Trauma, electric scooter vs electric scooter
  • Complaint of pain and swelling over right knee
  • Unable to weight bear and unable to fully extend right knee
  • Clinical examination shows swollen right knee with limited ROM 30-90 degrees, generalized tenderness around knee region
  • Sensation intact, no foot drop

Radiograph of right knee in AP and lateral views:

  • bone fragment seen within the joint space
  • Associated irregularity seen at base of tibial eminence
  • No other fracture seen
  • No obvious soft tissue swelling
  • No radiopaque foreign body


MRI of right knee:

  • Sagittal T2-weighted images show the avulsion fracture (yellow arrows)
  • The avulsion fracture of tibial eminence is seen at the anterior intercondylar notch, at the attachment site of the ACL.
  • There is buckling of ACL with some heterogeneous signal and fluid seen at the anteromedial bundle.
  • However the continuity of the ligament is preserved.
  • There is also positive Blumeensaat angle.
  • The posterior cruciate ligament (PCL) is intact and normal.
  • No apparent PCL buckling is seen.

Intra-operative findings:

  • Avulsed fracture at base of tibial eminence
  • ACL substance intact
  • Fibrous tissue surrounding the fracture fragment removed
  • Medial and lateral meniscus intact
  • Arthroscopic and pull through suture right tibial eminence done

Diagnosis: Avulsion fracture of ACL (anterior cruciate ligament)


  • ACL avulsion fracture or tibial eminence avulsion fracture
  • It is seen as separation of the tibial attachment of the ACL to variable degrees’
  • Separation at femoral attachment is rare
  • It is more common in children than adult
  • There may be anterior translation of the femur on the tibia on lateral views
  • Classification (Meyers and McKeevers system)
    • Type 1: minimally/non-displaced fragment
    • Type 2: anterior elevation of the fragment
    • Type 3: complete separation of the fragment
      • 3a-involves small portion of the eminence
      • 3b-involves the majority of the eminence
  • Type 4: comminuted avulsion or rotation of the fracture fragment


Author: radhianahassan