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Mechanisms of ACL injury in professional rugby union: a systematic video analysis of 36 cases
  1. Connor Montgomery1,2,
  2. Jeff Blackburn3,
  3. Daniel Withers1,2,
  4. Gregory Tierney3,
  5. Cathal Moran1,2,
  6. Ciaran Simms3
  1. 1 Department of Orthopaedics and Sports Medicine, School of Medicine, Trinity College Dublin, Ireland
  2. 2 Sports Surgery Clinic, Santry, Dublin, Ireland
  3. 3 Centre for Bioengineering, School of Engineering, Trinity College Dublin, Dublin, Ireland
  1. Correspondence to Connor Montgomery, 14 Cadogan Park, Belfast, BT9 6HG, Northern Ireland, UK, montgodc{at}


Background The mechanisms of ACL injury in rugby are not well defined.

Aim To describe the mechanisms of ACL injury in male professional rugby players using systematic video analysis.

Methods 36 cases from games played in top professional leagues and international matches were analysed. 5 analysts independently assessed all videos to record the estimated frame/time of initial ground contact, frame/time of ACL tear and a range of play specific variables. This included contact versus non-contact ACL injuries, injury timing, joint flexion angles and foot contact with the ground. 37 side-stepping manoeuvres from a control game were analysed to allow comparison of non-injury versus injury situations.

Results 57% of ACL injuries occurred in a contact manner. 2 main scenarios were identified: (1) offensive running and (2) being tackled, indicating that the ball carrier might be at higher risk of ACL injury. The majority of non-contact ACL injuries resulted from a side-stepping manoeuvre. In most non-contact cases, initial ground contact was through heel strike. Statistical assessment of heel strike at initial ground contact versus non-heel strike cases showed a significant difference in injury versus non-injury outcomes, with heel strike associated with higher injury risk. Non-contact ACL injuries had lower median knee flexion angles and a more dorsiflexed ankle when compared with a control group (10° vs 20°, p≤0.001 and 10° vs 0°, p=0.033 respectively).

Conclusions Over half of ACL injuries in rugby in our analysis resulted from a contact mechanism. For non-contact injuries, lower knee flexion angles and heel-first ground contact in a side-stepping manoeuvre were associated with ACL injury.

  • ACL
  • Rugby
  • Anterior cruciate ligament
  • Knee injuries
  • Contact sports

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  • Contributors All authors were involved in the research concept and design, as well as data analysis and paper writing. CM, JB, GT and DW also performed the analysis.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement All data from our research has been discussed at least in part in the manuscript.