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The anterior cruciate ligament injury controversy: is “valgus collapse” a sex-specific mechanism?
  1. C E Quatman1,2,
  2. T E Hewett1,3,4
  1. 1
    Cincinnati Children’s Hospital Research Foundation Sports Medicine Biodynamics Center and Human Performance Laboratory, Cincinnati, Ohio, USA
  2. 2
    University of Toledo, Engineering Center for Orthopaedic Research Excellence, Toledo, Ohio, USA
  3. 3
    Cincinnati Children’s Hospital Research Foundation, Division of Molecular Cardiovascular Biology Cincinnati, Ohio, USA
  4. 4
    University of Cincinnati College of Medicine, Departments of Pediatrics, Orthopaedic, Surgery Biomedical Engineering, and Department of Rehabilitation Sciences, College of Allied Health Sciences, Cincinnati, Ohio, USA
  1. Dr T E Hewett, Cincinnati Children’s Hospital, 3333 Burnet Avenue; MLC 10001, Cincinnati, OH 45229, USA; tim.hewett{at}


Background: Anterior cruciate ligament (ACL) injury is a devastating injury that puts an athlete at high risk of future osteoarthritis. Identification of risk factors and development of ACL prevention programmes likely decrease injury risk. Although studies indicate that sagittal plane biomechanical factors contribute to ACL loading mechanisms, it is unlikely that non-contact ACL injuries occur solely in a sagittal plane. Some authors attempt to ascribe the solely sagittal plane injury mechanism to both female and male ACL injuries and rebuff the concept that knee “valgus” is associated with isolated ACL injury. Prospective studies that utilise coupled biomechanical and epidemiological approaches demonstrated that frontal knee motions and torques are strong predictors of future non-contact ACL injury risk in female athletes. Video analysis studies also indicate a frontal plane “valgus collapse” mechanism of injury in women. As load sharing between knee ligaments is complex, frontal as well as sagittal and transverse plane loading mechanisms likely contribute to non-contact ACL injury. The purpose of this review is to summarise existing evidence regarding ACL injury mechanisms and to propose that sex-specific mechanisms of ACL injury may occur, with women sustaining injuries by a predominantly “valgus collapse” mechanism.

Conclusion: Prevention programmes and interventions that only target high-risk sagittal plane landing mechanics, especially in the female athlete, are likely to be less effective in ameliorating important frontal and transverse plane contributions to ACL injury mechanisms and could seriously hamper ACL injury prevention efforts. Programmes that target the reduction of high-risk valgus and sagittal plane movements will probably prove to be superior for ACL injury prevention.

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  • Competing interests: None.

  • Funding: The authors would like to acknowledge funding support from the University of Toledo College of Medicine Pre-Doctoral Fellowship and the Plus One Active Research Grant on Wellness Using Internet Technology from the American College of Sports Medicine Foundation (CEQ). This work was also partly supported by National Institutes of Health grants R01-AR049735 and R01-AR055563 (TEH) and R01-AR056259 (CEQ and TEH).

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