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Multiple risk factors related to familial predisposition to anterior cruciate ligament injury: fraternal twin sisters with anterior cruciate ligament ruptures
  1. T E Hewett1,2,3,
  2. T R Lynch4,
  3. G D Myer1,5,
  4. K R Ford1,3,
  5. R C Gwin4,
  6. R S Heidt Jr4
  1. 1Cincinnati Children's Hospital Medical Center and Research Foundation, Sports Medicine Biodynamics Center and Human Performance Laboratory, Cincinnati, Ohio, USA
  2. 2University of Cincinnati, College of Allied Health Sciences, Rehabilitation Sciences, Cincinnati, Ohio, USA
  3. 3University of Cincinnati Department of Pediatrics and Orthopaedic Surgery, College of Medicine, Rehabilitation Sciences and Department of Biomedical Engineering, College of Engineering, Cincinnati, Ohio, USA
  4. 4Wellington Orthopaedic and Sports Medicine, Cincinnati, Ohio, USA
  5. 5Rocky Mountain University of Health Professions, Provo, Utah, USA
  1. Correspondence to T E Hewett, Cincinnati Children's Hospital, 3333 Burnet Avenue; MLC 10001, Cincinnati, Ohio 45229, USA; tim.hewett{at}


Objective A multifactorial combination of predictors may increase anterior cruciate ligament (ACL) injury risk in athletes. The objective of this twin study was to examine these risk factors to identify commonalities in risk factors that predisposed female fraternal twins to ACL injury.

Methods Female twins in high-risk sports were prospectively measured prior to an injury for neuromuscular control using three-dimensional motion analysis during landing, hamstrings and quadriceps muscular strength on a dynamometer and joint laxity using a modified Beighton–Horan index and a Compu-KT arthrometer. Intraoperative measures of femoral intercondylar notch width were recorded during ACL reconstruction.

Results Abduction angles were increased at one knee in both of the twin sister athletes relative to uninjured controls at initial contact and at maximum displacement during landing. The twin female athletes that went on to ACL injury also demonstrated decreased peak knee flexion motion at both knees than uninjured females during landing. The twin athletes also had increased joint laxity and decreased hamstrings to quadriceps (H/Q) torque ratios compared to controls. Femoral intercondylar notch widths were also below the control mean in the twin siblings.

Conclusions Prescreened mature female twins that subsequently experienced ACL injury demonstrated multiple potential risk factors including: increased knee abduction angles, decreased knee flexion angles, increased general joint laxity, decreased H/Q ratios and femoral intercondylar notch width.

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  • Funding The authors would like to acknowledge funding support from National Institutes of Health Grant R01-AR049735 and R01 -AR055563.

  • Competing interests None.

  • Ethics approval Ethics approval was granted by the Cincinnati Children's Hospital Medical Center.

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