title: Multiple risk factors related to familial predisposition to anterior cruciate ligament injury: fraternal twin sisters with anterior cruciate ligament ruptures.
abstract: 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.
authors.affiliation: Cincinnati Children's Hospital Medical Center and Research Foundation, Sports Medicine Biodynamics Center and Human Performance Laboratory, Cincinnati, Ohio 45229, USA. tim.hewett@cchmc.org
authors.forename: T E
authors.initials: TE
authors.lastname: Hewett
authors.forename: T R
authors.initials: TR
authors.lastname: Lynch
authors.forename: G D
authors.initials: GD
authors.lastname: Myer
authors.forename: K R
authors.initials: KR
authors.lastname: Ford
authors.forename: R C
authors.initials: RC
authors.lastname: Gwin
authors.forename: R S
authors.initials: RS
authors.lastname: Heidt
mesh_terms: D000293:Adolescent; D000070598:Anterior Cruciate Ligament Injuries; D001490:Basketball / Q000293:injuries*; D001696:Biomechanical Phenomena / Q000502:physiology; D005260:Female; D020022:Genetic Predisposition to Disease / Q000235:genetics*; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology; D007719:Knee Joint / Q000502:physiology; D008124:Locomotion / Q000502:physiology; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology; D012307:Risk Factors; D012421:Rupture / Q000235:genetics; D012916:Soccer / Q000293:injuries*; D013647:Task Performance and Analysis; D014427:Twins; D014429:Twins, Dizygotic / Q000235:genetics*