title: Shoe-surface friction influences movement strategies during a sidestep cutting task: implications for anterior cruciate ligament injury risk.
abstract: BACKGROUND
  Increasing the coefficient of friction of the shoe-surface interaction has been shown to lead to increased incidence of anterior cruciate ligament (ACL) injuries, but the causes for this increase are unknown. Previous studies indicate that specific biomechanical measures during landing are associated with an increased risk for ACL injury.
  
  
  OBJECTIVE
  At foot contact during a sidestep cutting task, subjects use different movement strategies for shoe-surface conditions with a high coefficient of friction (COF) relative to a low friction condition. Specifically, the study tested for significant differences in knee kinematics, external knee moments, and the position of the center of mass for different COFs.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Twenty-two healthy subjects (11 male) were evaluated performing a 30 degrees sidestep cutting task on a low friction surface (0.38) and a high friction surface (0.87) at a constant speed. An 8-camera markerless motion capture system combined with 2 force plates was used to measure full-body kinematics, kinetics, and center of mass.
  
  
  RESULTS
  At foot contact, subjects had a lower knee flexion angle (P = .01), lower external knee flexion moment (P < .001), higher external knee valgus moment (P < .001), and greater medial distance of the center of mass from the support limb (P < .001) on the high friction surface relative to the low friction surface.
  
  
  CONCLUSIONS
  The high COF shoe-surface condition was associated with biomechanical conditions that can increase the risk of ACL injury. The higher incidence of ACL injury observed on high friction surfaces could be a result of these biomechanical changes. The differences in the biomechanical variables were the result of an anticipated stimulus due to different surface friction, with other conditions remaining constant.
  
  
  CONCLUSIONS
  The risk analysis of ACL injury should consider the biomechanical movement changes that occur for a shoe-surface condition with high friction.
authors.affiliation: Department of Mechanical Engineering, Stanford University, Durand Building 061, Stanford, CA 94305-4308, USA. adowling@stanford.edu
authors.forename: Ariel V
authors.initials: AV
authors.lastname: Dowling
authors.forename: Stefano
authors.initials: S
authors.lastname: Corazza
authors.forename: Ajit M W
authors.initials: AM
authors.lastname: Chaudhari
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Andriacchi
mesh_terms: D000328:Adult; D000070598:Anterior Cruciate Ligament Injuries; D001696:Biomechanical Phenomena / Q000502:physiology; D005260:Female; D017276:Friction; D006801:Humans; D007593:Joint Instability; D007717:Knee / Q000502:physiology*; D007718:Knee Injuries / Q000517:prevention & control*; D008297:Male; D012307:Risk Factors; D012775:Shoes / Q000009:adverse effects*; D055815:Young Adult