title: Calculation of external knee adduction moments: a comparison of an inverse dynamics approach and a simplified lever-arm approach.
abstract: BACKGROUND
  The external knee adduction moment (EKAM) is often studied in knee osteoarthritis research. This study compared EKAMs between two methods of calculation: a method that only requires ground reaction force and knee position data (i.e. lever-arm), and an inverse dynamics link-segment method.
  
  
  METHODS
  Sixteen participants walked while wearing a control shoe with and without a six millimeter lateral wedge insole. Peak EKAMs between the lever-arm and inverse dynamics methods were compared for the control condition, and the %change in moment induced by the lateral wedge was compared between methods.
  
  
  RESULTS
  When comparing EKAMs between methods, no correlation was found (r=0.24, p=0.36); peak EKAMs with the lever-arm method (26.0Nm) were significantly lower than EKAMs with the inverse dynamics method (40.2Nm, pb0.001); and Bland-Altman plots showed poor agreement between methods. When assessing the %change in moment with a lateral wedge, a moderate correlation was found (r=0.55, p=0.03) between methods; Bland-Altman plots showed moderate agreement between methods; and the lever-arm method (-6.4%) was not significantly different from the inverse dynamics method (-11.4%, p=0.09); however, the two methods produced opposite results 31% of the time.
  
  
  CONCLUSIONS
  The lever-arm method cannot estimate peak EKAMs, and can only approximate the %change in moment induced by a lateral wedge; however, the error rate was 31%. Therefore, the lever-arm method is not recommended for use in its current form.
  
  
  CONCLUSIONS
  This study may help guide the development of a fast and simple method for determining EKAMs for individuals with knee osteoarthritis.
authors.affiliation: Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada; Biomedical Engineering, Schulich School of Engineering, University of Calgary, Calgary, AB, Canada; Faculty of Medicine, University of Calgary, Calgary, AB, Canada. Electronic address: lewinson@ucalgary.ca.
authors.forename: Ryan T
authors.initials: RT
authors.lastname: Lewinson
authors.affiliation: Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada.
authors.forename: Jay T
authors.initials: JT
authors.lastname: Worobets
authors.affiliation: Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada; Biomedical Engineering, Schulich School of Engineering, University of Calgary, Calgary, AB, Canada.
authors.forename: Darren J
authors.initials: DJ
authors.lastname: Stefanyshyn
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D009989:Orthotic Devices; D020370:Osteoarthritis, Knee / Q000175:diagnosis / Q000503:physiopathology* / Q000628:therapy; D016059:Range of Motion, Articular / Q000502:physiology*; D016138:Walking / Q000502:physiology*; D055815:Young Adult
keywords: Gait; Insoles; Joint loading; Osteoarthritis