title: The association between knee joint biomechanics and neuromuscular control and moderate knee osteoarthritis radiographic and pain severity.
abstract: OBJECTIVE
  The objective of this study was to determine the association between biomechanical and neuromuscular factors of clinically diagnosed mild to moderate knee osteoarthritis (OA) with radiographic severity and pain severity separately.
  
  
  METHODS
  Three-dimensional gait analysis and electromyography were performed on a group of 40 participants with clinically diagnosed mild to moderate medial knee OA. Associations between radiographic severity, defined using a visual analog radiographic score, and pain severity, defined with the pain subscale of the WOMAC osteoarthritis index, with knee joint kinematics and kinetics, electromyography patterns of periarticular knee muscles, BMI and gait speed were determined with correlation analyses. Multiple linear regression analyses of radiographic and pain severity were also explored.
  
  
  RESULTS
  Statistically significant correlations between radiographic severity and the overall magnitude of the knee adduction moment during stance (r²=21.4%, P=0.003) and the magnitude of the knee flexion angle during the gait cycle (r²=11.4%, P=0.03) were found. Significant correlations between pain and gait speed (r²=28.2%, P<0.0001), the activation patterns of the lateral gastrocnemius (r²=16.6%, P=0.009) and the medial hamstring (r²=10.3%, P=0.04) during gait were found. The combination of the magnitude of the knee adduction moment during stance and BMI explained a significant portion of the variability in radiographic severity (R(2)=27.1%, P<0.0001). No multivariate model explained pain severity better than gait speed alone.
  
  
  CONCLUSIONS
  This study suggests that some knee joint biomechanical variables are associated with structural knee OA severity measured from radiographs in clinically diagnosed mild to moderate levels of disease, but that pain severity is only reflected in gait speed and neuromuscular activation patterns. A combination of the knee adduction moment and BMI better explained structural knee OA severity than any individual factor alone.
authors.affiliation: Dalhousie University, School of Biomedical Engineering, Halifax, NS, Canada. Janie.Astephen@Dal.ca
authors.forename: J L
authors.initials: JL
authors.lastname: Astephen Wilson
authors.forename: K J
authors.initials: KJ
authors.lastname: Deluzio
authors.forename: M J
authors.initials: MJ
authors.lastname: Dunbar
authors.forename: G E
authors.initials: GE
authors.lastname: Caldwell
authors.forename: C L
authors.initials: CL
authors.lastname: Hubley-Kozey
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D004576:Electromyography; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D018482:Muscle, Skeletal / Q000503:physiopathology*; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000503:physiopathology*; D010147:Pain Measurement; D011859:Radiography; D012720:Severity of Illness Index; D016138:Walking / Q000502:physiology