title: Delayed onset of quadriceps activity and altered knee joint kinematics during stair stepping in individuals with knee osteoarthritis.
abstract: OBJECTIVE
  To determine if the electromyographic onset of vastus lateralis and kinematic knee joint motion in individuals with knee osteoarthritis (OA) differs from that of asymptomatic persons, during the task of stair stepping.
  
  
  METHODS
  Cross-sectional.
  
  
  METHODS
  University laboratory in Australia.
  
  
  METHODS
  Twenty-five participants with symptomatic knee OA and 33 asymptomatic controls.
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  Surface electromyography to determine the onset of vastus lateralis activity. Two-dimensional kinematic analysis of sagittal plane knee motion during stance phase of stair ascent and descent.
  
  
  RESULTS
  Participants with knee OA showed delayed onset of vastus lateralis activity during stair descent (P<.05) but not ascent. Both groups displayed a similar total range of knee motion. However, during stair descent, participants with OA had less knee flexion during early stance (P<.05) than controls.
  
  
  CONCLUSIONS
  Individuals with knee OA display altered quadriceps function and knee joint kinematics during stair descent. These impairments may have implications for force attenuation across the knee joint and warrant future investigation.
authors.affiliation: Centre for Sports Medicine Research and Education, School of Physiotherapy, University of Melbourne, Australia. r.hinman@pgrad.unimelb.edu.au
authors.forename: Rana S
authors.initials: RS
authors.lastname: Hinman
authors.forename: Kim L
authors.initials: KL
authors.lastname: Bennell
authors.forename: Ben R
authors.initials: BR
authors.lastname: Metcalf
authors.forename: Kay M
authors.initials: KM
authors.lastname: Crossley
mesh_terms: D001696:Biomechanical Phenomena; D003430:Cross-Sectional Studies; D004576:Electromyography; D015444:Exercise / Q000502:physiology; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology*; D018482:Muscle, Skeletal / Q000503:physiopathology*; D020370:Osteoarthritis, Knee / Q000534:rehabilitation*