title: Altered vastii recruitment when people with patellofemoral pain syndrome complete a postural task.
abstract: OBJECTIVE
  To investigate the recruitment of the vastus medialis obliquus (VMO) and vastus lateralis during voluntary tasks that challenge the stability of the knee and to evaluate whether there is a change in the coordination of the postural response by the central nervous system in subjects with patellofemoral pain syndrome (PFPS).
  
  
  METHODS
  Cross-sectional.
  
  
  METHODS
  University laboratory in Australia.
  
  
  METHODS
  Thirty-seven subjects with PFPS and 37 asymptomatic sex-matched controls.
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  Recordings of electromyographic activity of the VMO, vastus lateralis, tibialis anterior, and soleus were made by using surface electrodes. Subjects rose onto their toes (rise task) or rocked back on their heels (rock task) in a visual choice-reaction time task. Electromyographic onsets were determined by using a computer algorithm and were verified visually.
  
  
  RESULTS
  Our results confirm that, in asymptomatic subjects, contraction of the VMO and vastus lateralis occurs as part of the feed-forward postural response associated with ankle movements in standing, and the contraction of these separate heads of the quadriceps group occurs simultaneously. However, when subjects with PFPS perform identical tasks, the electromyographic onset of the vastus lateralis occurs before that of the VMO.
  
  
  CONCLUSIONS
  These findings indicate a difference in motor control in subjects with PFPS. They also support the hypothesized relation between changes in the timing of activity of the vastii and PFPS and provide the theoretic rationale to support physiotherapy treatment commonly used in the management of PFPS.
authors.affiliation: Centre for Sports Medicine Research and Education, School of Physiotherapy, University of Melbourne, Australia. s.cowan@unimelb.edu.au
authors.forename: Sallie M
authors.initials: SM
authors.lastname: Cowan
authors.forename: Paul W
authors.initials: PW
authors.lastname: Hodges
authors.forename: Kim L
authors.initials: KL
authors.lastname: Bennell
authors.forename: Kay M
authors.initials: KM
authors.lastname: Crossley
mesh_terms: D000328:Adult; D003430:Cross-Sectional Studies; D004576:Electromyography; D005260:Female; D005267:Femoral Nerve / Q000503:physiopathology*; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology / Q000503:physiopathology*; D010146:Pain / Q000503:physiopathology*; D010329:Patella / Q000503:physiopathology*; D011187:Posture; D011930:Reaction Time / Q000502:physiology; D011999:Recruitment, Neurophysiological; D012016:Reference Values; D013577:Syndrome