title: Knee flexion during stair ambulation is altered in individuals with patellofemoral pain.
abstract: Reduced knee flexion is a logical gait adaptation for individuals with patellofemoral pain (PFP) to lessen the patellofemoral joint reaction force and minimise pain during stair ambulation. This gait adaptation may be related to the co-ordination of individual vasti components.
  
  
  OBJECTIVE
  This study investigated the amount of stance-phase knee flexion in individuals with (n=48) and without (n=18) PFP using a cross-sectional design. The relationship between stance-phase knee flexion and onset timing of individual vasti activity was also examined.
  
  
  METHODS
  Stance-phase knee flexion was measured in 2-dimensions using a PEAK movement analysis system during stair ascent and descent. Individuals with PFP were separated into those with synchronous onset of the EMG activity of vastus medialis obliquus (VMO) and vastus lateralis (VL), and those where the onset of VMO EMG activity was delayed relative to the VL.
  
  
  RESULTS
  The amount of knee flexion at heel-strike and peak was less in the individuals with PFP compared with the healthy controls. In addition, there were trends towards individuals with PFP who had a delayed EMG onset of VL having reduced knee flexion during stair descent compared with PFP individuals with simultaneous vasti onsets and the control participants.
  
  
  CONCLUSIONS
  These results indicate that the amount of stance-phase knee flexion is lower in individuals with PFP and that this may be related to onset timing of the vasti.
authors.affiliation: Centre for Sports Medicine Research and Education, School of Physiotherapy, The University of Melbourne, Victoria 3010, Australia. k.crossley@unimelb.edu.au
authors.forename: Kay M
authors.initials: KM
authors.lastname: Crossley
authors.forename: Sallie M
authors.initials: SM
authors.lastname: Cowan
authors.forename: Kim L
authors.initials: KL
authors.lastname: Bennell
authors.forename: Jenny
authors.initials: J
authors.lastname: McConnell
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D003430:Cross-Sectional Studies; D004576:Electromyography; D005260:Female; D005269:Femur / Q000503:physiopathology*; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D009068:Movement; D010146:Pain / Q000503:physiopathology*; D010329:Patella / Q000503:physiopathology*; D016059:Range of Motion, Articular / Q000502:physiology*; D016138:Walking / Q000502:physiology*