title: Patellofemoral joint stress during stair ascent and descent in persons with and without patellofemoral pain.
abstract: OBJECTIVE
  To determine if persons with patellofemoral pain (PFP) demonstrate elevated patellofemoral joint (PFJ) stress during stair ascent and descent when compared to persons without PFP.
  
  
  METHODS
  A cross sectional study utilizing an experimental and a control group.
  
  
  BACKGROUND
  Ascending and descending stairs is one of the most painful activities of daily living for persons with PFP. Whether or not the pain associated with stair ambulation is the result of elevated joint stress (force per unit area) has not been explored.
  
  
  METHODS
  10 subjects with a diagnosis of PFP and 10 subjects without pain completed two phases of data collection, (1) MRI assessment to determine PFJ contact area and (2) comprehensive motion analysis during stair ambulation at self selected climbing velocities. Data obtained from both data collection sessions were utilized as input variables into a biomechanical model to quantify PFJ stress.
  
  
  RESULTS
  Although the knee extensor moment and PFJ reaction force (PFJRF) were significantly reduced in the PFP subjects during stair ascent, there was no difference in PFJ stress between groups. Similarly, there were no differences in PFJ stress during stair descent.
  
  
  CONCLUSIONS
  Our results do not support the hypothesis that subjects with PFP demonstrate greater joint stress during stair ascent and descent compared to subjects without pain. However, subjects with PFP appeared to maintain normal levels of PFJ stress by minimizing the PFJRF. This was accomplished through a slower cadence and a reduced knee extensor moment.
  
  
  CONCLUSIONS
  PFP is a common syndrome causing pain and functional limitations during stair climbing and other activities requiring high levels of quadriceps activity. Information obtained from this study will be useful in understanding the biomechanical mechanisms contributing to functional deficits in the PFP population.
authors.affiliation: Department of Physical Therapy, Chapman University, One University Drive, Orange, CA 92866, USA. brechter@chapman.edu
authors.forename: Jacklyn Heino
authors.initials: JH
authors.lastname: Brechter
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Powers
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D003430:Cross-Sectional Studies; D005260:Female; D005269:Femur / Q000502:physiology* / Q000503:physiopathology; D006801:Humans; D007719:Knee Joint / Q000502:physiology* / Q000503:physiopathology; D008124:Locomotion / Q000502:physiology*; D008279:Magnetic Resonance Imaging; D008297:Male; D010146:Pain / Q000503:physiopathology; D010329:Patella / Q000502:physiology* / Q000503:physiopathology