title: Exploring the relationships between International Classification of Functioning, Disability and Health (ICF) constructs of Impairment, Activity Limitation and Participation Restriction in people with osteoarthritis prior to joint replacement.
abstract: BACKGROUND
  The International Classification of Functioning, Disability and Health (ICF) proposes three main constructs, impairment (I), activity limitation (A) and participation restriction (P). The ICF model allows for all paths between the constructs to be explored, with significant paths likely to vary for different conditions. The relationships between I, A and P have been explored in some conditions but not previously in people with osteoarthritis prior to joint replacement. The aim of this paper is to examine these relationships using separate measures of each construct and structural equation modelling.
  
  
  METHODS
  A geographical cohort of 413 patients with osteoarthritis about to undergo hip and knee joint replacement completed the Aberdeen measures of Impairment, Activity Limitation and Participation Restriction (Ab-IAP). Confirmatory factor analysis was used to test the three factor (I, A, P) measurement model. Structural equation modelling was used to explore the I, A and P pathways in the ICF model.
  
  
  RESULTS
  There was support from confirmatory factor analysis for the three factor I, A, P measurement model. The structural equation model had good fit [S-B Chi-square = 439.45, df = 149, CFI robust = 0.91, RMSEA robust = 0.07] and indicated significant pathways between I and A (standardised coefficient = 0.76 p < 0.0001) and between A and P (standardised coefficient = 0.75 p < 0.0001). However, the path between I and P was not significant (standardised coefficient = 0.01).
  
  
  CONCLUSIONS
  The significant pathways suggest that treatments and interventions aimed at reducing impairment, such as joint replacement, may only affect P indirectly, through A, however, longitudinal data would be needed to establish this.
authors.affiliation: Aberdeen Health Psychology Group, University of Aberdeen, Aberdeen, UK. beth.pollard@abdn.ac.uk
authors.forename: Beth
authors.initials: B
authors.lastname: Pollard
authors.forename: Marie
authors.initials: M
authors.lastname: Johnston
authors.forename: Paul
authors.initials: P
authors.lastname: Dieppe
mesh_terms: D000203:Activities of Daily Living; D000368:Aged; D019644:Arthroplasty, Replacement, Hip; D019645:Arthroplasty, Replacement, Knee; D016009:Chi-Square Distribution; D004185:Disability Evaluation; D005260:Female; D006621:Hip Joint / Q000503:physiopathology / Q000601:surgery; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology / Q000601:surgery; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D015207:Osteoarthritis, Hip / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery; D020370:Osteoarthritis, Knee / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery; D010147:Pain Measurement; D011237:Predictive Value of Tests; D057234:Preoperative Period; D012606:Scotland; D012720:Severity of Illness Index; D012919:Social Behavior; D058992:Social Participation; D011795:Surveys and Questionnaires