title: Relationship between the Western Ontario and McMaster Universities Osteoarthritis Index Physical Function Subscale and physical performance measures in patients with hip osteoarthritis.
abstract: OBJECTIVE
  To examine the convergent and factor validity of the Western Ontario and McMaster Universities Osteoarthritis Index physical function subscale (WOMAC-PF) using a battery of physical performance measures (PPMs) in patients with non-end-stage hip osteoarthritis (OA).
  
  
  METHODS
  Cross-sectional data.
  
  
  METHODS
  A university physiotherapy research center.
  
  
  METHODS
  Patients with a clinical diagnosis of hip OA (N=93) referred for participation in research.
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  Factor validity of the WOMAC-PF was evaluated by using confirmatory factor analysis (CFA). Exploratory factor analysis (EFA) was run to determine whether WOMAC-PF and PPMs were capturing separate aspects of physical function. Covariates including pain, depression, Pain Beliefs Screening Instrument, body mass index, hip flexion, use of an assistive device, and lower-extremity strength were included in the EFA as independent variables.
  
  
  RESULTS
  CFA of the WOMAC-PF yielded a 1-factor solution accounting for 84% of the variance in the data (eigenvalue=11). EFA yielded a 2-factor solution accounting for 68% of the variance in the data. The PPMs and the WOMAC-PF loaded on separate factors.
  
  
  CONCLUSIONS
  We were unable to confirm a 4-factor solution model of the WOMAC-PF as previously reported. This suggests that the WOMAC-PF shows sufficient factor validity in capturing perceived physical function in patients with non-end-stage hip OA but captures a different construct than that of PPMs, confirming the need for both when evaluating functional outcome. Furthermore, we suggest a new standardized battery of physical performance measures to serve as the criterion standard against which self-report measures could be compared.
authors.affiliation: Centre for Physiotherapy Research, University of Otago, Dunedin, New Zealand. lexie.wright@gmail.com
authors.forename: Alexis A
authors.initials: AA
authors.lastname: Wright
authors.forename: Chad E
authors.initials: CE
authors.lastname: Cook
authors.forename: G David
authors.initials: GD
authors.lastname: Baxter
authors.forename: Jose
authors.initials: J
authors.lastname: Garcia
authors.forename: J Haxby
authors.initials: JH
authors.lastname: Abbott
mesh_terms: D000203:Activities of Daily Living; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D003863:Depression / Q000209:etiology; D004185:Disability Evaluation; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000150:complications / Q000534:rehabilitation*; D010146:Pain / Q000209:etiology; D026741:Physical Therapy Modalities; D016059:Range of Motion, Articular; D015203:Reproducibility of Results; D012656:Self-Help Devices / Q000706:statistics & numerical data