title: Toward a clinical definition of early osteoarthritis: onset of patient-reported knee pain begins on stairs. Data from the osteoarthritis initiative.
abstract: OBJECTIVE
  Early detection of osteoarthritis (OA) would increase the chances of effective intervention. We aimed to investigate which patient-reported activity is first associated with knee pain. We hypothesized that pain would occur first during activities requiring weight bearing and knee bending.
  
  
  METHODS
  Data were obtained from the Osteoarthritis Initiative (OAI), a multicenter, longitudinal prospective observational cohort of people who have or are at high risk of OA. Participants completed the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC; Likert scale) annually for up to 7 years. Rasch analysis was used to rank the WOMAC pain questions (activities) in order of affirmation as the pain score increased from 0. For each total WOMAC score category (0-20) we selected 25 individuals at random based on their maximum score across all visits. Fit to the Rasch model was assessed in this subset; stability of question ranking over successive visits was confirmed in the full OAI.
  
  
  RESULTS
  WOMAC data on 4,673 people were included, with 491 selected for subset analysis. The subset data showed good fit to the Rasch model (χ(2) = 43.31, P = 0.332). In the full OAI, the "using stairs" question was the first to score points as the total pain score increased from 0 (baseline logit score ± 95% confidence interval -4.74 ± 0.07), then "walking" (-2.94 ± 0.07), "standing" (-2.65 ± 0.07), "lying/sitting" (-2.00 ± 0.08), and finally "in bed" (-1.32 ± 0.09). This ordering was consistent over successive visits.
  
  
  CONCLUSIONS
  Knee pain is most likely to first appear during weight-bearing activities involving bending of the knee, such as using stairs. First appearance of this symptom may identify a group suitable for early intervention strategies.
authors: Leeds Institute of Rheumatic and Musculoskeletal Medicine, University of Leeds, and NIHR Leeds Musculoskeletal Biomedical Research Unit, Leeds, UK.
authors: Elizabeth M A
authors: EM
authors: Hensor
authors: Bright
authors: B
authors: Dube
authors: Sarah R
authors: SR
authors: Kingsbury
authors: Alan
authors: A
authors: Tennant
authors: Philip G
authors: PG
authors: Conaghan
mesh_terms: D000203:Activities of Daily Living / Q000523:psychology; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D042241:Early Diagnosis; D005260:Female; D005684:Gait / Q000502:physiology; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000175:diagnosis* / Q000453:epidemiology / Q000523:psychology; D010147:Pain Measurement / Q000379:methods / Q000592:standards*; D011446:Prospective Studies; D057566:Self Report / Q000592:standards*