title: The natural history of radiographic knee osteoarthritis: a fourteen-year population-based cohort study.
abstract: OBJECTIVE
  To establish the natural history of radiographic knee osteoarthritis (OA) over 14 years in a community-based cohort.
  
  
  METHODS
  We examined women from the Chingford Women's Study, a community-based cohort followed up for more than 14 years. We selected women for whom bilateral radiographs of the knees (with the legs in full extension) were obtained at approximately 5-year intervals. Radiographs were scored for OA in a blinded manner, using Kellgren/Lawrence (K/L) grades. Descriptive statistics and odds ratios (ORs) were used to compare the incidence, worsening, and progression of radiographic knee OA.
  
  
  RESULTS
  A complete radiography series was available for 561 of the original 1,003 subjects enrolled in the study. The median age of these subjects at baseline was 53 years (interquartile range 48-58 years). At baseline, 13.7% of the subjects had radiographic knee OA (K/L grade≥2) in at least one knee, and the prevalence increased to 47.8% by year 15. The annual cumulative incidence of radiographic knee OA was 2.3% between baseline and year 15. The annual rates of disease progression and worsening between baseline and year 15 were 2.8% and 3.0%, respectively. Subjects with a K/L grade of 1 at baseline were more likely to experience worsening by year 15 compared with subjects with a baseline grade of 0 (OR 4.5, 95% confidence interval 2.7-7.4).
  
  
  CONCLUSIONS
  This is the longest natural history study of radiographic knee OA to date. The results showed relatively low rates for the incidence and progression of radiographic knee OA; more than half of all subjects had no radiographic evidence of knee OA over a 15-year period of time. Subjects with a baseline K/L grade of 1 were more likely than subjects with other baseline K/L grades to experience worsening of knee OA.
authors.affiliation: Botnar Research Centre, Institute of Musculoskeletal Sciences, University of Oxford, Oxford, UK.
authors.forename: K M
authors.initials: KM
authors.lastname: Leyland
authors.forename: D J
authors.initials: DJ
authors.lastname: Hart
authors.forename: M K
authors.initials: MK
authors.lastname: Javaid
authors.forename: A
authors.initials: A
authors.lastname: Judge
authors.forename: A
authors.initials: A
authors.lastname: Kiran
authors.forename: A
authors.initials: A
authors.lastname: Soni
authors.forename: L M
authors.initials: LM
authors.lastname: Goulston
authors.forename: C
authors.initials: C
authors.lastname: Cooper
authors.forename: T D
authors.initials: TD
authors.lastname: Spector
authors.forename: N K
authors.initials: NK
authors.lastname: Arden
mesh_terms: D000328:Adult; D000368:Aged; D015331:Cohort Studies; D018450:Disease Progression; D005260:Female; D006801:Humans; D015994:Incidence; D007719:Knee Joint / Q000000981:diagnostic imaging*; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging* / Q000453:epidemiology; D015995:Prevalence; D011859:Radiography