title: Incident knee pain in the Nottingham community: a 12-year retrospective cohort study.
abstract: OBJECTIVE
  To determine the community incidence of knee pain and associated risk factors over a 12-year period in people over the age of 40 years.
  
  
  METHODS
  A cohort study of knee pain was undertaken in 2156 people from four general practices in North Nottinghamshire, UK. Knee pain was defined as 'pain around the knee for most days of at least a month'. Cumulative incidence over 12 years and person-year incidence rate of knee pain were estimated. Survival analysis was undertaken for time to the onset of knee pain. Hazard ratio (HR) and 95% confidence interval (CI) were estimated for relative risk between exposure and non-exposure. Cox regression model was used to adjust for confounding factors.
  
  
  RESULTS
  The 12-year cumulative incidence of knee pain was 34.4% (32% for men and 35% for women), corresponding to an average incidence rate of 32 (31 for men and 34 for women)/1000 person-years. Incident knee pain was associated with female gender (HR 1.27, 95% CI 1.08, 1.49), obesity (1.80; 95% CI 1.37, 2.38), varus (1.68, 95% CI 1.15, 2.47) and valgus (1.83, 95% CI 1.05, 3.20) mal-alignment, and knee injury (2.37, 95% CI 2.98, 2.85).
  
  
  CONCLUSIONS
  For people over age 40, one in three will develop knee pain within 12 years. On average, the risk of knee pain was 32/1000 person-years. This risk is associated with a variety of constitutional and environmental biomechanical insults to the knee. Some of these could be modified to possibly reduce the incidence of the condition.
authors.affiliation: Academic Rheumatology, University of Nottingham, Clinical Sciences Building, City Hospital, Nottingham NG7 1PB, UK.
authors.forename: S L
authors.initials: SL
authors.lastname: Ingham
authors.forename: W
authors.initials: W
authors.lastname: Zhang
authors.forename: S A
authors.initials: SA
authors.lastname: Doherty
authors.forename: D F
authors.initials: DF
authors.lastname: McWilliams
authors.forename: K R
authors.initials: KR
authors.lastname: Muir
authors.forename: M
authors.initials: M
authors.lastname: Doherty
mesh_terms: D000328:Adult; D000368:Aged; D015331:Cohort Studies; D004739:England / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009140:Musculoskeletal Diseases / Q000150:complications*; D010146:Pain / Q000453:epidemiology*; D011859:Radiography; D012307:Risk Factors; D016019:Survival Analysis