title: Factors for pain in patients with different grades of knee osteoarthritis.
abstract: OBJECTIVE
  Discordance between having pain and radiologic osteoarthritis (OA) is a well-established fact. It is suggested that this particularly applies to the less severe grades of OA. However, some people with a Kellgren/Lawrence (K/L) grade of 3 or 4 for OA are without pain. This study aimed to identify factors and differences in the factors associated with pain in persons with different grades of knee OA.
  
  
  METHODS
  We stratified the knees of more than 5,000 participants of a population-based cohort study, the Rotterdam Study, based on the grade of knee OA. Multivariate generalized estimating equation analysis was used to analyze the association with knee pain. We tested several factors not directly related to structural damage of the knee.
  
  
  RESULTS
  As expected, an increasing percentage of participants did not report pain with decreasing severity of knee OA: 25.8% for K/L grade 3 or 4 and 84.5% for no knee OA. Being a woman, having widespread pain, reporting general health symptoms, familial OA, and morning stiffness are factors for knee pain, but not specific for a particular grade of radiographic knee OA. Depression and hip OA showed significant interactions with the grade of OA being a factor for knee pain in knees without OA (K/L grade 0), but not in knees with OA. In addition, increasing age is protective for reporting pain in general.
  
  
  CONCLUSIONS
  Several factors are associated with knee pain, but are not specific for a grade of radiographic knee OA. Two factors were associated with knee pain in the knee without signs of OA.
authors.affiliation: Department of General Practice, Erasmus MC, Rotterdam, The Netherlands. d.schiphof@erasmusmc.nl
authors.forename: Dieuwke
authors.initials: D
authors.lastname: Schiphof
authors.forename: Hanneke J M
authors.initials: HJ
authors.lastname: Kerkhof
authors.forename: Jurgen
authors.initials: J
authors.lastname: Damen
authors.forename: Bianca M
authors.initials: BM
authors.lastname: de Klerk
authors.forename: Albert
authors.initials: A
authors.lastname: Hofman
authors.forename: Bart W
authors.initials: BW
authors.lastname: Koes
authors.forename: Joyce B J
authors.initials: JB
authors.lastname: van Meurs
authors.forename: Sita M A
authors.initials: SM
authors.lastname: Bierma-Zeinstra
mesh_terms: D000368:Aged; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000175:diagnosis* / Q000453:epidemiology*; D010146:Pain / Q000175:diagnosis* / Q000453:epidemiology*; D010147:Pain Measurement / Q000379:methods*; D011159:Population Surveillance / Q000379:methods; D011446:Prospective Studies