title: Longitudinal impact of joint pain comorbidity on quality of life and activity levels in knee osteoarthritis: data from the Osteoarthritis Initiative.
abstract: OBJECTIVE
  Joint pain comorbidity (JPC) is common in individuals with knee OA. This study investigates the longitudinal association between JPC and health-related quality of life (HRQoL) and physical activity levels in individuals with knee OA.
  
  
  METHODS
  Data from the progression cohort of the Osteoarthritis Initiative (n = 1233; age 61 years and 58% females) were analysed. JPC was considered present if individuals reported pain in three or more joint groups, including the knee joints. HRQoL was assessed using the Knee Injury and Osteoarthritis Outcome Score (KOOS) Quality of Life subscale, and self-reported physical activity was determined using the Physical Activity Scale for the Elderly (PASE). Generalized estimating equation (GEE) analyses were performed, adjusted for age, sex, duration of complaints, medical comorbidity, and physical and mental functioning.
  
  
  RESULTS
  Over the 4-year period, 32% of participants never reported JPC, whereas 12% always reported JPC. GEE modelling demonstrated that having JPC was negatively associated with HRQoL [regression coefficient β (95% CI) -3.57 (-4.69, -2.44)] and not associated with physical activity [-1.32 (-6.61, 3.98)].
  
  
  CONCLUSIONS
  Considering the impact of JPC on the HRQoL of individuals with knee OA, the assessment of JPC in individuals with knee OA might be a daily routine.
authors.affiliation: Department of Rheumatology, Sint Maartenskliniek, Nijmegen, The Netherlands.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Hoogeboom
authors.forename: Alfons A
authors.initials: AA
authors.lastname: den Broeder
authors.forename: Rob A
authors.initials: RA
authors.lastname: de Bie
authors.forename: Cornelia H M
authors.initials: CH
authors.lastname: van den Ende
mesh_terms: D000368:Aged; D018771:Arthralgia / Q000453:epidemiology* / Q000523:psychology; D015331:Cohort Studies; D015897:Comorbidity; D017281:Cost of Illness; D018450:Disease Progression; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D020370:Osteoarthritis, Knee / Q000453:epidemiology* / Q000523:psychology; D011446:Prospective Studies; D011788:Quality of Life; D011795:Surveys and Questionnaires