title: Meeting physical activity guidelines and the risk of incident knee osteoarthritis: a population-based prospective cohort study.
abstract: OBJECTIVE
  Knee osteoarthritis (OA) is a leading cause of disability and joint pain. Although other risk factors of knee OA have been identified, how physical activity affects incident knee OA remains unclear.
  
  
  METHODS
  Using data from the first (1999-2004) and second (2005-2010) followup periods of the Johnston County Osteoarthritis Project study, we tested the association between meeting physical activity guidelines and incident knee outcomes among 1,522 adults ages ≥45 years. The median followup time was 6.5 years (range 4.0-10.2 years). Physical activity at baseline (moderate-equivalent physical activity minutes/week) was calculated using the Minnesota Leisure Time Physical Activity questionnaire. Incident knee radiographic OA (ROA) was defined as the development of Kellgren/Lawrence grade ≥2 in a knee at followup. Incident knee symptomatic ROA (sROA) was defined as the development of ROA and symptoms in at least 1 knee at followup. Weibull regression modeling was used to estimate hazard ratios (HRs) and 95% confidence intervals (95% CIs) for interval-censored data.
  
  
  RESULTS
  In multivariable models, meeting the 2008 Department of Health and Human Services (HHS) physical activity guidelines (≥150 minutes/week) was not significantly associated with ROA (HR 1.20 [95% CI 0.92-1.56]) or sROA (HR 1.24 [95% CI 0.87-1.76]). Adults in the highest level (≥300 minutes/week) of physical activity had a higher risk of knee ROA and sROA compared with inactive (0 to <10 minutes/week) participants; however, these associations were not statistically significant (HR 1.62 [95% CI 0.97-2.68] and HR 1.42 [95% CI 0.76-2.65], respectively).
  
  
  CONCLUSIONS
  Meeting the HHS physical activity guidelines was not associated with incident knee ROA or sROA in a cohort of middle-aged and older adults.
authors: Centers for Disease Control and Prevention, Atlanta, Georgia.
authors: K E
authors: KE
authors: Barbour
authors: J M
authors: JM
authors: Hootman
authors: C G
authors: CG
authors: Helmick
authors: L B
authors: LB
authors: Murphy
authors: Kristina A
authors: KA
authors: Theis
authors: T A
authors: TA
authors: Schwartz
authors: W D
authors: WD
authors: Kalsbeek
authors: J B
authors: JB
authors: Renner
authors: J M
authors: JM
authors: Jordan
mesh_terms: D000203:Activities of Daily Living; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D019983:Guideline Adherence; D017408:Guidelines as Topic; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D009657:North Carolina; D020370:Osteoarthritis, Knee / Q000453:epidemiology* / Q000503:physiopathology; D011446:Prospective Studies; D012044:Regression Analysis; D012189:Retrospective Studies; D012307:Risk Factors; D011795:Surveys and Questionnaires; D014481:United States; D014483:United States Dept. of Health and Human Services
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