title: Moving to maintain function in knee osteoarthritis: evidence from the osteoarthritis initiative.
abstract: OBJECTIVE
  To investigate the association between baseline physical activity and 1-year functional performance in adults with knee osteoarthritis (OA).
  
  
  METHODS
  Prospective cohort study of knee OA development and progression with 1-year follow-up.
  
  
  METHODS
  Community.
  
  
  METHODS
  Osteoarthritis Initiative public data on adults with knee OA (n=2274; age, 45-79y) who participated in functional performance assessments (timed 20-m walk and chair stand test) at baseline and 1-year follow-up.
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  A good 1-year performance outcome (separately defined for walk time and chair stand measures) was improvement from baseline quintile or maintenance in the best quintile.
  
  
  RESULTS
  Almost 2 in 5 persons with radiographic knee OA improved or maintained high performance at 1 year. Physical activity measured by the Physical Activity Scale for the Elderly (PASE) was significantly associated with good walk rate and chair stand outcomes (odds ratio per 40 units PASE [95% confidence interval]=1.13 [1.13, 1.17] and 1.10 [1.05, 1.15], respectively), as were participation in sports/recreational activities (1.45 [1.23, 1.71] and 1.29 [1.09, 1.51], respectively) and lifestyle activities (1.11 [1.06, 1.16] and 1.09 [1.04, 1.14], respectively). An independent protective relationship for these physical activity measures approached significance after adjusting for sociodemographic and health factors. Older adults reported the least baseline physical activity and least frequent good 1-year outcomes.
  
  
  CONCLUSIONS
  These findings support public health recommendations to be physically active in order to preserve function for persons with knee OA. Physical activity messages should specifically target older adults whose low activity levels may jeopardize their ability to maintain functional performance.
authors.affiliation: Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA. ddunlop@northwestern.edu
authors.forename: Dorothy D
authors.initials: DD
authors.lastname: Dunlop
authors.forename: Pamela
authors.initials: P
authors.lastname: Semanik
authors.forename: Jing
authors.initials: J
authors.lastname: Song
authors.forename: Leena
authors.initials: L
authors.lastname: Sharma
authors.forename: Michael
authors.initials: M
authors.lastname: Nevitt
authors.forename: Rebecca
authors.initials: R
authors.lastname: Jackson
authors.forename: Jerry
authors.initials: J
authors.lastname: Mysiw
authors.forename: Rowland W
authors.initials: RW
authors.lastname: Chang
mesh_terms: D000368:Aged; D015992:Body Mass Index; D015444:Exercise; D005260:Female; D015438:Health Behavior; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000503:physiopathology / Q000628:therapy*; D010146:Pain / Q000503:physiopathology; D011446:Prospective Studies; D012959:Socioeconomic Factors