title: Physical activity and incident clinical knee osteoarthritis in older adults.
abstract: OBJECTIVE
  To study the relationship between 4 components of physical activity and the 12-year incidence of clinical knee osteoarthritis (OA) among older adults.
  
  
  METHODS
  Longitudinal data from 1,678 men and women, ages 55-85 years, were collected in the Longitudinal Aging Study Amsterdam. Incident clinical knee OA was defined by an algorithm using self-report and general practitioner data. Physical activity was assessed by a validated questionnaire from which 4 physical activity component scores were created: muscle strength, intensity, mechanical strain, and turning actions. Cox proportional hazards models were conducted to examine the relationship between these scores and incident knee OA and reported as hazard ratios (HRs) with 95% confidence intervals (95% CIs).
  
  
  RESULTS
  During 12 years of followup, 463 respondents (28%) developed clinical knee OA. A high mechanical strain score (HR 1.43, 95% CI 1.15-1.77) and a low muscle strength score (HR 1.30, 95% CI 1.01-1.68) were associated with an increased risk of knee OA after adjustment for age, sex, region of living, education, lifetime physical work demands, lifetime general physical activity, body mass index, current total physical activity level, and depression. No association was observed in the intensity and turning actions components. The results were similar for men and women, and for obese and nonobese respondents.
  
  
  CONCLUSIONS
  Older adults who perform low muscle strength activities or activities causing high mechanical strain had an increased risk of clinical knee OA. These results suggest that specific components of physical activity may influence the development of knee OA.
authors.affiliation: Institute for Research in Extramural Medicine, VU University Medical Center, Amsterdam, The Netherlands. l.verweij@vumc.nl
authors.forename: Lisanne M
authors.initials: LM
authors.lastname: Verweij
authors.forename: Natasja M
authors.initials: NM
authors.lastname: van Schoor
authors.forename: Dorly J H
authors.initials: DJ
authors.lastname: Deeg
authors.forename: Joost
authors.initials: J
authors.lastname: Dekker
authors.forename: Marjolein
authors.initials: M
authors.lastname: Visser
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D012090:Cumulative Trauma Disorders / Q000150:complications; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D018908:Muscle Weakness / Q000150:complications*; D020370:Osteoarthritis, Knee / Q000209:etiology*; D016016:Proportional Hazards Models