title: Effect of recreational physical activities on the development of knee osteoarthritis in older adults of different weights: the Framingham Study.
abstract: OBJECTIVE
  To evaluate the long-term effect of recreational exercise on the development of knee osteoarthritis (OA) in a community-based cohort of older adults, many of whom were overweight or obese.
  
  
  METHODS
  Subjects were asked about recreational activities including walking or jogging for exercise and working up a sweat, and were asked to compare their activity levels with others. Subjects were then asked about knee pain and weight-bearing anteroposterior and lateral knee radiographs were obtained. Approximately 9 years later, subjects were reexamined for OA. Radiographs were read for OA features in both tibiofemoral and patellofemoral compartments and were scored for tibiofemoral joint space narrowing. To evaluate incident OA, we excluded knees with OA at baseline for all analyses and focused on 3 knee-specific outcomes: incident radiographic OA, symptomatic OA, and tibiofemoral joint space loss. After adjusting for age, sex, body mass index (BMI), knee injury history, and correlation between knees, we evaluated the association of each recreational activity with OA development.
  
  
  RESULTS
  A total of 1,279 subjects underwent both baseline and followup examinations (mean age at baseline 53.2 years). Neither recreational walking, jogging, frequent working up a sweat, nor high activity levels relative to peers were associated with a decrease or increase in risk of OA. Joint space loss was also unaffected by activity. Persons with BMI above the median (27.7 kg/m(2) for men and 25.7 kg/m(2) for women; mean BMI >30 kg/m(2) for both) had no increases in risk of OA by different type of activity.
  
  
  CONCLUSIONS
  Among middle-aged and elderly persons without knee OA, many of whom were overweight, recreational exercise neither protects against nor increases risk of knee OA.
authors.affiliation: Clinical Epidemiology Unit, Boston University School of Medicine, Boston, Massachusetts, USA. dfelson@bu.edu
authors.forename: David T
authors.initials: DT
authors.lastname: Felson
authors.forename: Jingbo
authors.initials: J
authors.lastname: Niu
authors.forename: Margaret
authors.initials: M
authors.lastname: Clancy
authors.forename: Burton
authors.initials: B
authors.lastname: Sack
authors.forename: Piran
authors.initials: P
authors.lastname: Aliabadi
authors.forename: Yuqing
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D018771:Arthralgia / Q000209:etiology / Q000503:physiopathology; D015992:Body Mass Index; D015331:Cohort Studies; D015444:Exercise; D005260:Female; D006801:Humans; D015994:Incidence; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000503:physiopathology; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000150:complications / Q000000981:diagnostic imaging / Q000209:etiology* / Q000517:prevention & control*; D011859:Radiography; D011998:Recreation / Q000502:physiology*; D012307:Risk Factors; D016474:Weight-Bearing / Q000502:physiology