title: Physical workload and the risk of severe knee osteoarthritis.
abstract: OBJECTIVE
  This study investigated the impact of physical workload on the risk of severe knee osteoarthritis (OA) leading to knee arthroplasty.
  
  
  METHODS
  In this case-referent study, the cases were 55- to 75-year-old men (N=55) and women (N=226) who had undergone their first knee arthroplasty operation for primary knee OA in the Kuopio University Hospital in 1992-1993. The referents (N=524) were from the same source population and were matched with the cases for age and gender. Information on explanatory variables was obtained by a computer-assisted telephone interview. Exposure was assessed up to 49 years of age.
  
  
  RESULTS
  After adjustment for body mass index, knee injury and leisure-time physical activity, an increased relative risk of knee OA was found for a history of high physical workload. The odds ratio (OR) was 1.53 [95% confidence interval (95% CI) 0.42-5.56] for the men and 2.03 (95% CI 1.03-3.99) for the women as compared with those with low physical workload. With respect to generic risk factors, climbing already at a medium level of exposure was associated with an increased risk of knee OA among the men (OR 3.06, 95% CI 1.25-7.46) and kneeling and squatting was a risk factor for both genders. Of the different trades, agriculture, forestry, fishing, transportation, and traffic showed the highest risks of knee OA.
  
  
  CONCLUSIONS
  The results of this study agree with the hypotheses that heavy physical loading increases the risk of knee OA and that cumulative physical stress has a deleterious effect on the knee joint.
authors.affiliation: Department of Public Health and General Practice, University of Kuopio, Kuopio Regional Institute of Occupational Health, Finland. pirjo.manninen@ttl.fi
authors.forename: Pirjo
authors.initials: P
authors.lastname: Manninen
authors.forename: Markku
authors.initials: M
authors.lastname: Heliövaara
authors.forename: Hilkka
authors.initials: H
authors.lastname: Riihimäki
authors.forename: Olavi
authors.initials: O
authors.lastname: Suoma-Iainen
mesh_terms: D017677:Age Distribution; D000368:Aged; D019645:Arthroplasty, Replacement, Knee; D016022:Case-Control Studies; D015331:Cohort Studies; D016001:Confidence Intervals; D005260:Female; D005387:Finland / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009784:Occupational Diseases / Q000453:epidemiology / Q000209:etiology*; D016017:Odds Ratio; D020370:Osteoarthritis, Knee / Q000453:epidemiology* / Q000209:etiology* / Q000601:surgery; D005082:Physical Exertion; D018570:Risk Assessment; D012720:Severity of Illness Index; D017678:Sex Distribution; D013314:Stress, Mechanical; D016526:Workload