title: Relationship between years in the trade and the development of radiographic knee osteoarthritis and MRI-detected meniscal tears and bursitis in floor layers. A cross-sectional study of a historical cohort.
abstract: OBJECTIVE
  An increased risk of developing knee disorders including radiographic knee osteoarthritis (OA) have been shown among workers with kneeling working demands. There may also be a dose-related association between duration of employment in occupations with kneeling work and development of radiographic knee OA and magnetic resonance imaging (MRI)-detected meniscal tears and bursitis.
  
  
  METHODS
  A cross-sectional study of a historical cohort.
  
  
  METHODS
  Members of the trade unions for floor layers and graphic designers in Denmark.
  
  
  METHODS
  92 male floor layers and 49 graphic designers aged 36-70 years were randomly selected among participants from a clinical and radiographic study of 156 floor layers and 152 graphic designers.
  
  
  METHODS
  Radiographic tibiofemoral (TF) and patellofemoral (PF) knee-OA and MRI-detected meniscal tears and bursitis. Results were adjusted for age, earlier knee traumas, sports activities and body mass index in logistic regression models. Association between TF OA and years in the floor-laying trade was graphically examined by a restricted cubic spline with four knots.
  
  
  RESULTS
  Increase in number of years with exposure to kneeling work is associated with radiographic TF knee OA with ORs 0.7, 95% CI 0.07 to 4.42; OR 1.89, 95% CI 0.29 to 12.3; OR 4.82, 95% CI 1.38 to 17 for <20 years, 20-30 years and >30 years of kneeling work, respectively. MRI-verified medial meniscal tears was increased among subjects with kneeling work with OR 1.96, 95% CI 0.79 to 4.88 to OR 4.73, 95% CI 1.16 to 19.4 but was not associated with duration of employment. Periarticular bursitis was increased in subjects with <20 years of kneeling working activity. Lateral meniscal tears and PF knee OA were not associated with duration of kneeling working activity or with kneeling work in general.
  
  
  CONCLUSIONS
  The findings suggest a dose-response relationship for radiographic TF knee OA in floor layers with a significant amount of kneeling work and an increase of MRI-verified medial meniscal tears among workers with kneeling work.
authors.affiliation: Department of Occupational and Environmental Medicine, Bispebjerg Hospital, Copenhagen, Denmark.
authors.forename: Lilli Kirkeskov
authors.initials: LK
authors.lastname: Jensen
authors.forename: Søren
authors.initials: S
authors.lastname: Rytter
authors.forename: Jacob Louis
authors.initials: JL
authors.lastname: Marott
authors.forename: Jens Peter
authors.initials: JP
authors.lastname: Bonde