title: Occupation-related squatting, kneeling, and heavy lifting and the knee joint: a magnetic resonance imaging-based study in men.
abstract: OBJECTIVE
  We examined the relation between occupational exposures to frequent squatting/kneeling and/or heavy lifting with cartilage morphology, based on magnetic resonance imaging (MRI), at the tibiofemoral and patellofemoral joints in men and determined which compartments are most affected.
  
  
  METHODS
  We evaluated 192 men with symptomatic knee osteoarthritis (OA). The more symptomatic knee was imaged using MRI. Cartilage was scored using the Whole Organ MRI Score semiquantitative method at the medial and lateral tibiofemoral joint and patellofemoral joint. Occupational exposures to frequent squatting, kneeling, and/or heavy lifting were assessed using a validated questionnaire.
  
  
  RESULTS
  Among the 192 men [mean (+/- standard deviation) age 69 +/- 9 yrs, body mass index (BMI) 30.8 +/- 4.7 kg/m(2)], those reporting occupational exposure to squatting/kneeling alone, heavy lifting alone, both squatting/kneeling and heavy lifting, or none of these activities numbered 7, 40, 47, and 98, respectively. Compared with men with no occupational exposure to these activities, and following adjustment for age, BMI, and history of knee injury or surgery, we found that men reporting occupational exposures to both squatting/kneeling and heavy lifting had a modest increased risk for worse cartilage morphology scores at the patellofemoral joint [odds ratio (OR) 1.8, 95% confidence interval (CI) 1.1 to 3.2] and medial tibiofemoral joint (OR 1.6, 95% CI 0.9, 3.0), although the latter did not reach statistical significance.
  
  
  CONCLUSIONS
  Men with frequent occupational squatting/kneeling and heavy lifting have a greater likelihood for worse cartilage morphology scores at the patellofemoral joint. These findings add support to the important role of biomechanical loading on the pathogenesis of knee OA, particularly patellofemoral OA.
authors.affiliation: College of Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA. amin.shreyasee@mayo.edu
authors.forename: Shreyasee
authors.initials: S
authors.lastname: Amin
authors.forename: Joyce
authors.initials: J
authors.lastname: Goggins
authors.forename: Jingbo
authors.initials: J
authors.lastname: Niu
authors.forename: Ali
authors.initials: A
authors.lastname: Guermazi
authors.forename: Mikayel
authors.initials: M
authors.lastname: Grigoryan
authors.forename: David J
authors.initials: DJ
authors.lastname: Hunter
authors.forename: Harry K
authors.initials: HK
authors.lastname: Genant
authors.forename: David T
authors.initials: DT
authors.lastname: Felson
mesh_terms: D000368:Aged; D015331:Cohort Studies; D006801:Humans; D007719:Knee Joint / Q000473:pathology*; D017770:Lifting / Q000009:adverse effects*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009784:Occupational Diseases / Q000473:pathology*; D016017:Odds Ratio; D020370:Osteoarthritis, Knee / Q000473:pathology*