title: Self-reported knee and foot alignments in early adult life and risk of osteoarthritis.
abstract: OBJECTIVE
  To determine whether self-reported early adult life malalignment of knees or feet are risk factors for knee or hip osteoarthritis (OA).
  
  
  METHODS
  Participants in the Genetics of Osteoarthritis and Lifestyle case-control database were sent a questionnaire (n = 3,022) containing line-drawing instruments for self-reported knee and foot alignment at ages 20-29 years. Respondents were categorized as having straight, valgus, or varus knee, and straight, toe-in, or toe-out feet. Radiographic criteria were used to define current isolated knee or hip OA, combined knee and hip OA, or non-OA controls. Odds ratios (ORs), adjusted ORs, and 95% confidence intervals (95% CIs) were calculated and logistic regression was performed.
  
  
  RESULTS
  The response rate was 72%; 87.5% of responders (n = 1,901) completed the alignment questions. Increased risk of isolated knee OA occurred with early adult varus (adjusted OR 5.16, 95% CI 2.87-9.41) and valgus knees (adjusted OR 3.16, 95% CI 1.04-9.64). The positive association between knee OA and toe-in foot was explained by varus knee. There was an increased risk of combined knee/hip OA from varus (adjusted OR 4.52, 95% CI 2.39-8.53) and valgus knees (adjusted OR 3.07, 95% CI 0.99-9.54). Varus knee was associated with risk of medial tibiofemoral OA, whereas valgus knee was associated with risk of lateral tibiofemoral and lateral patellofemoral OA. Toe-out foot was associated with reduced medial patellofemoral OA. For knee OA, a multiplicative interaction analysis between occupational risks and varus/valgus yielded an OR(int) of 3.20 (95% CI 1.08-9.49).
  
  
  CONCLUSIONS
  Constitutional alignment of the leg in terms of varus or valgus knee or foot rotation may be a significant factor in determining development and distribution of knee but not hip OA.
authors.affiliation: Academic Rheumatology, Clinical Sciences Building, University of Nottingham, City Hospital, Nottingham, UK. dan.mcwilliams@nottingham.ac.uk
authors.forename: Daniel F
authors.initials: DF
authors.lastname: McWilliams
authors.forename: Sally
authors.initials: S
authors.lastname: Doherty
authors.forename: Rose A
authors.initials: RA
authors.lastname: Maciewicz
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: Muir
authors.forename: Weiya
authors.initials: W
authors.lastname: Zhang
authors.forename: Michael
authors.initials: M
authors.lastname: Doherty
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D005260:Female; D005530:Foot Deformities / Q000150:complications*; D006801:Humans; D007593:Joint Instability; D007719:Knee Joint / Q000002:abnormalities*; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D015207:Osteoarthritis, Hip / Q000209:etiology; D020370:Osteoarthritis, Knee / Q000209:etiology*; D012307:Risk Factors