title: Frequency of varus and valgus thrust and factors associated with thrust presence in persons with or at higher risk of developing knee osteoarthritis.
abstract: OBJECTIVE
  Varus thrust observed during gait has been shown to be associated with a 4-fold increase in the risk of medial knee osteoarthritis (OA) progression. Valgus thrust is believed to be less common than varus thrust; the prevalence of each is uncertain. Racial differences in risk factors may help explain variations in the natural history of knee OA. We undertook this study to determine the frequency of varus and valgus thrust in African Americans and Caucasians and to identify factors associated with thrust presence.
  
  
  METHODS
  The Osteoarthritis Initiative cohort includes men and women who have knee OA or are at increased risk of developing it. Trained examiners assessed thrust presence by gait observation. Logistic regression with generalized estimating equations was used to identify factors associated with thrust presence, and odds ratios (ORs) with 95% confidence intervals (95% CIs) were calculated.
  
  
  RESULTS
  Compared with Caucasians, African Americans had lower odds of varus thrust, controlling for age, sex, body mass index (BMI), injury, surgery, disease severity, strength, pain, and alignment in persons without knee OA (adjusted OR 0.50 [95% CI 0.36, 0.72]) and in those with knee OA (adjusted OR 0.46 [95% CI 0.34, 0.61]). Also independently associated with varus thrust were age, sex, BMI, disease severity, strength, and alignment. The odds of valgus thrust were greater for African Americans than for Caucasians in persons without knee OA (adjusted OR 1.69 [95% CI 1.02, 2.80]) and in those with knee OA (adjusted OR 1.98 [95% CI 1.35, 2.91]). Also independently associated with valgus thrust were disease severity and malalignment.
  
  
  CONCLUSIONS
  Compared with Caucasians, African Americans had lower odds of varus thrust and greater odds of valgus thrust. These findings may help explain the difference between these groups in the pattern of OA involvement at the knee.
authors.affiliation: Northwestern University, Chicago, Illinois 60611, USA.
authors.forename: Alison
authors.initials: A
authors.lastname: Chang
authors.forename: Marc
authors.initials: M
authors.lastname: Hochberg
authors.forename: Jing
authors.initials: J
authors.lastname: Song
authors.forename: Dorothy
authors.initials: D
authors.lastname: Dunlop
authors.forename: Joan S
authors.initials: JS
authors.lastname: Chmiel
authors.forename: Michael
authors.initials: M
authors.lastname: Nevitt
authors.forename: Karen
authors.initials: K
authors.lastname: Hayes
authors.forename: Charles
authors.initials: C
authors.lastname: Eaton
authors.forename: Joan
authors.initials: J
authors.lastname: Bathon
authors.forename: Rebecca
authors.initials: R
authors.lastname: Jackson
authors.forename: C Kent
authors.initials: CK
authors.lastname: Kwoh
authors.forename: Leena
authors.initials: L
authors.lastname: Sharma
mesh_terms: D001741:Black or African American / Q000706:statistics & numerical data*; D000368:Aged; D017760:Bone Malalignment / Q000000981:diagnostic imaging / Q000208:ethnology*; D005260:Female; D006801:Humans; D015994:Incidence; D007719:Knee Joint / Q000000981:diagnostic imaging; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000208:ethnology*; D011859:Radiography; D012307:Risk Factors; D012720:Severity of Illness Index; D044465:White People / Q000706:statistics & numerical data*