title: The relationship between toe-out angle during gait and progression of medial tibiofemoral osteoarthritis.
abstract: BACKGROUND
  A greater knee adduction moment increases risk of medial tibiofemoral osteoarthritis (OA) progression. Greater toe-out during gait shifts the ground reaction force vector closer to the centre of the knee, reducing the adduction moment. The present study was designed to test whether greater toe-out is associated with lower likelihood of medial OA progression.
  
  
  METHODS
  Baseline assessments included: kinematic/kinetic gait parameters using an optoelectronic camera system, force platform and inverse dynamics to calculate three-dimensional external knee moments; toe-out angle (formed by the line connecting heel strike and toe-off plantar surface centres of pressure and the forward progression line; knee pain; and full-limb alignment. Knee x-rays (semi-flexed) were obtained at baseline and at 18 months, with progression noted as medial joint space grade worsening. With logistic regression, odds ratios (ORs) for progression/5 degrees toe-out were estimated.
  
  
  RESULTS
  In the 56 subjects (59% women, mean age 66.6 years, body mass index (BMI) 29), baseline toe-out angle was less in knees with than without progression (difference -4.4, 95% CI -8.5 to -0.3). Greater toe-out was associated with reduced likelihood of progression (OR 0.60, 95% CI 0.37 to 0.98). Adjusting for age, gender, BMI, pain severity and disease severity, the OR was 0.62, 95% CI 0.36 to 1.06. Adjusting for adduction moment (second peak), the OR was 0.72, 95% CI 0.40 to 1.28.
  
  
  CONCLUSIONS
  Osteoarthritic knees that progressed had less toeing-out than knees without progression. Greater toe-out was associated with a lower likelihood of progression. Adjustment for covariates did not alter the OR, although the 95% CI included 1. Further adjustment for adduction moment did alter the OR, consistent with the possibility that a mechanism of the effect may be via lowering of the adduction moment.
authors.affiliation: Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
authors.forename: Alison
authors.initials: A
authors.lastname: Chang
authors.forename: Debra
authors.initials: D
authors.lastname: Hurwitz
authors.forename: Dorothy
authors.initials: D
authors.lastname: Dunlop
authors.forename: Jing
authors.initials: J
authors.lastname: Song
authors.forename: September
authors.initials: S
authors.lastname: Cahue
authors.forename: Karen
authors.initials: K
authors.lastname: Hayes
authors.forename: Leena
authors.initials: L
authors.lastname: Sharma
mesh_terms: D000368:Aged; D018450:Disease Progression; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology; D008297:Male; D020370:Osteoarthritis, Knee / Q000503:physiopathology*; D011187:Posture / Q000502:physiology; D014034:Toes / Q000473:pathology* / Q000503:physiopathology