title: Varus-valgus alignment in the progression of patellofemoral osteoarthritis.
abstract: OBJECTIVE
  To test the hypotheses that lateral patellofemoral (PF) osteoarthritis (OA) progression is more common than medial PF OA progression, that varus alignment increases the likelihood of medial PF OA progression, and that valgus alignment increases the likelihood of lateral PF OA progression.
  
  
  METHODS
  Patients with knee OA were recruited from the community. Inclusion criteria were definite osteophyte presence (i.e., Kellgren/Lawrence radiographic grade >/=2) in 1 or both knees and at least some difficulty with knee-requiring activity. Varus-valgus alignment (the angle formed by the intersection of the mechanical axes of the femur and tibia) was measured on a full-limb radiograph at baseline. To assess PF OA progression, weight-bearing skyline views of the PF compartment were obtained at baseline and at 18-month followup. Knees with the highest grade of PF narrowing at baseline were excluded from analysis. Logistic regression and generalized estimating equations were used; odds ratios (ORs) were adjusted for age, sex, and body mass index.
  
  
  RESULTS
  Lateral PF OA progression, which occurred in 120 (30%) of 397 knees, was more common than was medial PF OA progression, which occurred in 60 knees (15%). Varus (versus nonvarus) alignment increased the odds of PF OA progression isolated to the medial PF compartment (adjusted OR 1.85, 95% confidence interval [95% CI] 1.00-3.44). Valgus alignment increased the odds of PF OA progression isolated to the lateral compartment (adjusted OR 1.64, 95% CI 1.01-2.66).
  
  
  CONCLUSIONS
  Lateral PF OA progression was more common than medial progression, and varus-valgus alignment influenced the likelihood of PF OA progression in a compartment-specific manner. Interventions that address the stress imposed by alignment on the PF compartments may delay PF OA progression and should be developed.
authors.affiliation: Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA.
authors.forename: September
authors.initials: S
authors.lastname: Cahue
authors.forename: Dorothy
authors.initials: D
authors.lastname: Dunlop
authors.forename: Karen
authors.initials: K
authors.lastname: Hayes
authors.forename: Jing
authors.initials: J
authors.lastname: Song
authors.forename: Leah
authors.initials: L
authors.lastname: Torres
authors.forename: Leena
authors.initials: L
authors.lastname: Sharma
mesh_terms: D000368:Aged; D001175:Arthrography; D017760:Bone Malalignment / Q000000981:diagnostic imaging*; D018450:Disease Progression; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging*; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging*; D016013:Likelihood Functions; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging*; D010329:Patella / Q000000981:diagnostic imaging*; D012720:Severity of Illness Index