title: Proximal femur shape differs between subjects with lateral and medial knee osteoarthritis and controls: the Osteoarthritis Initiative.
abstract: OBJECTIVE
  This study examined the association of proximal femur shape with ipsilateral medial and lateral compartment knee osteoarthritis (OA).
  
  
  METHODS
  Radiographs were obtained from the NIH-funded Osteoarthritis Initiative (OAI). Cases of isolated radiographic lateral compartment knee OA were defined on baseline radiographs as Kellgren/Lawrence (K/L) Grade ≥ 2 and joint space narrowing (JSN) > 0 in the lateral compartment and JSN = 0 in the medial compartment; isolated medial compartment knee OA had K/L ≥ 2 and JSN > 0 medially with JSN = 0 in the lateral compartment. Controls had K/L < 2 and JSN = 0 in both compartments. Controls were frequency matched to cases by sex and 10-year age intervals. We characterized the shape of the proximal femurs on radiographs using Active Shape Modeling (ASM) and determined the association of proximal femur shape with knee OA using logistic regression.
  
  
  RESULTS
  There were 168 lateral compartment knee OA cases (mean body mass index (BMI) 29.72 ± 5.26), 169 medial compartment knee OA cases (mean BMI 29.68 ± 4.83) and 168 controls (mean BMI 26.87 ± 4.2). Thirteen modes were derived for femur shape which described 95.5% of the total variance in proximal femur shape in the population. Modes 6, 8 and 12 were associated with prevalent lateral compartment knee OA. Medial compartment knee OA was associated with proximal femur modes 1, 5, 8, and 12.
  
  
  CONCLUSIONS
  Prevalent lateral and medial compartment knee OA are associated with different ipsilateral proximal femur shapes. Additional studies are needed to better define how the shape of the proximal femur influences compartment-specific knee OA.
authors.affiliation: Department of Internal Medicine, University of California, Davis School of Medicine, Sacramento, CA, USA. Electronic address: barton.wise@ucdmc.ucdavis.edu.
authors.forename: B L
authors.initials: BL
authors.lastname: Wise
authors.affiliation: Department of Internal Medicine, University of California, Davis School of Medicine, Sacramento, CA, USA.
authors.forename: L
authors.initials: L
authors.lastname: Kritikos
authors.affiliation: Department of Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, CA, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Lynch
authors.affiliation: Department of Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, CA, USA.
authors.forename: F
authors.initials: F
authors.lastname: Liu
authors.affiliation: San Francisco Coordinating Center, California Pacific Medical Center Research Institute, San Francisco, CA, USA.
authors.forename: N
authors.initials: N
authors.lastname: Parimi
authors.affiliation: Department of Orthopaedic Surgery, Stanford University School of Medicine, Palo Alto, CA, USA.
authors.forename: K L
authors.initials: KL
authors.lastname: Tileston
authors.affiliation: Department of Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, CA, USA.
authors.forename: M C
authors.initials: MC
authors.lastname: Nevitt
authors.affiliation: Department of Internal Medicine, University of California, Davis School of Medicine, Sacramento, CA, USA.
authors.forename: N E
authors.initials: NE
authors.lastname: Lane
mesh_terms: D005260:Female; D005269:Femur / Q000033:anatomy & histology*; D006621:Hip Joint / Q000033:anatomy & histology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000473:pathology*
keywords: Compartment; Hip; Knee; Osteoarthritis; Shape