title: A new approach yields high rates of radiographic progression in knee osteoarthritis.
abstract: OBJECTIVE
  Progression of knee osteoarthritis (OA) has typically been assessed in the medial tibiofemoral (TF) compartment on the anteroposterior (AP) or posteroanterior (PA) view. We propose a new approach using multiple views and compartments that is likely to be more sensitive to change and reveals progression throughout the knee.
  
  
  METHODS
  We tested our approach in the Multicenter Osteoarthritis Study, a study of persons with OA or at high risk of disease. At baseline and 30 months, subjects provided PA (fixed flexion without fluoro) and lateral weight-bearing knee radiographs. Paired radiographs were read by 2 readers who scored joint space (JS) using a 0-3 atlas-based scale. When JS narrowed but narrowing did not reach a full grade on the scale, readers used half-grades. Change was scored in medial and lateral TF compartments on both PA and lateral views and in the patellofemoral (PF) joint on lateral view. A knee showed progression when there was at least a half-grade worsening in JS width in any compartment at followup. Disagreements were adjudicated by a panel of 3 readers. To validate progression, we tested definitions for TF progression to see if malalignment on long-limb radiographs at baseline (>or=3 degrees malaligned in any direction with nonmalaligned knees being reference) increased risk of progression. A valid definition of progression would show that malalignment strongly predicted progression.
  
  
  RESULTS
  We studied 842 knees with either Kellgren-Lawrence grade>or=2 or PF OA at baseline in 606 subjects (age range 50-79 yrs, mean 63.9 yrs; 66.6% women). Mean body mass index was 31.9, and 32.8% of knees had frequent knee pain at baseline. Of these, 500 knees (59.4%) showed progression. Of the 500, 75 (15%) had progression only in the PF joint, while the remainder had progression in the TF joint. Malalignment increased the risk of overall progression in TF joint and increased the risk of half-grade progression, suggesting that half-grade progression had validity.
  
  
  CONCLUSIONS
  PA and lateral views obtained in persons at high risk of OA progression can produce a cumulative incidence of progression above 50% at 30 months. Keys to increasing the yield include imaging PF and lateral compartments, using semiquantitative scales designed to detect change, and examining more than one radiographic view.
authors.affiliation: Clinical Epidemiology Research and Training Unit, Boston University School of Medicine, and Department of Radiology, Brigham and Women's Hospital, Boston, Massachusetts 02118, USA. dfelson@bu.edu
authors.forename: David T
authors.initials: DT
authors.lastname: Felson
authors.forename: Michael C
authors.initials: MC
authors.lastname: Nevitt
authors.forename: Mei
authors.initials: M
authors.lastname: Yang
authors.forename: Margaret
authors.initials: M
authors.lastname: Clancy
authors.forename: Jingbo
authors.initials: J
authors.lastname: Niu
authors.forename: James C
authors.initials: JC
authors.lastname: Torner
authors.forename: C Elizabeth
authors.initials: CE
authors.lastname: Lewis
authors.forename: Piran
authors.initials: P
authors.lastname: Aliabadi
authors.forename: Burton
authors.initials: B
authors.lastname: Sack
authors.forename: Charles
authors.initials: C
authors.lastname: McCulloch
authors.forename: Yuqing
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D000368:Aged; D018450:Disease Progression; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging*; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging*; D011859:Radiography
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