title: Validity and sensitivity to change of three scales for the radiographic assessment of knee osteoarthritis using images from the Multicenter Osteoarthritis Study (MOST).
abstract: OBJECTIVE
  The purpose of this study was to assess the concurrent validity and sensitivity to change of three knee osteoarthritis (OA) grading scales. The Kellgren-Lawrence (KL) and the Osteoarthritis Research Society International (OARSI) joint space narrowing (JSN) grading scales are well-established. The third scale, the compartmental grading scale for OA (CG) is a novel scale which grades JSN, femoral osteophytes, tibial erosion and subluxation to create a total score.
  
  
  METHODS
  One sample of 72 posteroanterior (PA) fixed-flexion radiographs displaying mild to moderate knee OA was selected from the Multicenter Osteoarthritis Study (MOST) to study validity. A second sample of 75 radiograph pairs, which showed an increase in OA severity over 30 months, was selected to study sensitivity to change. The three radiographic grading scales were applied to each radiograph in both samples. Spearman's rank correlation coefficients were used to correlate the radiographic grades and the change in grades over 30 months with a Whole-organ Magnetic Resonance Imaging Score (WORMS)-based composite score which included five articular features of knee OA.
  
  
  RESULTS
  Correlations between the KL, OARSI JSN and CG grading scales and the magnetic resonance image (MRI)-based score were 0.836, 0.840 and 0.773 (P < 0.0001) respectively while correlations between change in the radiographic grading scales and change in the MRI-based score were 0.501, 0.525 and 0.492 (P < 0.0001).
  
  
  CONCLUSIONS
  All three radiographic grading scales showed high validity and are suitable to assess knee OA severity. They showed moderate sensitivity to change; therefore caution should be taken when using ordinal radiographic grading scales to monitor knee OA over time.
authors.affiliation: Bruyère Research Institute, Ottawa, ON, Canada; School of Rehabilitation Sciences, University of Ottawa, Ottawa, ON, Canada. Electronic address: lsheehy@bruyere.org.
authors.forename: L
authors.initials: L
authors.lastname: Sheehy
authors.affiliation: School of Rehabilitation Therapy, Queen's University, Kingston, ON, Canada. Electronic address: elsie.culham@queensu.ca.
authors.forename: E
authors.initials: E
authors.lastname: Culham
authors.affiliation: School of Rehabilitation Sciences, University of Ottawa, Ottawa, ON, Canada. Electronic address: mcleanl@queensu.ca.
authors.forename: L
authors.initials: L
authors.lastname: McLean
authors.affiliation: Boston University School of Medicine, Boston, MA, USA. Electronic address: niujp@bu.edu.
authors.forename: J
authors.initials: J
authors.lastname: Niu
authors.affiliation: Department of Epidemiology and Biostatistics, University of California, San Francisco, CA, USA. Electronic address: JLynch@psg.ucsf.edu.
authors.forename: J
authors.initials: J
authors.lastname: Lynch
authors.affiliation: Department of Rehabilitation Medicine, University of Kansas, Kansas City, KS, USA; Department of Epidemiology, University of Iowa, Iowa City, IA, USA. Electronic address: neil-segal@uiowa.edu.
authors.forename: N A
authors.initials: NA
authors.lastname: Segal
authors.affiliation: Department of Medicine at School of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA; Division of Epidemiology at School of Public Health, University of Alabama at Birmingham, Birmingham, AL, USA; Medicine Service, VA Medical Center, Birmingham, AL, USA; Department of Orthopedic Surgery, Mayo Clinic College of Medicine, Rochester, MN, USA. Electronic address: jasvinder.md@gmail.com.
authors.forename: J A
authors.initials: JA
authors.lastname: Singh
authors.affiliation: Department of Epidemiology and Biostatistics, University of California, San Francisco, CA, USA. Electronic address: MNevitt@psg.ucsf.edu.
authors.forename: M
authors.initials: M
authors.lastname: Nevitt
authors.affiliation: School of Rehabilitation Therapy, Queen's University, Kingston, ON, Canada. Electronic address: derek@cookes.ca.
authors.forename: T D V
authors.initials: TD
authors.lastname: Cooke
mesh_terms: D005260:Female; D006801:Humans; D007717:Knee / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging*; D011859:Radiography; D015203:Reproducibility of Results; D012720:Severity of Illness Index
keywords: Grading; Knee osteoarthritis; Knee radiographs; Sensitivity to change; Validity