Clinical Rheumatology

, Volume 37, Issue 4, pp 1091–1098 | Cite as

Can we have an overall osteoarthritis severity score for the patellofemoral joint using magnetic resonance imaging? Reliability and validity

  • Sarah Kobayashi
  • Anthony Peduto
  • Milena Simic
  • Marlene Fransen
  • Kathryn Refshauge
  • Jean Mah
  • Evangelos Pappas
Original Article


This work aimed to assess inter-rater reliability and agreement of a magnetic resonance imaging (MRI)-based Kellgren and Lawrence (K&L) grading for patellofemoral joint osteoarthritis (OA) and to validate it against the MRI Osteoarthritis Knee Score (MOAKS). MRI scans from people aged 45 to 75 years with chronic knee pain participating in a randomised clinical trial evaluating dietary supplements were utilised. Fifty participants were randomly selected and scored using the MRI-based K&L grading using axial and sagittal MRI scans. Raters conducted inter-rater reliability, blinded to clinical information, radiology reports and other rater results. Intra- and inter-rater reliability and agreement were evaluated using the intra-class correlation coefficient (ICC) and Cohen’s weighted kappa. There was a 2-week interval between the first and second readings for intra-rater reliability. Validity was assessed using the MOAKS and evaluated using Spearman’s correlation coefficient. Intra-rater reliability of the K&L system was excellent: ICC 0.91 (95% CI 0.82–0.95); weighted kappa (ĸ = 0.69). Inter-rater reliability was high (ICC 0.88; 95% CI 0.79–0.93), while agreement between raters was moderate (ĸ = 0.49–0.57). Validity analysis demonstrated a strong correlation between the total MOAKS features score and the K&L grading system (ρ = 0.62–0.67) but weak correlations when compared with individual MOAKS features (ρ = 0.19–0.61). The high reliability and good agreement show consistency in grading the severity of patellofemoral OA with the MRI-based K&L score. Our validity results suggest that the scale may be useful, particularly in the clinical environment. Future research should validate this method against clinical findings.


Bone Cartilage Diagnostic imaging Knee Magnetic resonance imaging Osteoarthritis 


Funding information

The MRI scans that were used for this manuscript came from the Longitudinal Evaluation of Glucosamine Sulphate (LEGS) trial, which was funded by the National Health and Medical Research Council of Australia (ID 402511), the Department of Health and Ageing (Australia) (ID 402781) and by some supplementary funding (< 15% total) from Sanofi-Aventis Consumer Healthcare Pty Ltd., Australia. The funders had no role in the design of the study; collation, analysis or interpretation of the data or preparation, review or approval of the manuscript.

Compliance with ethical standards

The study is in accordance with the Declaration of Helsinki and it was approved by the local human research ethics committee.



Supplementary material

10067_2017_3888_MOESM1_ESM.pdf (4.4 mb)
ESM 1 (PDF 4542 kb).


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Copyright information

© International League of Associations for Rheumatology (ILAR) 2017

Authors and Affiliations

  • Sarah Kobayashi
    • 1
  • Anthony Peduto
    • 2
  • Milena Simic
    • 1
  • Marlene Fransen
    • 1
  • Kathryn Refshauge
    • 1
  • Jean Mah
    • 3
  • Evangelos Pappas
    • 1
  1. 1.Faculty of Health Sciences, Discipline of PhysiotherapyUniversity of SydneySydneyAustralia
  2. 2.Department of Radiology Westmead Hospital and Western Clinical School, Discipline of Medical Imaging, Sydney Medical SchoolUniversity of SydneySydneyAustralia
  3. 3.Department of ImagingWestmead HospitalWestmeadAustralia

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