Quality of Life Research

, Volume 22, Issue 9, pp 2561–2568 | Cite as

Can pain and function be distinguished in the Oxford Knee Score in a meaningful way? An exploratory and confirmatory factor analysis

  • Kristina HarrisEmail author
  • Jill Dawson
  • Helen Doll
  • Richard E. Field
  • David W. Murray
  • Raymond Fitzpatrick
  • Crispin Jenkinson
  • Andrew J. Price
  • David J. Beard



The purpose of this paper was to examine if pain and functioning can be distinguished in the Oxford Knee Score (OKS) in a meaningful way. This was done by (1) conducting exploratory factor analysis to explore the factorial structure of the OKS and (2) conducting confirmatory factor analysis to examine whether a two-factor solution is superior to a one-factor solution.


Secondary data analysis of four independent datasets containing OKS scores on 161,973 patients was performed. Four independent datasets contained data on: (1) 156, 788 patients from the NHS HES/PROMS dataset, (2) 2,405 consecutive patients from the South West London Elective Operating Centre, (3) 2,353 patients enrolled in the Knee Arthroplasty Trial and (4) 427 consecutive patients listed for knee replacement surgery at the Nuffield Orthopaedic Centre in Oxford.


Factor extraction methods suggested that, depending on the method employed, both one- and two-factor solutions are meaningful. Overall and in each data set some cross-loading occurred and item loadings were consistent across two factors. On confirmatory factor analysis, both one- and two-factor models had acceptable fit indices. This allowed the creation of the ‘OKS pain component’ and the ‘OKS functional component’ subscales.


Factor analysis confirmed the original conceptual basis of the OKS but offered an option to perform additional analyses using pain and functional subscales. Further research should focus on providing further evidence on construct validity and responsiveness of the newly derived subscales.


Patient-reported outcomes Osteoarthritis Total joint replacement Outcomes assessment 



A copy of the OKS questionnaire and permission to use this measure can be acquired from Isis Innovation Ltd, the technology transfer company of the University of Oxford via website: or email: Authors at the Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences thank the NIHR Biomedical Research Unit for its support. The KAT dataset was reused with the permission of the KAT Project Management Group.

Supplementary material

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Supplementary material 1 (DOCX 21 kb)


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Copyright information

© Springer Science+Business Media Dordrecht 2013

Authors and Affiliations

  • Kristina Harris
    • 1
    Email author
  • Jill Dawson
    • 2
  • Helen Doll
    • 3
  • Richard E. Field
    • 4
  • David W. Murray
    • 1
  • Raymond Fitzpatrick
    • 2
  • Crispin Jenkinson
    • 2
  • Andrew J. Price
    • 1
  • David J. Beard
    • 1
  1. 1.Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal SciencesUniversity of OxfordOxfordUK
  2. 2.Department of Public HealthUniversity of OxfordOxfordUK
  3. 3.Norwich Medical SchoolUniversity of East AngliaNorwichUK
  4. 4.South West London Elective Orthopaedic CentreSurreyUK

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