Self-reported physical functioning was more influenced by pain than performance-based physical functioning in knee-osteoarthritis patients

Caroline B. Terwee*, Rienk M.A. van der Slikke, Rob C. van Lummel, Rob J. Benink, Wil G.H. Meijers, Henrica C.W. de Vet

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Background and Objectives: To test the hypothesis that self-reported physical functioning is more influenced by pain than performance-based physical functioning. Methods: 163 knee-osteoarthritis patients completed the performance-based DynaPort® KneeTest (DPKT), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and SF-36 (self-report measures of pain and physical functioning) before, 3, 6, and 12 months after knee replacement. Results: Correlations between (two) self-reported measures of functioning and (two) pain measures were higher (0.57-0.74) than correlations between the performance-based measure of functioning and the two pain measures (0.20 and 0.26). In factor analysis, WOMAC and SF-36 pain and physical functioning subscores loaded on the first factor (eigenvalue 3.2), while DPKT KneeScore2 loaded on the second factor (eigenvalue 0.92). Before surgery, correlations between performance-based and self-reported physical functioning were higher in patients with less pain (0.43) compared to patients with more pain (0.17), for the WOMAC (as expected), but not for the SF-36. After surgery, when the pain had diminished, the correlations between performance-based and self-reported physical functioning were higher, especially for the WOMAC. Conclusions: Our hypothesis was convincingly supported by the results of the WOMAC, and somewhat less by the results of the SF-36. We consider this as evidence for a lack of content validity of the WOMAC.

Original languageEnglish
Pages (from-to)724-731
Number of pages8
JournalJournal of Clinical Epidemiology
Volume59
Issue number7
DOIs
Publication statusPublished - 1 Jul 2006

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