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J Clin Epidemiol. 2006 Jul;59(7):724-31.

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

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  • 1Institute for Research in Extramural Medicine, VU University Medical Center, van der Boechorststraat 7, Amsterdam 1081 BT, The Netherlands. cb.terwee@vumc.nl

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.

PMID:
16765276
[PubMed - indexed for MEDLINE]
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