Dunbar MJ, Robertsson O, Ryd L.

What's all that noise? The effect of co-morbidity on health outcome questionnaire results after knee arthroplasty.

Acta Orthop Scand. 2004 Apr;75(2):119-26.

We modified the Charnley Classification for hips to facilitate its use with knee arthroplasty patients and investigated what affect the different classes of co-morbidity had on the results of a spectrum of outcome questionnaires. PATIENTS AND METHODS: 3600 patients from the Swedish Knee Arthroplasty Registry were surveyed by post with a variety of questionnaires ranging from multiple-item general health, to a single-item knee arthroplasty specific questionnaire. All patients also completed a co-morbidity questionnaire, from which a modified Charnley Classification was generated for each patient. We then investigated the correlation and relationship between the results of the questionnaires and the different classes of co-morbidity. RESULTS: The results of the questionnaires tested varied significantly by Charnley Class, regardless of the specificity of the questionnaire used. INTERPRETATION: We suggest that co-morbidity should be taken into account in outcome studies utilizing general health or disease/site specific questionnaires.
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