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*292. Evaluating Knee Specific Pain and Satisfaction with Knee Procedure: A Validation Study

K Wristers, Houston Center for Quality of Care and Utilization Studies; Baylor College of Medicine, Section of Health Services Research; NP Wray, Houston Center for Quality of Care and Utilization Studies; Baylor College of Medicine, Section of Health Services Research; AJ Greisinger, Houston Center for Quality of Care and Utilization Studies; Baylor College of Medicine, Section of Health Services Research; JB Mosely, Department of Orthopedic Surgery, Baylor College of Medicine; NJ Petersen, Houston Center for Quality of Care and Utilization Studies; Baylor College of Medicine, Section of Health Services Research; TJ Menke, Houston Center for Quality of Care and Utilization Studies; Baylor College of Medicine, Section of Health Services Research

Objectives: Knee pain due to Osteoarthritis (OA) is a common cause of disability in the elderly. Studies have reported that knee arthroscopy improves knee pain due to OA, however all of these studies fail to control for the placebo effect. To evaluate whether the effect of knee arthroscopy is greater than placebo, we conducted a randomized, double blind, placebo-controlled trial comparing arthroscopic debridement plus lavage to arthroscopic lavage only or placebo surgery. Critical tools for our trial were measures of knee pain and satisfaction with the knee procedure. While generic measures of these constructs existed, researchers have reported that they are not very responsive to change. We needed symptom-specific measures that were sensitive enough to detect clinically meaningful changes in pain and satisfaction. The study's objective, therefore, was to create and psychometrically test knee-specific measures of pain in the study knee and satisfaction with knee procedure.

Methods: We created the six-item Knee Specific Pain Scale (KSPS) to assess current level, intensity, and distress associated with pain in the study knee. We also created the four-item Satisfaction with Knee Procedure (SkiP) scale to assess patients' agreement with statements such as "I feel the operation was worthwhile". Both scales had Likert-style response categories with five choices that ranged from strongly agree to strongly disagree. Scores on both the KSPS and the SKiP ranged from 0 to 100, with higher scores representing more pain and more satisfaction, respectively. Data collected on eight occasions over two years from 180 patients were used in this study. Principal components factor analyses were used to evaluate the factor structure of each scale. The intraclass correlation coefficient was used to estimate test-retest reliability of the scales over all eight occasions. We compared the KSPS and SKiP to the SF-36 subscales, the AIMS 2 subscales, and three measures of satisfaction to gather evidence for validity. We evaluated whether the KSPS and SKiP were sensitive to change by comparing patients' initial scores to their final scores using paired-samples t-tests.

Results: Factor analytic results provided evidence that each scale was unidimensional. Test-retest reliability was estimated as .76 for the KSPS and .96 for the SKiP. The KSPS correlated highest with the other pain measures (.56 -.76) and the SKiP correlated highest with the other measures of satisfaction (.46- .58) providing evidence for validity. Both the KSPS and the SKiP demonstrated excellent evidence for responsiveness, since patients' pain and satisfaction scores significantly changed over the course of the trial (p < .001).

Conclusions: The Knee Specific Pain Scale and the Satisfaction with Knee Procedure Scale are reliable, valid, and responsive scales for use with patients receiving treatment for osteoarthritis of the knee.

Impact: Many generic pain and satisfaction measures with excellent psychometric properties exist, however, generic measures are typically less responsive than symptom-specific measures. To most effectively and comprehensively evaluate patients' response to treatment, researchers should use both generic and symptom-specific measures. The scales developed in this study are excellent measures for detecting pain and satisfaction changes in patients receiving arthroscopy for OA of the knee.