ABSTRACT
OBJECTIVES: To assess the construct validity and responsiveness of these performance-based tests in individuals with knee osteoarthritis (KOA). DESIGN: This study has a prospective cohort design. SETTING: Assessments were administered at the Federal University of São Carlos (Brazil) by three different raters. PARTICIPANTS: A total of 107 participants with KOA were aged 40 and over. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: This study assessed the construct validity and responsiveness of three performance-based tests: 40m Fast-Paced Walk Test, 11-step Stair Climb Test, 30-second Chair Stand Test (40m FPWT, 11-step SCT, and 30-s CST, respectively). The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Knee Injury and Osteoarthritis Outcome Score (KOOS), sedentary behavior (ActivPAL), and numeric pain rating scale (NPRS) were used as comparator instruments. Measurements were obtained at baseline and after 6 months. The construct validity and responsiveness were calculated using Spearman's correlation coefficient within predefined hypotheses based on a panel comprising five experts in the field of outcome measurement in KOA. RESULTS: The three performance-based tests showed excellent (ICC > 0.9) reliability (intra and inter); however, only the 40m FPWT and 11-SCT were considered valid and responsive, as both confirmed more than 75% of the priori hypotheses. The 30-s CST was not considered valid or responsive as it has not confirmed at least 75% of the priori hypotheses. CONCLUSION: The three performance-based tests are reliable for intra and inter assessments. The 40m FPWT and 11-step SCT are both valid and responsive for measuring physical function in patients with KOA. The 30-s CST was not considered valid or responsive. Therefore, 40m FPWT and 11-step SCT can detect changes over time and are indicated for functional assessment in clinical practice.
