Persian translation and validation of the Kujala Patellofemoral Scale in patients with patellofemoral pain syndrome.

Abstract

To culturally translate and validate the Persian version of Kujala Patellofemoral Scale (KPS) and evaluate the test-retest reliability, internal consistency, construct validity and ceiling or floor effects of this instrument in patients with patellofemoral pain syndrome (PFPS). After standard forward and backward translations, 100 patients with PFPS completed the Persian versions of the KPS and Short-Form 36 Health Survey (SF-36) in the first visit. With time interval of 2-3 days after the first visit, 47 patients filled out the KPS in the second visit. Test-retest reliability and internal consistency were assessed using intraclass correlation coefficient (ICC(2,1)) with 95% confidence interval (95% CI) and Cronbach's α coefficient, respectively. The Spearman's rank correlation (r(s)) was used to assess the correlations between the Persian KPS and SF-36 subscales. The acceptable level of ICC >0.70 (ICC = 0.96, 95% CI = 0.93-0.98) and Cronbach's α coefficient >0.70 (α = 0.81) was obtained for the Persian KPS. There were low to moderate correlations (r(s) = 0.25-0.60, p < .01) between the Persian KPS and Persian SF-36 subscales of mental and physical health components. However, correlations between the Persian KPS and SF-36 physical components were higher than correlations between the Persian KPS and SF-36 mental components. No ceiling and floor effects were seen for the Persian KPS. The Persian version of KPS is a reliable and valid outcome measure of disability and seems to be a suitable instrument for use in clinical practice of Iranian patients with chronic PFPS.