Cross-cultural adaptation of the Greek version of the Knee Outcome Survey – Activities of Daily Living Scale (KOS-ADLS)

Abstract

The purpose of this study was to cross-culturally adapt and validate the Greek version of Knee Outcome Survey-Activities of Daily Living Scale (KOS-ADLS), a self-reported instrument used for patients with various knee pathological conditions including osteoarthritis. Ninety-four patients (57 males and 37 females) with a variety of pathological knee disorders and impairments being referred to physical therapy for evaluation and treatment were included in the study. For the crοss-cultural translation, a back-translation procedure was utilized by 3 bi-lingual translators. To assess test–retest reliability the patients were asked to complete the KOS-ADLS twice at initial visit; before and after physiotherapy treatment. To assess responsiveness, patients completed the KOS-ADLS at the end of all physiotherapy sessions and the score was compared with KOS-ADLS at initial (pre-treatment) visit. Finally, concurrent validity was measured by comparing the responses to the KOS-ADLS scores against the scores obtained from Visual Analogue Scale (VAS) and Global Rating Scale (GRS). Reliability was found satisfactory (ICC = 0.97; SEM = 3.03; SDD = 23.05; Cronbach's alpha = 0.98). Moreover, a gender subgroup analysis showed that women were more reliable than men. Minor floor/ceiling effects were detected. Concerning validity, all correlations were statistically significant, ranging from r = 0.315 to r = 0.741, however GRS presented higher correlations with KOS-ADLS in comparison with VAS. Finally, Greek KOS-ADLS was able to detect changes over time (standardized effect size = 1.31 and standardized response mean = 1.64). The Greek version of KOS-ADLS was found to be reliable, valid, responsive and comprehensible to use with patients with knee pathology.