Development of the Persian Version of Knee Outcome Survey Activities for Daily Living Scale

Background: The knee outcome survey-activities of daily living (KOS-ADL) scale is a self-reported measure to determine knee function and symptoms in individuals suffering from a variety of knee disorders. The present study aimed to assess the validity, reliability, and cross-cultural adaptation of the Persian version of the KOS-ADL scale. Methods: In this cross-sectional and psychometric study, 130 patients (14 men and 116 women) with different grades of knee osteoarthritis were recruited. The construct validity of the scale was examined through the correlation between the domains of KOS-ADL and the subclasses of the knee injury and osteoarthritis outcome score (KOOS). To assess the test-retest reliability, 40 of the participants were requested to fill in the questionnaire again with an 8-day interval. The internal consistency of the questionnaire and its subclasses was evaluated with Cronbach’s alpha coefficient. To evaluate construct validity, concurrent construct validity was examined with a correlation matrix using Pearson’s correlation coefficients between the KOS-ADL domains and KOOS total score and subclasses. The test-retest reliability was analyzed using the intra-class correlation coefficient (ICC). The Kappa coefficient was used to determine the intra-rater agreement. Results: The Persian version of the KOS-ADL scale had good reliability (ICC=0.79) and internal consistency (α=0.92). There was a good correlation between the KOS-ADL total score and KOOS subclasses (r≥0.71, P≤0.001). Conclusion: The Persian version of the KOS-ADL scale is a valid and reliable instrument to evaluate the symptoms and functional status of people suffering from knee osteoarthritis.