Reliability, validity and responsiveness of the Icelandic version of the knee injury and osteoarthritis outcome score (KOOS)

Purpose: The KOOS self-report questionnaire (Knee injury and Osteoarthritis Outcome Score) has 5 sub-scales, assessing knee symptoms and function, and quality of life. It is widely used as it has been found to be a valid and reliable measure. The purpose of this study was to investigate the validity, reliability and responsiveness of the Icelandic translation of KOOS. Methods: A total of 145 were recruited for the study and in addition to answering KOOS, knee pain was rated on a visual analog scale (VAS), perception of knee function during activities of daily living on a numerical rating scale, and some were tested with the timed up-and-go test (TUG). Reliability was assessed by observing ICC-values, internal consistency with Cronbach's alpha, and associations between KOOS subscales and other outcome measures with Pearson's correlation coefficient. A one-way ANOVA was used to assess differences between groups of participants with different levels of knee dysfunction. Results: A significant change in all KOOS subscales was found in a group of individuals seeking treatment for their knee dysfunction (p < 0.001), while no change was seen in a group reporting stable knee status (ICC-values ranging from 0.825 to 0.930). Cronbach's alpha ranged from 0.726 to 0.966 and significant correlations were found between all KOOS sub-scales and other outcome measures (p < 0.001). Conclusion: The results indicate that the Icelandic version of KOOS is a valid and reliable measure that may be used as an outcome measure assessing knee symptoms and function of individuals with knee symptoms and impaired knee function.