Objective: To test the validity and reliability of arabic-language version of the knee injury and osteoarthritis outcome score physical function short form to measure the physical function in knee osteoarthritic patients. Method: Sixty nine patients with knee osteoarthritis (bilateral osteoarthritis considered 2 cases) were recruited and 150 sheets (test and retest sheets) were filled out and three expert panels (each consists of ten experts) participated in this study, forward translation, development of preliminary initially translated version, backward translation, development of the pre-final version and testing of pre-final version using experts then testing of the final version on patients was done. Clarity index, expert proportion of clearance, index of content validity, expert proportion of relevance, descriptive statistics, missed item index, Cronbach’s alpha and Spearman’s rank correlation coefficient were used for statistical analysis. Results: The study showed that scale index of clarity equals 100%, scale-level clarity index universal agreement equals 100%, scale index of content validity equals 97.14%, scale-level content validity index universal agreement equals 71%, the scale items were filled by 99.4% in all sheets, the scale needed less than five minutes to answer in about 99% all sheets, Cronbach's alpha equals 0.848 (0.789, 0.896) and all Spearman’s correlations between test and retest results were statistically significant. Conclusion: Arabic-language version of the knee injury and osteoarthritis outcome score physical function short form is valid and reliable enough to measure the physical function in knee osteoarthritic patients.
