Background:It is well known that questionnaires and scales are easy to use, cheap, and provide fast results. In the clinical setting, it will be easier and more comfortable to evaluate lower-extremity functions in both prosthesis and orthosis users with a single questionnaire.Objectives:To study the Turkish version of the orthotics and prosthetics users' survey lower-extremity functional status (OPUS-LEFS) and investigate its reliability and validity in the Turkish prosthesis and orthosis users.Study design:After forward and backward translation process, test-retest, internal consistency, validity, dimensionality, and Rasch analysis were done for 139 participants.Methods:Participants with a lower-limb prosthesis or orthosis were recruited in this study. Test and retest of the survey was done 1-3 days apart. For convergent validity, Nottingham Health Profile was used. Pearson correlation coefficient was used to analyze test-retest reliability; Cronbach's alpha for internal consistency, Spearman's correlation coefficient for validity, exploratory factor analysis by means of Kaiser-Meyer-Olkin and Bartlett's value of sphericity for dimensionality, and Rasch analysis were used.Results:Test-retest reliability of OPUS-LEFS showed very strong correlation (0.994) and for internal consistency with Cronbach's alpha value 0.71 of the Turkish version of OPUS-LEFS. Analyses showed that OPUS-LEFS is valid (p < 0.001) and significant (p < 0.001).Conclusions:The Turkish version of the OPUS-LEFS has been shown to be a valid and reliable tool in evaluating both orthosis and prosthesis users with a self-administered questionnaire for LEFS.