Basar S, et al. – The purpose of this study was to examine the cultural adaptation, validity, and reliability of Western Ontario Shoulder Instability Index (WOSI) in Turkish population with shoulder disability. Findings confirmed that the Turkish version of WOSI was a valid and reliable scale to determine the final condition of the patients with shoulder disabilities.

• WOSI was translated and culturally adapted from English into Turkish.
• Test–retest analyses were conducted to evaluate the level of reliability and internal consistency.
• Reliability (test–retest) analyses were performed by means of retest 72 h later with a sub–group of 30 patients.
• Construct validity of the WOSI was checked through convergent validity with Disabilities of Arm, Shoulder and Hand Scale, Rowe Score Questionnaire, Oxford Shoulder Instability Questionnaire, and Western Ontario Rotator Cuff Index by 60 patients with shoulder instability.
• In investigations, the Turkish version of the questionnaire displayed high internal consistency (0.77–0.91) with a Cronbach’s Alpha value of 0.91.
• As for the test–retest reliability, the ICC value was found to be high (95% CI 0.97).
• Floor and ceiling effects (15%) were observed neither in sub–parameters (0–4.9%) nor in total score (0%).
• WOSI total score was found to have a negative good correlation with the Rowe Score (r = –0.57) and a very good–excellent correlation with other questionnaires (r = 0.67–0.89).