One of the self-assessment tools used in shoulder instability to evaluate patient's quality of life is the Western Ontario Shoulder Instability (WOSI) Index. It is a valid and reliable disease-specific tool that has been translated into many languages. The aim of this study is to cross-culturally adapt the Western Ontario Shoulder Instability (WOSI) Index into Arabic and assess its psychometric properties in patients diagnosed with shoulder instability in order to help surgeons and physical therapists assess patients following an intervention.

Forty-four patients with shoulder instability participated in the study. For validity and reliability, the WOSI, Disability of Arm, Shoulder and Hand questionnaire (DASH) and the American Shoulder and Elbow Surgeons (ASES) questionnaire were completed at baseline and the WOSI again within 1 week. For responsiveness the WOSI was completed 1 week postoperative and again 6 months following the completion of a rehabilitation program.

Cronbach's alpha (Internal Consistency) of the WOSI was 0.91 and the intraclass correlation coefficient (ICC) was 0.96 indicating high reliability. The standard error of measurement was 90.2 with the scale 0–2100 and the minimal detectable change was 250 out of 2100 (11.9%). For construct validity, there was a moderate significant correlation between the Arabic WOSI, the DASH and the ASES with r=0.60 and 0.62 respectively. The WOSI was highly responsive with an effect size of 3.17 and a standardized response mean of 2.94.

The Arabic version of the WOSI is a valid, reliable and responsive tool that can be used to assess patients with shoulder instability.

I, Validity and reliability study.