Development of a new scale for evaluating shoulder problems, validity and reliability study

Shoulder dysfunction is a prevalent source of pain and disability worldwide. Although several internationally recognized patient-reported outcome measures exist for shoulder assessment, none have been specifically developed or validated for the Turkish population. Addressing the gap in cultural and clinical applicability, this study aimed to develop a valid and reliable shoulder assessment tool tailored for individuals living in Türkiye. A multi-phase psychometric methodology was employed. An initial pool of 34 items was generated through literature review, patient feedback, and expert input. Content validity was ensured via expert panel review, and item clarity was refined through pilot testing. The preliminary 20-item scale was administered to a sample of 415 patients with shoulder disorders. Exploratory and confirmatory factor analyses supported a three-factor structure comprising joint mobility, functionality, and pain. Following item reduction, the scale was finalized with 12 items. Confirmatory factor analysis demonstrated an acceptable-to-good model fit (χ²(51) = 96.898, RMSEA = 0.048, SRMR = 0.048, CFI = 0.967). The scale showed high internal consistency (Cronbach's alpha = 0.87) and excellent test-retest reliability (ICC = 0.913), indicating temporal stability. Convergent validity was supported by a significant positive correlation with the Shoulder Pain and Disability Index (r = 0.790, p < 0.001). Moreover, multiple linear regression confirmed the scale's strong concurrent validity (Adjusted R² = 0.95, B = 1.97, p < 0.001). In conclusion, the study presents a concise, user-friendly, and psychometrically robust shoulder assessment scale that is both culturally and clinically appropriate for the Turkish-speaking population. It is suitable for use in clinical and research settings, covering multidimensional components such as joint mobility, functionality, and pain. The Shoulder Problems Assessment Scale, the first shoulder assessment tool developed and validated for Turkish speakers, makes an important contribution to the literature.