Background: The Rotator Cuff Quality of Life Index (RC-QOL) was developed to evaluate quality of life in patients with rotator cuff disease (RCD). This study provides additional validity and responsiveness testing over a 2-year period in accordance with the Consensus-Based Standards for the Selection of Health Measurement Instruments (COSMIN) guidelines. Methods: Sixty-six patients (mean age, 59±10) with RCD were evaluated. Methodology testing included criterion (concurrent) and content validity, and responsiveness. Results: Content validity was confirmed with a Cronbach α of 0.91 (95% CI; range, 0.92-0.95) and an absence of floor and ceiling effects. Criterion (concurrent) validity was confirmed using the Western Ontario Rotator Cuff Index as a reference standard (r=0.85, p<0.001). The effect size of distribution-based methods of determining responsiveness were large (0.99-1.09) compared to mixed- and anchor-based methods (0.47-0.8). All responsiveness calculations met minimum requirements for acceptable thresholds. Conclusion: The RC-QOL is a valid and responsive measure of health-related quality of life in patients with chronic RCD. The results of this study added to the methodologic quality assessment of the RC-QOL, completing 7 of 10 COSMIN criteria.