Background <p>To evaluate the validity and reliability of the Turkish version of the General Rehabilitation Adherence Scale (GRAS) in individuals with osteoarthritis receiving physiotherapy.</p> Methods <p>Eighty-eight individuals diagnosed with osteoarthritis and undergoing physiotherapy participated in the study. The scale was translated using a forward-backward translation procedure and assessed for content validity. Construct validity was examined using exploratory factor analysis and confirmatory factor analysis to evaluate model fit. Internal consistency was evaluated using Cronbach’s alpha coefficients. Test-retest reliability was assessed using intraclass correlation coefficients (ICC).</p> Results <p>Content validity indices indicated adequate item relevance. Factor analyses supported a two-factor structure with acceptable model fit indices. Internal consistency was acceptable for the overall scale and subscales. Test-retest reliability demonstrated good to excellent stability over time (ICC &gt; 0.80). The findings indicate that the Turkish GRAS is a psychometrically sound instrument for assessing rehabilitation adherence in individuals with osteoarthritis.</p> Conclusion <p>The Turkish version of the GRAS is a valid and reliable tool for evaluating adherence behaviors in individuals with osteoarthritis receiving physiotherapy. Its use may assist clinicians in identifying patients at risk of poor rehabilitation engagement and may support individualized intervention planning to optimize functional outcomes.</p> Clinical Trials Registry <p>Clin<b>i</b>calTrials.gov Identifier: NCT07107412. Registry date: 30/07/2025. Registry link: <a href="https://clinicaltrials.gov/study/NCT07107412">https://clinicaltrials.gov/study/NCT07107412</a>.</p>