Cultural Adaptation and Turkish Version of the Late-Life Function and Disability Instrument for Individuals with Gonarthrosis: A Validity and Reliability Study

Abstract

Purposes: This study aimed to culturally adapt and assess the psychometric properties of the Turkish version of the Late-Life Function and Disability Instrument (LLFDI) in elderly individuals with knee osteoarthritis (gonarthrosis). Methods: A total of 240 participants aged >= 65 were selected using simple random sampling. The adaptation process followed Beaton's guidelines and included translation, back-translation, and pilot testing. Reliability was assessed using Cronbach's alpha, test-retest, and intraclass correlation coefficients (ICC), while validity was evaluated via exploratory and confirmatory factor analyses and convergent validity with established scales. As part of convergent validity, the relationship of the LLFDI with Barthe Index (BI) and the Functional Independent Measurement (FIM), the Lequesne Index were used. The correlations between the LLFDI scores and these scales were analyzed to determine the level of convergent validity. Results: The LLFDI demonstrated high internal consistency (Cronbach's alpha > 0.70) and test-retest reliability (ICC = 0.734-0.899). Construct validity was supported by Exploratory Factor Analysis (KMO = 0.838-0.952) and significant Bartlett's Test (p < 0.001), revealing appropriate factor structures. Convergent validity was confirmed through significant correlations with the BI, FIM, and Lequesne Index. Conclusion: This study demonstrated that the Turkish version of the LLFDI is a valid and reliable assessment tool for individuals diagnosed with gonarthrosis.