Cross-cultural adaptation, reliability and validity of the Turkish version of the Lower Limb Functional Index

Abstract

Purpose: This study aims to adapt culturally a Turkish version of the Lower Limb Functional Index (LLFI) and to determine its validity, reliability, internal consistency, measurement sensitivity and factor structure in lower limb problems. Method: The LLFI was translated into Turkish and cross-culturally adapted with a double forward–backward protocol that determined face and content validity. Individuals (n = 120) with lower limb musculoskeletal disorders completed the LLFI and Short Form-36 questionnaires and the Timed Up and Go physical test. The psychometric properties were evaluated for the all participants from patient-reported outcome measures made at baseline and repeated at day 3 to determine criterion between scores (Pearson’s r), internal consistency (Cronbachs α) and test–retest reliability (intraclass correlation coefficient – ICC2.1). Error was determined using standard error of the measurement (SEM) and minimal detectable change at the 90% level (MDC90), while factor structure was determined using exploratory factor analysis with maximum likelihood extraction and Varimax rotation. Results: The psychometric characteristics showed strong criterion validity (r = 0.74–0.76), high internal consistency (α = 0.82) and high test–retest reability (ICC2.1 = 0.97). The SEM of 3.2% gave an MDC90 = 5.8%. The factor structure was uni-dimensional. Conclusions: Turkish version of LLFI was found to be valid and reliable for the measurement of lower limb function in a Turkish population.Implications for RehabilitationLower extremity musculoskeletal disorders are common and greatly impact activities among the affected individuals pertaining to daily living, work, leisure and quality of life.Patient-reported outcome (PRO) measures have advantages as they are practical, cost-effective and clinically convenient for use in patient-centered care.The Lower Limb Functional Index is a recently validated PRO measure shown to have strong clinimetric properties.