Tehran University of Medical Sciences Journal of Modern Rehabilitation 2538-385X 0 - 2026 09 12 1472 1472 EN Jalal Ahadi Department of physiotherapy, Faculty of Rehabilitation Sciences, Tabriz University of Medical Sciences, Tabriz, Iran Hakimeh Adigozali Department of physiotherapy, Faculty of Rehabilitation Sciences, Tabriz University of Medical Sciences, Tabriz, Iran Bahram Amirshakeri Health and Environment Research Center, Tabriz University of Medical Sciences, Tabriz, Iran Parvin Sarbakhsh Health and Environment Research Center, Tabriz University of Medical Sciences, Tabriz, Iran Sargol Pirinejad Department of physiotherapy, Faculty of Rehabilitation Sciences, Tabriz University of Medical Sciences, Tabriz, Iran Fatemeh Fekar Gharamaleki 3. Department of Speech Therapy, Faculty of Rehabilitation Sciences, Tabriz University of Medical Sciences, Tabriz, Iran 2025 11 21 2026 05 20 Background: Valid and culturally adapted patient-reported tools are essential for accurate clinical assessment of knee injury outcomes. This study aimed to translate the English Lysholm Knee Scoring Scale (LKSS) into Persian and comprehensively validate it. Methods: This methodological study (test development) employed a cross-sectional design. The LKSS was translated using Guillemin's standard method. Validity and reliability were assessed in a sample of 182 patients with knee injuries. We evaluated content validity (Content Validity Ratio (CVR) and Content Validity Index (CVI)), face validity (impact score), convergent validity (correlation with the International Knee Documentation Committee (IKDC) form), construct validity (Exploratory Factor Analysis (EFA)), and reliability, including internal consistency (Cronbach's alpha), test-retest reliability (Intraclass Correlation Coefficient (ICC)), and Standard Error of Measurement (SEM). Results: All items demonstrated acceptable content validity (CVR >0.79 and CVI >0.62). All face validity impact scores were above the 1.5 threshold. Convergent validity was excellent, with a very high correlation between the LKSS and IKDC (r=0.804, p<0.001). The EFA supported a one-factor structure (KMO=0.829; Bartlett's test p<0.001), explaining 42.39% of the variance. Reliability was outstanding, with an ICC of 0.95, a Cronbach's alpha of 0.894, and an SEM of 5.14. Conclusion: The Persian LKSS demonstrated high validity and reliability across all measured metrics. These results confirm it is a psychometrically sound and suitable instrument for assessing knee-related function and outcomes in the Iranian population, suitable for both clinical and research applications. https://jmr.tums.ac.ir/index.php/jmr/article/view/1472