Background: The Lysholm Knee Score (LKS) is a widely utilized patient-reported outcome measure for knee injury patients, due to its robust psychometric properties. It has been translated and validated in several languages, but it has not been translated into Persian.

Purpose: To perform psychometric validation and cultural adaptation for the Persian version of the LKS (P-LKS) in patients with anterior cruciate ligament tears.

Study Design: Cohort study (diagnosis); Level of evidence, 3.

Method: The LKS was translated into Persian using a forward-backward translation procedure. To assess the reliability and validity of the P-LKS, responses were gathered from 100 consecutive patients (mean age, 35 ± 13 years; 91 male and 9 female). These participants also fulfilled the Persian versions of the International Knee Documentation Committee Subjective Form (IKDC-SF) and the 36-Item Short Form Health Survey (SF-36). Construct validity was evaluated by correlating the scores from the P-LKS with those from the Persian IKDC-SF and SF-36. Reliability was determined by examining test-retest reliability and internal consistency. Additionally, floor and ceiling effects, as well as measurement errors, were assessed. The Bland-Altman method was utilized to evaluate absolute agreement.

Results: Construct validity was strong, as >80% of the predetermined hypotheses regarding correlations between the P-LKS and other measures were verified. The P-LKS exhibited a high correlation with the Persian IKDC-SF (r = 0.92) and the physical component of the Persian SF-36 (r = 0.85). Bland-Altman analysis indicated no systematic bias among the test and retest phases. The test-retest reliability and internal consistency for the P-LKS were excellent (ICC = 0.97; Cronbach alpha = 0.88). Floor and ceiling effects for the overall score of the P-LKS were <15% (0% and 2%, respectively). The standard error of measurement was 1.04; the minimal detectable change at the individual level was 2.88, and at the group level, it was 0.29.

Conclusion: The study demonstrated that the P-LKS successfully preserved the attributes of the original version. It can be regarded as a reliable tool for Persian-speaking patients with complete anterior cruciate ligament tear.