Subedi M.Sinsurin K.Suttiwong J.Warathanagasame P.Gao Y.Mahidol University2025-08-152025-08-152025-09-01Physical Therapy in Sport Vol.75 (2025) , 98-1041466853Xhttps://repository.li.mahidol.ac.th/handle/123456789/111656Objectives: To develop the Landing Error Scoring System–Modified (LESS–M) and assess its content and concurrent validity. Design: Content and concurrent validity study. Setting: Online expert survey and laboratory-based testing. Participants: Five field experts and 29 healthy individuals. Main outcome measures: Content Validity Index (CVI) and Spearman's rank correlation between LESS–M scores and standard 3D motion analysis. Results: All experts endorsed the lateral single-leg jump-landing task and the modified assessment tool. The ave-CVI and I-CVI were 0.97 and 0.8–1.0, respectively. Moderate correlations were found between the LESS–M score and both knee valgus (ρ = 0.425; p = 0.001) and hip adduction moment (ρ = 0.446; p = 0.001) at peak vertical ground reaction force (vGRF). Conclusions: The LESS–M demonstrated strong content validity based on expert consensus and showed moderate concurrent validity with 3D motion capture for assessing lateral single-leg jump landing. It may be a potential tool for identifying individuals at risk for non-contact ACL injury. Nonetheless, further investigation is required to determine an appropriate cutoff score and to assess the reliability of the LESS–M for broader application.MedicineHealth ProfessionsArticleSCOPUS10.1016/j.ptsp.2025.08.0032-s2.0-10501259861918731600