Aims: The Landing Error Scoring System (LESS) is a valuable tool for quantifying jump-landing biomechanics and identifying injury risk. While Flexible Flat Foot (FFF) and Genu Varum (GV) are prevalent postural deformities known to influence lower-limb alignment, their combined impact on LESS performance has remained unexplored. This study aimed to compare LESS scores in athletes with concurrent FFF and GV deformities with those of healthy controls. Method and Materials: This clinical trial study recruited 52 male athletes from Tehran sports clubs and allocated them to either a control group (n=26) or a concurrent FFF and GV group (n=26). The deformities were clinically diagnosed by using the navicular drop test (>9mm) and intercondylar distance measurement (>3cm). Participants performed a double-leg jump-landing from a 30-cm box, which was analyzed via video assessment in the frontal and sagittal planes, and their LESS scores were meticulously recorded. Individual LESS items and demographic data were compared using independent t-tests, Chi-square, and Mann-Whitney U tests. The statistical significance level is set at 0.05.
Findings: The groups were demographically similar (p>0.05). The statistical analysis of the total LESS Score (sum of all 17 items) did not reveal a significant difference between the concurrent FFF/GV and Control groups (p>0.05). However, the "joint displacement" did show a significant between-group difference, with the concurrent deformities group having a higher mean rank (U = 237, p = 0.024).
Conclusion: The finding that the total LESS score was preserved suggests that the overall landing strategy may be maintained through compensatory mechanisms. Nevertheless, the significantly greater joint displacement in the deformity group indicates localized biomechanical alteration and a potential compensatory strategy. This highlights that the composite LESS score may mask clinically meaningful impairments. For athletes with FFF and GV, a component-level analysis of the LESS is recommended to identify these subtle deficits and guide targeted neuromuscular and corrective training programs to mitigate injury risk.