The Effect of Ambient Light on Gait Variability and Joint Biomechanics in Individuals with Unilateral Transfemoral Amputation

Abstract

Background: Visual input is crucial for stable gait, particularly in individuals with transfemoral amputation (TFA) who lack somatosensory feedback from their TFA limb. Low-light conditions may further influence their walking patterns, increasing the risk of falls and joint disorders. Objective: This study examined the effect of ambient lighting on between-limb asymmetry during treadmill gait in individuals with TFA by assessing gait variability and joint biomechanics under regular and low-light conditions. Study Design: Observational study methods: Ten participants with unilateral TFA (six males, age = 36.9 ± 10.4 years, K level ≥ 3) walked at a self-selected speed on a split-belt treadmill under both lighting conditions. Outcomes measures included variability in spatiotemporal variables and sagittal trunk motion, as well as sagittal and frontal plane joint kinetics and kinematics. Two-way repeated-measure analysis of variance was conducted to examine limb asymmetries and limb × light interaction. Bonferroni-corrected post hoc analyses were performed when interaction effects were significant (α = 0.05). Results: Significant between-limb asymmetries were observed in step width variability and sagittal and frontal plane joint biomechanics across both lighting conditions. Under low-light conditions, these asymmetries were reflected by increasing the intact limb step width variability and peak internal hip extension moment, but a decrease in trunk flexion angular velocity variability. Conclusion: These results provide initial evidence that ambient lighting influences gait stability and joint loading in individuals with TFA. Our findings highlight that individuals with TFA are vulnerable to environmental challenges and the importance of considering lighting in designing interventions and fall-prevention strategies. Clinical Relevance: Clinically, attention to environmental lighting may be important when assessing gait, prescribing rehabilitation strategies, and designing fall-prevention interventions for this population. ( J Prosthet Orthot . 2026;X:XX–XX).