Effect of shoes containing nanosilica particles on knee valgus in active females during landing

Objective(s): The effect of silica nanoparticles (SNPs) in sport shoes outsoles on the parameters related to anterior cruciate ligament (ACL) Injury has not been investigated. The aim of this study was to investigate the effect of shoes outsole containing a composite of thermoplastic elastomer based on styrene-butadiene and silica nanoparticles (TPEN shoe) on Knee Valgus Angle (KVA) as a risk factor of ACL injuries during landing Materials and Methods: Fourteen active healthy women without knee injuries and disorders performed bilateral drop jump (DJ) and single leg drop landing (SLL) tasks in barefoot, wearing shoes fabricated with polyvinyl chloride outsole (PVC shoe) and TPEN shoes conditions , randomly. The knee valgus angle values of right and left legs were calculated in the landing conditions. Two factors repeated measures ANOVA were used to investigate the effect of landing and footwear conditions on KVA of right and left legs. Results: For both left and right limbs, the KVA was at maximum and minimum values during landing with barefoot and TPEN shoes, respectively. PVC shoe significantly reduced the knee valgus by 3.84% in left and 4.18% in right knee (P < 0.05) as compared to barefoot landing. In a similar pattern, TPEN shoe significantly reduced the knee valgus compared to barefoot by 7.82% and 9.71% in left and right limbs, respectively. Moreover, the knee valgus during DJ was significantly increased as compared to SLL condition (P < 0.05). Conclusion: Shod landing and specially TPEN shoe decreases KVA compared to barefoot. Our results suggested that using SNPs could produce some viscoelasticity property and a better joint movement control in shoe outsoles which can reduce KVA and consequent reduction of ACL Injury.