Effects of ankle joint biomechanics and foot postures on Achilles tendon force during running through a simulation study

Achilles tendinopathy is a prevalent injury observed among runners. Achilles tendon force (ATF) and differences in foot posture are considered factors in the occurrence of Achilles tendinopathy. This study was conducted using computer simulations. The simulation ranges were determined for the ankle joint angle (-25° to + 25°) and plantarflexion moment (0-160 Nm) at variable running speeds using a public dataset. The ankle angle was used to compute the Achilles tendon moment arm. Moment arms specific to the normal foot, pes cavus, and pes planus were calculated using radiographs from a previous study. Finally, the plantarflexion moment was divided into moment arms to obtain the ATF. For all foot postures, the ATF increased as the ankle dorsiflexion angle and plantarflexion moment increased. At most ankle angles, the ATF was found to be higher value in the order of pes cavus, normal foot, and pes planus. Increasing dorsiflexion angles and plantarflexion moments during running may lead to the occurrence or worsening of Achilles tendon tendinopathy. Additionally, individuals with pes cavus are more likely to develop Achilles tendinopathy than those with other foot postures.