RESUMO
BACKGROUND: Arthrokinematics (caudal and posterior movements of the talus) and posterior soft tissues of the ankle during ankle dorsiflexion have not been objectively evaluated in detail. This study aimed to investigate the characteristics of arthrokinematics and posterior soft tissues of the ankle during ankle dorsiflexion using ultrasound. METHODS: Thirteen healthy adults participated in the study. Participants whose passive dorsiflexion range of motion (ROM) of the ankle joint was <35° were classified as the restricted group (n = 6), and participants whose passive ankle dorsiflexion ROM was ≥35° were classified as the control group (n = 7). Passive ankle dorsiflexion was performed to measure the ankle arthrokinematics. Strain elastography was performed to measure the elasticity of the flexor hallucis longus (FHL) and Kager's fat pad (KFP) at each dorsiflexion angle. RESULTS: A significant difference in the posterior movement of the talus at the ankle dorsiflexion of 30° was observed between the two groups (P = 0.04). The elasticity of the restricted group was increased at all angles in both FHL and KFP (P < 0.05). CONCLUSION: This study showed that it is possible to objectively evaluate the direction of ankle arthrokinematics and posterior ankle soft-tissue restrictions using ultrasound.