Abstract: Objective To quantitatively evaluate the biomechanical properties and proprioception by comparing the range of motion (ROM), muscle strength, stiffness and proprioception of ankle joint in patients with ankle sprain, in order to provide therapeutic strategy for the patients with ankle sprain. Methods From April to July, 2019, 21 patients with ankle sprain were included. The ROM and muscle strength of bilateral ankle joint were recorded, and the stiffness was evaluated by ankle joint training assistant system, at the end of dorsiflexion and plantarflexion, and plantarflexion 20°. The proprioception of ankle was quantitatively evaluated, including motion perception threshold (MPT) and passive position sense (PAPS). The ROM, muscle strength, joint stiffness, MPT and PAPS were compared, and the correlation among ROM, joint stiffness and proprioception were analyzed. Results Compared with the unaffected side, the dorsiflexion and plantarflexion ROM decreased (|t| > 2.817, P < 0.05), the dorsiflexion and plantarflexion muscle strength decreased (|t| > 5.785, P < 0.01), the stiffness at the end of plantarflexion increased (t = 3.036, P = 0.007) in the affected side. However, there was no significant difference in stiffness at the end of dorsiflexion and dorsiflexion 20° between two sides (t < 0.874, P > 0.05), nor in MPT and PAPS (t < 0.695, P > 0.05). The plantarflexion ROM on the affected side was negatively correlated with the stiffness at the end of plantarflexion (r = -0.466, P < 0.05) and MPT (r = -0.613, P < 0.05), and MPT was positively correlated with the stiffness at the end of plantarflexion (r = 0.469, P < 0.05). Conclusion The dorsiflexion and plantarflexion ROM and muscle strength decreased in the patients with ankle sprain, while the stiffness at the end of plantarflexion increased, which was related to proprioception. Quantitative measurements of ankle joint biomechanics and proprioception contributed to making ankle rehabilitation strategies. Rehabilitation after ankle sprain included training for ROM and muscle strength, and plantarflexion stretch to improve the plantarflexion stiffness, which may promote the recovery of proprioception and ankle function.

Key words: ankle sprain, plantarflexion, range of motion, stiffness, proprioception