Randomized controlled trial on ankle biomechanics in the treatment of functional ankle instability with joint mobilization

Functional ankle instability (FAI) patients often experience restricted ankle dorsiflexion, increased inversion angle, and elevated ground reaction forces during walking, all related to altered kinematics of the talocrural and subtalar joints. This study aimed to investigate the potential positive impact of joint mobilization on FAI patients from a biomechanical perspective. The experimental group (EG, n = 17; Age: 20.06 ± 1.34 years; Height: 1.74 ± 0.07 m; Weight: 69.79 ± 11.20 kg; BMI:22.88 ± 2.63 kg/m²; CAIT:15.59 ± 2.58; M/F: 15/2) received joint mobilization + routine rehabilitation training, while the control group (CG, n = 16; Age: 20.50 ± 0.73 years; Height: 1.73 ± 0.09 m; Weight: 64.59 ± 7.21 kg; BMI: 21.65 ± 2.47 kg/m²; CAIT: 16.75 ± 2.21; M/F: 14/2) only received regular rehabilitation training. Biomechanical tests were performed in both groups after the 4-week intervention. The spatial parameters during walking (including step length, stride length, step width, step time, cadence, step speed, support time, and swing time), ankle flexion and dorsiflexion angle, inversion, and eversion angles, internal and external rotation angles, ankle torque, as well as the vertical ground reaction force were measured before and after the intervention. The results of the two-way ANOVA showed that the main effect of time was significant for step length (P < 0.001), stride length (P = 0.008), step speed (P < 0.001), the sagittal plane angle at touchdown (P < 0.001), maximum dorsiflexion angle (P = 0.005), sagittal plane toe off-ground angle (P < 0.001), peak flexion-dorsiflexion torque (P = 0.033), the first peak vGRF (P = 0.013), and second peak vGRF (P = 0.011). The main effect of Time * Group was significant for step speed (P = 0.044). The EG demonstrated significant improvements in step speed (P = 0.047), maximum dorsiflexion angle (P = 0.047), and the first peak vGRF (P = 0.028) compared to the CG. This study reveals that joint mobilization intervention enhances gait spatiotemporal parameters, kinematics, and kinetics, particularly in step speed, maximum dorsiflexion angle, and the first vGRF peak for the EG compared to the CG. Therefore, the rehabilitation strategy for patients with functional ankle instability should appropriately increase the use of joint movement to promote the functional recovery of FAI patients.