Chronic anterior talofibular ligament rupture is associated with bilateral knee alterations and reduced ankle plantar flexor moment during gait.

BACKGROUND

With the increasing clinical burden of ankle injuries, particularly anterior talofibular ligament (ATFL) rupture, understanding their biomechanical impact on gait has gained renewed importance. While previous research has established local ankle deficits, the specific proximal compensatory mechanisms-particularly at the knee joint-in patients with MRI-confirmed complete ligamentous discontinuity remain insufficiently characterized.

PURPOSE: The objective of this study was to investigate spatiotemporal and kinetic alterations in ankle and knee biomechanics in individuals with chronic ligament insufficiency during walking compared to normal controls.

METHODS

A total of 78 participants were enrolled in Southwest Hospital. The injury group consisted of 39 individuals with MRI-confirmed complete ATFL rupture scheduled for surgery, recruited from a specialized sports medicine clinic. They were matched with 39 healthy controls. Three-dimensional motion capture synchronized with force plates was used to assess gait parameters, including step/stance times, ground reaction forces, joint angles, and moments.

RESULTS

Patients with ATFL rupture exhibited significantly reduced stride length compared to controls (p < 0.05), whereas cadence, walking speed, step width, and the symmetry indices of step time, stance phase, and swing phase did not differ significantly between groups (all p > 0.05). Sagittal plane kinematic analysis revealed significantly decreased dorsiflexion and plantarflexion excursions at the affected ankle, leading to reduced plantar flexor power generation. Compensatory mechanisms were observed at the knee, where the affected limb demonstrated significantly decreased flexion angles and extension moments.

CONCLUSION

Individuals with chronic ATFL rupture exhibit persistent gait asymmetries and altered lower-limb biomechanics, including reduced stride length, diminished ankle plantar flexor moment, and modified kinematics at both the injured and contralateral knee joints. These findings suggest that functional deficits may extend beyond the ankle to affect proximal joints along the kinetic chain. Although the cross-sectional design precludes causal inference, the observed bilateral kinematic alterations at the knee suggest that proximal joint adaptations may accompany chronic ATFL rupture and warrant further investigation in prospective and interventional studies.