The Effects of Chronic Ankle Instability on the Biomechanics of the Uninjured, Contralateral Ankle During Gait.

Objective: To determine whether unilateral chronic ankle instability (CAI) affects the kinematics of the uninjured contralateral ankle.

Methods: In this case-control study, 15 adult patients with unilateral CAI and 15 healthy controls were studied. Both the unstable and uninjured ankles in patients with unilateral CAI (CAI group, n = 15) were compared with that of healthy individuals (control group, n = 15). Applying body photo-reflective markers, the participant's motion during gait was measured. Biomechanical variables including overall ankle-toe angle, linear velocity, linear acceleration, angular velocity, angular acceleration, range of motion (RoM) in dorsiplantar flexion, and inversion-eversion at initial contact, loading response, mid-stance, terminal stance, pre-swing, and swing phase of the gait were measured.

Results: In patients with CAI, the injured and uninjured ankles were significantly different regarding angle-toe angle, inversion-eversion RoM, dorsiplantar flexion in mid-stance, inversion-eversion at initial contact and terminal stance as well as the pre-swing and swing phases (p < 0.01). The uninjured ankles of patients showed lower ankle-toe velocity (p = 0.01) and acceleration (p = 0.01) compared to both the left and right ankles of the controls. In addition, the uninjured ankles of the patients showed decreased ankle dorsiflexion and increased inversion during initial contact, loading response, mid-stance, terminal stance, pre-swing, and swing compared to the control group (p < 0.017).

Conclusion: The results suggest that unilateral CAI can affect gait biomechanics in the contralateral uninjured ankle. Left unaddressed, unilateral CAI may lead to increased morbidity to the contralateral uninjured side. When surgery is not preferred for the management of unilateral CAI, rehabilitation protocols should focus on both sides.