Multisegmented ankle-foot kinematics during gait initiation in ankle sprains and chronic ankle instability.

Background: Individuals with lateral ankle sprain and chronic ankle instability have impaired postural control and altered motor strategies during walking. However, little is known regarding foot mechanics during gait. The purpose of this study was to compare three-dimensional multisegmented ankle-foot kinematics during stance phase following gait-initiation in acute lateral ankle sprain (Ankle-sprain), chronic ankle instability (Chronic-instability), Coper, and Control groups.

Methods: 80 recreationally-active individuals (Control: n = 22, Coper: n = 21, Ankle-sprain: n = 17, Chronic-instability: n = 20) participated. Three-dimensional kinematics of the hallux, medial forefoot, lateral forefoot, medial midfoot, lateral midfoot, and rearfoot on shank were collected during the stance phase following gait initiation using an electromagnetic motion capture system. The average joint excursions of 10 steps were normalized to 101 points and analyzed using Statistical Parametric Mapping ANOVA and post hoc t-tests comparing Coper, Ankle-sprain, or Chronic-instability versus Control groups. Secondary analysis was performed comparing Chronic-instability versus Coper groups.

Findings: The Ankle-sprain group had up to 4.1° more rearfoot inversion during midstance (mean difference: 3.1°) from 42 to 49% of stance phase compared to healthy controls. The Chronic-instability group had up to 5.3° more rearfoot inversion (mean difference: 3.6°) from 34% to 91% of stance phase compared to controls. There were no further statistical differences found between Chronic-instability and Copers, other planes, or segments of the ankle-foot complex.

Interpretation: Ankle-sprain and Chronic-instability groups demonstrated more rearfoot inversion compared to controls with no differences in midfoot or forefoot mechanics. Clinicians and researchers should include interventions that control inversion and increase eversion following lateral ankle sprain.