Gait patterns of asymmetric ankle osteoarthritis patients.

Background: In early stages, ankle osteoarthritis is often asymmetric with only partially degenerated joint surfaces. There is only limited knowledge on the effect of asymmetric ankle osteoarthritis on the patients' gait patterns. Therefore, the aim of this study was to characterize kinematic and kinetic changes compared to healthy adults.

Methods: Instrumented gait analysis was performed in eight asymmetric ankle osteoarthritis patients and 15 healthy controls. Beside conventional gait analysis methods, principal component analysis was used to analyze temporal progression of the most important variables: hindfoot dorsiflexion angle and vertical ground reaction force.

Findings: Asymmetric ankle osteoarthritis patients had a lower hindfoot dorsiflexion and rotation range of motion as well as reduced peak ground reaction forces and peak kinetic values. Principal component analysis revealed that for both the hindfoot dorsiflexion angle and the vertical ground reaction force those principal component vectors affecting the amplitudes had significantly lower principal component scores in patients than in controls. The use of the principal component scores for classification with a linear support vector machine resulted in a high recognition rate of 97.8% for the discrimination between the affected leg and the healthy controls.

Interpretation: Patients with asymmetric ankle osteoarthritis suffer from substantial pathological kinematic and kinetic gait changes. Principal component analysis combined with a linear support vector machine could successfully be used to temporally quantify and classify asymmetric ankle osteoarthritis gait patterns. This study therefore helps to understand the pathomechanism of early stage ankle osteoarthritis from a biomechanical view.