Evaluation of functional ankle instability assessed by an instrumented wobble board

Objectives Ankle sprains often lead to a history of recurrent injuries and functional joint instability. This study evaluated a new method for assessing functional impairment in patients with chronic ankle instability. Design Case-control study for construct validation purpose. Setting The participants were tested during one-leg standing for 20 s on an instrumented wobble board and on a balance platform. Participants Twenty-five young people with previous ankle sprain and an instability score >11 in the “Identification of Functional Ankle Instability questionnaire” and an age-matched control group of 25 healthy individuals. Main outcome measures Wobble board variation of tilt angle measured by two accelerometers placed horizontally in the board. Results The variation in angular tilt of the wobble board in the medio-lateral direction (standard deviation of tilt angle) was higher in the group with perceived ankle instability than in the control group: 1.5 (0.7) versus 1.1 (0.3). ICC for intra-tester reliability: 0.87 and correlation with COP area measures from the stable balance platform: 0.64. Conclusions People with functional ankle instability display poorer postural stability in the medio-lateral direction when challenged on an unstable surface. The instrumented wobble board may serve as a relevant tool in the clinical evaluation of functional ankle stability.