Plantar Pressure Analysis and the Ankle Instability Index: Quantifying "Giving Away" in Functional Ankle Instability

Area of Science:

• Biomechanics
• Orthopedics
• Sports Medicine

Background:

• Functional ankle instability (FAI) is characterized by abnormal plantar pressure distribution and a subjective
• giving away
• sensation. Objective measures are needed to quantify this instability.

Purpose of the Study:

• To explore the relationship between ankle instability and center of pressure (COP) trajectory deviations during stance.
• To establish the Ankle Instability Index (AII) as an objective parameter for quantifying "giving away" and identifying FAI.

Main Methods:

• A total of 243 participants were divided into FAI and Coper groups.
• Plantar pressure analysis measured medial-lateral COP deviation (Ankle Instability Index - AII).
• Independent-sample t-tests, correlation analysis, and discriminant function analysis were performed.

Main Results:

• A significant difference in AII was found between FAI and Coper groups (18.06±4.82 vs 9.13±3.82, P<.001).
• AII strongly correlated with self-reported ankle instability scores (CAIT and IdFAI).
• AII demonstrated high diagnostic accuracy (91.99%) for FAI with an optimal cut-off of 11.4.

Conclusions:

• The Ankle Instability Index (AII) is a reliable parameter for quantifying the severity of ankle instability.
• AII effectively measures the "giving away" sensation and can identify functional ankle instability.