Assessing Functional Ankle Instability with Joint Position Sense, Time to Stabilization, and Electromyography

Context: Functional ankle instability (FAI) is difficult to identify and quantify. Objective: To compare joint position sense (JPS), time to stabilization (TTS), and electromy-ography (EMG) of ankle musculature in recreational athletes with and without FAI. Design: Case-control compared with t tests and ANOVAs. Setting: Sports medicine research laboratory. Participants: 20 recreational athletes. Main Outcome Measures: Passive angle reproduction, TTS, and mean EMG amplitude of the tibialis anterior, peroneals, lateral gastrocnemius, and soleus muscles during single-leg-jump landing. Results: No differences in JPS or medial-lateral TTS measures between groups. Significantly longer anterior-posterior TTS ( P < .05) in the unstable ankle group. The stable ankle group had significantly higher mean EMG soleus amplitude after landing ( P < .05). No other significant differences were found for mean EMG amplitudes before or after landing. Conclusions: Subjects with FAI demonstrated deficits in landing stability and soleus muscle activity during landing that may represent chronic adaptive changes following injury.