Hyperreactivity in Unloading Reaction in Patients with Ankle Functional Instability

W. Liu and M. Santos (USA)


Functional ankle instability, unloading reaction, mechanism, factor.


It is common that after severe ankle sprain patients develop functional ankle instability (FAI) defined as the repeated ankle sprains and/or ankle “giving way” episodes. The causes of FAI have been suggested to include joint laxity, impaired balance control, deficit in ankle proprioception, prolonged peroneal reaction time, and muscle weakness, or a combination of them. The purpose of the current study is to test potential hyperreactivity in unloading reaction in patients with FAI which may explain the mechanism of ankle “giving way” phenomenon. A total of 21 subjects with FAI and 18 normal control subjects were tested for their unloading reactions under nociceptive electrical stimulation when standing with an ankle at supinated position. Other above mentioned potential FAI factors were also tested using a dynamometer device. The unloading reaction was significantly greater in subjects with FAI than that in the control subjects. Such hyperreactivity showed no significant correlation with any of other potential FAI factors. In comparison to other FAI factors, the hyperreactivity showed the highest occurrence frequency. This is a further confirmation that the hyperreactivity in unloading reaction in patients with FAI is an important and independent factor of FAI.

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