Comparison between ankle proprioception measurements and postural sway test for evaluating ankle instability in subjects with functional ankle instability

BACKGROUND: It is important to establish the effective evaluation approaches that are appropriate for measuring ankle proprioception. But, only a few studies used more than one test procedure simultaneously to identify proprioceptive deficits. Further, no data are available on the correlations betw een the measures of ankle proprioception and postural sway (PS) test in subjects with functional ankle instability (FAI). OBJECTIVE: The aim of this study was to identify the relationship between ankle proprioception measurements and PS test in subjects with FAI. METHODS: Of the 79 subjects enrolled in the case-control study, 40 had FAI and 39 were control subjects. Ankle proprioception was evaluated by the angle reproduction (AR), force matching (FM), and the muscle reaction (MR) to sudden ankle inversion tests. For the AR and FM tests, absolute errors (AE) of ankle plantarflexion, dorsiflexion, inversion, and eversion directions were calculated. For the MR test, reaction times and activation of tibialis anterior (TA), peroneus longus (PL), and peroneus brevis (PB) muscles were measured during sudden ankle inversion with a 30° tilting angle. The PS test was investigated by using a force platform during single-limb standing test. Three trials were performed and averaged in each test. RESULTS: Reaction time of the PL (p = 0.006), a variable of MR test, and plantarflexion (p = 0.001, p = 0.009) and eversion (p = 0.016, p = 0.039) error variables of the AR and FM tests differed significantly between the control and FAI groups. Moreover, these variables (r = -0.381 ∼ 0.788, p < 0.05) showed strong significant correlations with the PS test-related variables, among others. CONCLUSIONS: The findings suggest that these variables of ankle proprioception measurements were more sensitive and discriminative than others, and could be useful to assess ankle instability, particularly if the method is to be applied in clinical studies and laboratory settings.