## 4 Discussion
[43] showed deficits in ankle proprioception in patients with chronic ankle sprains; and both [PERSON] et al. [10] and [PERSON] et al. [44] noted that insufficient proprioception ability reduced the ability to cope with unexpected perturbations. However, a systematic review by [PERSON] et al. [45] (which didn't include an evaluation of AMEDA assessment) reported no differences in inversion joint position sense in response to perturbation in individuals with recurrent ankle sprains, suggesting that further studies are needed to address the question in individuals with CAI. In the current study, those who were identified with CAI by clinical mechanical assessment showed no reduced ability to cope with perturbations compared with those with no CAI. [PERSON] et al. [25] have previously suggested that CAI is an encompassing term used to classify an individual who presents with both mechanical and functional instability of the ankle joint following an initial lateral ankle sprain injury. In addition, positive correlations were found in the current study between the functional and clinical/mechanical assessments. This result might be attributable to an alternative explanation, whereby a component of CAI is _functional instability_, which may or may not occur in conjunction with _mechanical instability_ or with _recurring sprains_[34]. In other words, these three components can coexist in several combinations [34], with individual sometimes being assessed as having CAI in only one or two of these. When TTT and ADT assessments are positive, they indicate an ankle ligament injury. On the other hand, when these assessment are negative, this does not necessarily rule out CAI [14; 27], Although the clinical assessments in this study correlated with the functional assessments, the ability of the clinical assessment per se to differentiate between those with and without CAI based on their observed responses to unexpected perturbations is limited. The ability of individuals with CAI in the current study to cope with unexpected perturbation was subject to the different standing/walking positions in which the perturbation occurred. To the best of our knowledge, previous studies have not compared individuals' responses to unexpected perturbations when perturbations have occurred in different standing/walking positions. However, previous authors have indicated that the direction, displacement, and velocity of perturbations may influence the kinematic responses and the different postural strategies used [46]. Furthermore, [PERSON] et al. [47] reported different muscle activation patterns in response to different directions/types of unexpected perturbations, and [PERSON] and colleagues [21] suggest that when perturbations were presented on different type of surfaces, different strategies and muscle activations occur in response. In the current study, single-leg perturbations to the lateral (SLOS) or to the medial (SLSS) sides were not correlated with any functional or mechanical instability, nor were differentiations seen between individuals with and without CAI in their responses to perturbations. Similar to our result, [PERSON] et al. [48] described a reduced ability to adjust to a unilateral perturbation in individuals with functional ankle instability--possibly due to a fear of falling even when standing on both legs. It might be suggested that the lack of correlation between SLOS and SLSS positions with any functional or mechanical instability may be due to a ceiling effect--the two single leg tests were too difficult to achieve high scores for perturbation survival, regardless of yes/no CAI. Finally, the tandem position was found to be the main standing posture that differentiated between those with 'unstable' ankes (i.e., individuals who exhibited CAI in at least four of the five mechanical and functional assessments) and those with'stable' ankes (i.e., individuals who exhibited no CAI in at least four of the five mechanical and functional assessments) when responding to perturbations.