The correlation between postural control and upper limb position sense in people with chronic ankle instability

This study investigated the sensorimotor function of different body sites in participants with recurrent ankle injuries. As noted in recent systematic reviews [9, 10], postural stability measures in single-leg stance did not discriminate between participants with CAI and those without, as well as between the limb with recurrent sprains versus the unaffected limb in the CAI group. It should be noted, however, that while the measure of static postural stability may not be sensitive enough to detect deficits associated with CAI, more dynamic assessments, such as the single-leg-hop stabilisation maneuver, may have the ability to defer between individuals with CAI and individuals with stable ankles [28, 29]. In addition, reports of postural assessment through the Balance Error Scoring System have also shown promise in detecting differences between those with and without CAI [30].

Similar to lower limb postural stability results, there was no difference in the shoulder position sense between the CAI and control groups. This is consistent with the findings of Hung et al. [31], who found that people with unstable shoulders can perceive active shoulder angles as accurately as those with healthy shoulders.

While the sensorimotor function of the different body sites was similar in both groups, examination of the correlations between the body sites differentiates the groups. In the able-bodied group, Pearson correlations showed significant positive correlations between the same joint on the right and left sides, as well as significant positive correlations between the upper and lower limb in the non-preferred/left side. This may suggests a site-specific and a non-preferred side attribute in the way the brain integrates proprioceptive information. However, in the CAI group there was no correlation between the upper and lower limb and significant positive correlations were found only between the lower limb on the right and left sides.

It has been suggested that joint injury may be more likely to occur when there is a “pre-existing, global deficit” in proprioception [14]. It is not clear whether individuals with CAI have a “pre-existing, global deficit”. However, the lack of correlation demonstrated in the CAI group may suggest difference in the sensorimotor integration and processing post-injury, when compared to healthy participants. Dynamic movements involving multiple body segments, such as locomotion, require controlling and coordinating the arms and legs to accomplish a rhythmic, smooth, movement pattern [32]. Indeed, it has been shown that people with recurrent ankle sprains may have a typical altered gait pattern that might be related to altered control of the central nervous system [33, 34]. Furthermore, in a study that compared the effect of dual tasking on postural performance in participants with CAI and a matched control group, concurrent performance of a cognitive task decreased postural stability only in the participants with CAI [35]. This may also suggest a deficit in central neural control for maintenance of balance in that group. To our knowledge, the present study is the first to describe the lack of correlation in sensorimotor function in a sample of participants with recurrent ankle sprain.

The greatest challenge presented by CAI may not be in treatment, but in prevention [36]. A recently published position statement by The National Athletic Trainers Association, intended to provide recommendations for conservative management and prevention of ankle sprains, indicated that clinicians should implement a multi-intervention injury-prevention program that focuses on balance and neuromuscular control to reduce the risk of ankle injury [37]. Our results suggest that this multivariate approach should include sensorimotor exercises and tasks that coordinate the upper and lower extremities. For example, throwing a ball toward a specific target, while standing in a single limb stance on a wobble board or soft surface. It is also recommended that accurate assessment and documentation of progress of such activities should be a standard part of ankle-rehabilitation programs.

It has been suggested that there is non-preferred limb superiority in the utilisation of proprioceptive feedback. The advantage of the non-preferred limb is attributed to the functional differences between the roles of limbs especially in bilateral tasks. The non-preferred limb usually stabilises a specific position to enable the preferred limb to manipulate and perform a task [16]. For example, while hammering a nail or kicking a ball. Thus, joints in non-preferred limbs are more likely to receive more “positioning” practice, resulting in more accurate discrimination of movement. The results in the control group, which demonstrated correlation between the upper and lower limb only in the non-preferred (left) side may support this ‘superiority’ hypothesis. Nevertheless, as reported by previous studies [25, 38], the study results did not demonstrate differences in the tested performances between the preferred and non-preferred shoulder and ankle. A possible explanation may be related to the joints tested and the evaluation method in the current study. Proprioceptive asymmetry was mainly evident at distal joints and under non-weightbearing conditions [39‐41]. However, the present study included only one distal joint (i.e., the ankle), which was evaluated in a weightbearing condition. Furthermore, the evaluation was of postural control that is affected by proprioception as well as by the motor control system. Therefore, it is not surprising that asymmetry was not reported in the present study. Future studies with multiple joints should be conducted to evaluate whether proprioceptive asymmetry exits.

The present study has several limitations. Firstly, different aspects of sensorimotor function were evaluated in the upper (i.e., position sense) and lower limb (i.e., postural control). When testing sensorimotor function and acuity, it is important that the tests maximise external validity (i.e., the similarity between the laboratory and real life function) [42]. The shoulder test was selected to simulate the abducted, externally rotated position of the shoulder required in many sporting activities and the ankle test was chosen as it has the advantage of testing in the weightbearing position. The similarity of these tests to normal function enhances the external validity of the current study. Nevertheless, future investigations in people with CAI should examine inter-limb correlations using the same aspects of sensorimotor function. Secondly, the study cohort consisted of a relatively small sample, with a narrow age range, and it included only participants who demonstrated right upper and lower limb preference. Thirdly, while the enrolment criteria for the CAI group were based on self-reporting of ‘giving way’ and feelings of ankle joint instability, it did not include the use of an ankle instability questionnaire, such as the identification of functional ankle instability (IdFAI) [43]; By not using the ankle instability questionnaire eliminated our ability to quantify this aspect of perception. Future studies with larger and varied samples that also confirm self-reported ankle instability with a validated ankle instability-specific questionnaire, are warranted.