Objective Evaluation of Functional Ankle Instability and Balance Exercise Treatment

Lateral ankle inversion sprains occur frequently in sports that mostly concern young, physically active individuals. It constitutes between 15%-75% of all sports-related injuries, and mainly occurs in high-risk sports like team handball, basketball, soccer, or volleyball. Although the majority of patients recover completely after their first acute injury, disabling symptoms of pain and swelling, feelings of instability, and recurrent sprains continue to affect 15% 60% of people at 12 months after an acute ankle sprain despite treatment. Functional ankle instability (FAI) is a poorly defined entity but commonly used to describe patients who sustain multiple ankle injuries with slight or no external provocation and have a subjective feeling of ankle “giving way”. There have been conflicting results reported in literature regarding the role of suggested etiological factors of FAI including deficit in joint proprioception, strength, and stiffness (laxity). Diagnosis of FAI has been mainly relied on a subjective reporting, so is the assessment of FAI treatments. In spite of controversies regarding FAI factors, balance training has been widely used in sports medicine clinics for patients with FAI. Most of past studies reported its effect for FAI, but strong evidence with definitive result is still missing. Furthermore, the mechanism that explains the effect of balance training on FAI is still unclear. Addressing this question was the purpose of this study. Chapter 2 utilized the sudden ankle inversion test to gain insight in the dynamics of early response of the human body. These experiments were performed to understand whether or not human neuromuscular action can significantly influence a body’s response. Fifteen healthy individuals were evaluated and our results demonstrated that the unloading response recorded during the sudden ankle inversion was primarily dominated by the mechanical events. This study showed that during sudden ankle inversion, earlier response may not be due to human reaction iii and late response should be considered to understand the functional behavior of the unloading reaction. Recently, it was suggested that altered threshold to the unloading reaction may be behind ankle giving way episodes in patients with ankle instability. Therefore, we wanted to duplicate this finding in individuals with FAI during sudden ankle inversion test and examine the effects of a four-week balance training program on unloading reactions in individuals with FAI (Chapter 3). Twenty four recreationally active individuals with unilateral FAI were evaluated for unloading reactions on the involved and uninvolved limbs using a sudden ankle inversion test. In seven out of twenty-four subjects, we observed a drastic reaction (hyper-reactivity) in that they were unable to maintain upright standing position when a combination of dynamic ankle stretching and nociceptive stimuli was applied on their affected ankles. The subjects were then randomized to either a control or intervention group. Subjects in the intervention group were trained on the affected limb with static and dynamic components using a Biodex balance stability system for 4-weeks. The control group received no intervention. Only the subjects in the intervention group demonstrated reduced ground reaction forces during the involved ‘with stim’ condition when compared to the control group. This result suggested that balance training may desensitize the hyper-reactivity to unloading reaction in FAI subjects, suggesting a possible mechanism for reducing the ankle “giving way” episodes. The next logical step to better understand the effect of balance training was to investigate on how the balance training affects the subjective self-reported ankle instability. Therefore, Chapter 4 sought to find the effect of balance training on perceived disability in individuals with chronic ankle instability (CAI) and determine predictive factors that can explain CAI or the effect of balance training in individuals with CAI. The results demonstrated that balance training iv can lead to significant improvement in the self-assessed disability. However, the recorded pathological factors demonstrated a limited role in explaining the improvement in self-assessed disability. These results provide evidence that proprioception in ankle inversion, peroneal muscle strength, and inversion/eversion stiffness and neutral zone may not fully explain CAI or the beneficial effects of balance training and additional measures should be assessed for a more comprehensive understanding of balance training in CAI. Other factors, such as impaired proprioception and increased ankle joint laxity, have been shown to be present in individuals with ankle instability. Therefore, Chapter 5 and 6 sought to investigate the effect of balance training on ankle joint position sense and mechanical characteristics of the ankle in these individuals. Our results demonstrated that the balance training program utilized in this study significantly reduced the mean replication errors on the involved limb following intervention at both 15° and 30° of ankle inversion. However, balance training was found to be ineffective in altering the mechanical characteristics of the ankle. In summary, this dissertation work provides evidence that balance training is effective in patients with FAI, however a further study with more sample size and additional outcome measures is required to better understand the mechanism of balance training in these individuals. The findings of this work have implications for research/rehabilitation of not only individuals with FAI but also in individuals with functional joint instability, such as functional knee instability which shares many common symptoms with FAI.