Neurophysiology of Ankle Instability

Chronic ankle instability (CAI) is a common debilitating orthopedic condition that disrupts physical function and decreases quality of life. CAI is heterogenous and can manifest as mechanical ligamentous laxity, perceived disability often referred to as functional instability, or a combination of the two. However, clinicians and researchers most often combine all chronic ankle instability patients without considering these sub-groups, which may account for the poor recovery and recurrent nature of this pathology. Neurocognitive and neurophysiologic discrepancies may explain the different sub-groups; however, technological limitations have previously limited this assessment. The objective of this research is to determine functional and neurophysiological differences between sub-groups of CAI to allow for development of evidence-based rehabilitation which may improve patient outcomes.

To accomplish this, the study will determine the differences among CAI sub-groups on performance of a traditional side-hop test and neurocognitive hop test, determine differences in neurophysiological response and motor control between CAI sub-groups during a lower limb and an ankle specific task, and determine the underlying neurophysiological effects of a 4-week neurocognitively enhanced balance training protocol among CAI subgroups. This study hypothesizes functional performance will be similar between sub-groups during a traditional side-hop test, but those with functional instability without mechanical laxity will perform worse during a choice-reaction hop test compared to those with mechanical ankle instability. It also hypothesizes individuals with functional ankle instability will demonstrate greater cortical activation during the research tasks and after a 4-week balance training protocol compared to individuals with mechanical ankle instability. Time to complete each of the hop tests, cortical activation during the balance and force control tasks, and neurocognitive performance will be assessed to determine differences in performance and neurological function among subgroups of CAI.

Inclusion criteria

• All participants must be physically active (participation in at least 90 total minutes of activity/week including running, walking, lifting weights, or playing a sport, etc.)
• Healthy controls:

• no history of lateral ankle sprain
• no complaints of their ankle giving way
• a Cumberland Ankle Instability Tool (CAIT) score greater than 28
• Coper participants (participants coping with ankle problems:

• a history of lateral ankle sprain, but no episodes of giving way in previous 12 months
• CAIT score greater than 28
• Chronic ankle instability (CAI):

• history of ankle sprain
• two or more episodes of ankle giving way in previous 12 months
• CAIT score less than 25

Exclusion criteria

• History of lower extremity surgery or fracture
• Current signs or symptoms of a joint sprain in the lower extremity
• Pregnancy
• Diagnosis of a vestibular disorder
• Diagnosis of a nerve or connective tissue disorder
• Significant history of condition that impaired cognitive function such as concussion or learning disability
• Currently taking medications that may affect cognitive function such as narcotics, anti-depressants, anti-anxiety agents, or stimulants