Santos MJ, Liu W
The objective of this case control study was to classify individuals with functional ankle instability (FAI) into deficit and non-deficit categories based on the evaluation of the most common factors that have been proposed to be related to FAI. A combination of factors including ankle proprioceptive deficit, muscular weakness, impaired balance, delayed neuromuscular reaction time, and joint laxity were tested bilaterally in 21 individuals with FAI and in 16 healthy control subjects. The results showed that balance control and evertors' strength were significantly less on the affected side in comparison to the unaffected side in subjects with FAI. The evertors' strength was also significantly different between the side difference of the FAI group and the side difference of the control group. Passive ankle stiffness was significantly correlated to balance control, ankle proprioception, and evertor peak torque. Individuals with FAI demonstrated a large variation in the deficit categories ranging from multiple deficits to no noticeable deficits.
Mechanical alterations in the ankle joint may influence several aspects of the ankle's functional ability. Alterations in the afferent processes, represented in this study by ankle proprioception, may effect the evertors' strength or vice versa. More importantly, individuals with FAI might exhibit high variability in ankle deficits.
Journal of Orthopedic and Sports Physical Therapy, 2008, 38(3), 150-7