Even in the absence of impaired joint laxity, chronically unstable ankles demonstrate a reduced ability to detect afferent signals in response to applied loads, according to research from the University of Delaware.
In 19 healthy ankles and 10 ankles with chronic instability, investigators used microneurography to directly measure afferent traffic from muscle spindles as anterior translation and inversion rotation loads were applied to each joint.
They found no difference in anterior-posterior or inversion-eversion laxity between the two groups at any level of applied force. However, afferent traffic in unstable ankles was significantly diminished at 30 N of anterior-posterior force, a relatively low level.
The results underscore the complex nature of chronic ankle instability and support the concept of neuromuscular training to increase muscle spindle activity in patients with CAI, according to Alan Needle, a graduate student in athletic training at the university, who presented the findings in June at the NATA meeting.
“There’s more to this paradigm of ankle instability than sprain leads to laxity,” Needle said. “Functional instability may exist independent from mechanical instability.”