Force sense deficits in functionally unstable ankles.

The purpose of this study was to determine whether participants with functional ankle instability have deficits in force sense reproduction compared to uninjured participants. Twenty participants with no history of injury and 20 with functional ankle instability volunteered for this investigation. Participants in the instability group had a history of at least one ankle sprain and frequent episodes of giving way. Ankle force sense testing was performed at 10, 20, and 30% of eversion maximal voluntary isometric contraction. Ten trials were performed at each force. Absolute and variable errors were then calculated. We observed significant (p < 0.05) main effects for group for absolute and variable errors. Force sense absolute error was significantly greater in the functionally unstable ankles (3.7 +/- 2.2 N) compared to uninjured ankles (2.8 +/- 1.1 N). Variable error was also significantly greater in the functionally unstable ankles (3.2 +/- 1.8 N) than the uninjured ankles (2.4 +/- 0.8 N). Functional ankle instability is associated with deficits in an individual's ability to accurately reproduce a given force. This deficit may impair an individual's ability to set appropriate muscle force levels to provide stability to the joint. (c) 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.