Individuals with Functional Ankle Instability have Contralateral Lowload Force Sense Deficits but not Joint Reposition Sense Deficits

Abstract

1331 Proprioceptive deficits following an ankle sprain are reported as a factor leading to functional ankle instability. While force sense has not been extensively investigated at the ankle, there are conflicting results from studies of kinesthetic awareness and joint reposition sense in participants with functional ankle instability. PURPOSE: To establish the relationship of contralateral force sense (FS) and joint reposition sense (JRS), with functional ankle instability. METHODS: Sixty participants (13 with no history of ankle injury, 47 with a history of 1 or more ankle sprain, 22.4 ± 4.9 yrs, 169.9 ± 9.7 cm, 72.6 ± 16.3 kg) were recruited to participate in the study. Contralateral reproduction (i.e. referencing with the ipsilateral limb and reproducing with the contralateral limb) was used for the FS and JRS testing. FS testing was done with a load cell at 10 & 30% of maximal voluntary isometric contraction (MVIC). Participants held the target force for 5 seconds, followed by an immediate reproduction of the force. JRS testing was done with an electric goniometer at 20° of inversion and 10° of eversion from subtalar neutral. Participants held the target angle for 15 seconds, followed immediately by the reproduction of the angle. Three trials were completed for each force and angle. The last second of the reference point and the first second of the reproduction point were subtracted to produce an error score for each trial. Absolute (AE), constant (CE), and variable (VE) errors were calculated from the trials. Correlations were computed with ankle instability and JRS and FS errors. RESULTS: No relationship was revealed between ankle instability and inversion or eversion joint reposition sense, with r values ranging from −.24 to .11. A significant relationship was found with force sense. Specifically, variable error force sense at 10% MVIC was positively correlated to ankle instability (r = .28; df = 59; P< .05). Force sense at 30% MVIC did not produce a significant relationship with values of r ranging from −.01 to .09. CONCLUSION: Deficits of low load force sense, but not joint reposition sense are present in individuals with ankle instability. While these are both measures of proprioception they are testing very specific conscious proprioceptive senses. They each potentially target different receptors, afferent pathways, and control mechanisms. These findings suggest that a significant ankle injury may cause damage to part of the sensorimotor system, without disrupting other components.