Skin sensory information from the dorsum of the foot and ankle is necessary for kinesthesia at the ankle joint

Previous research has shown that skin is capable of providing kinesthetic cues at particular joints but we are unsure how these cues are used by the central nervous system. The current study attempted to identify the role of skin on the dorsum of the ankle during a joint matching task. A 30 cm patch of skin was anesthetized and matching accuracy in a passive joint matching task was compared before and after skin anesthetization. Goniometers were used to measure ankle angular displacement. Four target angles were used in the matching task, 7 degrees of dorsiflexion, 7 degrees, 14 degrees and 21 degrees of plantarflexion. We hypothesized that, based on the location of skin anesthetized, only the plantarflexion matching tasks would be affected. Absolute error (accuracy) increased significantly for all angles when the skin was anesthetized. Directional error indicated that overall subjects tended to undershoot the target angles, significantly more so for 21 degrees of plantarflexion when the skin was anesthetized. Following anesthetization, variable error (measure of task difficulty) increased significantly at 7 degrees of dorsiflexion and 21 degrees of plantarflexion. These results indicate that the subjects were less accurate and more variable when skin sensation was reduced suggesting that skin information plays an important role in kinesthesia at the ankle. (C) 2010 Elsevier Ireland Ltd. All rights reserved.