Impaired proprioceptive acuity at the proximal interphalangeal joint in patients with the hypermobility syndrome.

Twelve patients with the hypermobility syndrome (> or = 4 on the Beighton score) were examined to establish whether they showed any impairment of proprioception. A position matching paradigm was used which required subjects to align a finger silhouette with the kinaesthetically perceived position of their hidden index finger. Position sense at the PIP joint was found to be significantly (P < 0.0001) impaired in hypermobile patients who made larger matching errors at all angles compared to age- and sex-matched controls. The patients also demonstrated biasing in the direction of errors made when the PIP joint was positioned +/- 20 degrees away from the mid-position. These patients perceived the PIP joint to be less displaced towards the extremes of the range of movement than it really was. The mechanism underlying this impairment of proprioception remains speculative and it is not clear whether this disturbance is a cause or an effect of the hypermobility syndrome.