Positioning errors produced by persons with knee joint disease when vision is occluded.

This study examined the effect of occluding static vision on the ability of persons with knee joint disease and impaired position sense to actively reproduce knee angles in a one-legged standing position. The subjects, six women with knee joint disease, ages 54-75 years each performed a series of two knee repositioning tasks in the ranges of 20-40 degrees flexion on two different occasions, both with, and without visual feedback. On each occasion, the leg was marked with reflective markers and the resultant sagittal plane knee angles were photographed. Whilst the absolute differences between the criterion and the matching knee angles calculated from these records showed vision to have an effect on positioning accuracy (p = 0.04), there were no differences in mean absolute constant errors between the two experimental paradigms, indicating similar perceptual judgment in memory. However, variability in performance tended to be greater when vision was occluded (p = 0.08). These findings suggest that while visual sources of information may play a minor role in the knee positioning bias towards target overestimation apparent in this group, supplementary visual cues may help to promote more consistent positioning performance.