Proprioception during manual aiming in individuals with shoulder instability and controls.

Recurrent glenohumeral joint instability is a common orthopaedic problem. One possible cause of this repeated instability is a lack of neuromuscular control and kinaesthetic sense of the glenohumeral joint. The purpose of this study was to determine whether there is a deficit in joint proprioception in subjects with recurrent anterior glenohumeral instability as compared with individuals with no previous shoulder pathology. Subjects were asked to generate pointing movements with their uninjured limb and to match this limb position with the injured limb. Movements of the pointing limb were measured with an optoelectric three-dimensional movement analysis system. These movements were performed in three conditions: 1) with full vision, 2) without vision, and 3) without vision with vibration to the posterior deltoid muscle. For the temporal and spatial measures, there were no significant differences between the control and shoulder instability groups. However, the kinematic data describing arm trajectory formation showed a performance decrement in the no vision with vibration condition for the subjects in the shoulder instability group, suggesting that they suffer from a proprioceptive deficit.