Is a tendency to be unstable when standing upright and it is one of the most important signs of Parkinson’s. A person with postural-instability has lost some of the reflexes needed for maintaining an upright posture. Some people develop retropulsion a dangerous tendency to sway backwards when rising from a chair, standing or turning. Test for postural- instability is call “pull test.” it is moderately forceful backwards tug on the standing individual to see how well the person recover. People with Parkinson’s are unable to recover, and would tumble backwards.