Mild symptoms that generally do not interfere with daily activities. Tremor and other movement symptoms occur on one side of the body only. Changes in posture, walking, and facial expressions occur. Symptoms start getting worse. Tremor, rigidity, and other movement symptoms affect both sides of the body or the midline (such as the neck and the trunk). Walking problems and poor posture may be apparent. The person is able to live alone, but daily tasks are more difficult and lengthier. 

Participants are placed based on their individual evaluation. 
 

Loss of balance (such as unsteadiness as the person turns or when he/she is pushed from standing). Falls are more common. Motor symptoms continue to worsen. Restricted in his/her daily activities now, but is still physically capable of leading an independent life. Need to ambulate with a cane/walker for safety. Stiffness in the legs may make it impossible to stand or walk. 

Participants are placed based on their individual evaluation.