Outpatient Physical Therapy Intervention in Subjects With Parkinson's Disease Currently Using APOKYN®

Multicenter, outpatient trial to evaluate PT outcomes in subjects diagnosed with PD and currently using APOKYN. Those subjects who satisfy all eligibility criteria will be randomized to 2 treatment groups: 1. "APO+" (APOKYN treatment before the PT Intervention Visit) and; 2. "APO-" (APOKYN treatment withheld before the PT Intervention Visit). The study will have: * Baseline Assessment Visit(s) - 1 day at Investigator's clinic and PT clinic * APOKYN Response Verification Visit - 1 day * PT Intervention Visits - for 6 weeks * End-of-study Assessment Visit(s) - 1 day at Investigator's clinic and PT clinic All subjects will participate in a standardized PT intervention. In both treatment groups, ALL subjects will arrive for the PT Intervention Visit in an "end-of-dose-off" motor state. The "end-of-dose-off" motor state will be achieved by the subject withholding his/her carbidopa/levodopa dose and APOKYN dose for at least 3 hours before the PT Intervention Visit. It is hypothesized that the outcome of PT will be improved when subjects are in the "on" motor state during PT Intervention visits compared with being in the "end-of-dose-off" motor state during PT Intervention visits.