Intended reaches triggered by exogenous targets often coexist with spontaneous, automated movements that are endogenously activated. It has been posited that Parkinson’s disease (PD) primarily impairs automated movements but it is unknown to what extent this may affect multi-joint-limb control, particularly when patients are off their dopaminergic medications. Here we tested 9 human patients with PD while off-dopaminergic medication vs. 9 age-matched normal controls (NC). Participants performed intentional reaches forward to a target in a dark room and then transitioned back to their initial posture. Upon target-flash, three forms of guidance were used: (1) memory with eyes closed; (2) continuous target vision only and (3) vision of their moving finger only. The trajectories of their arm joints were measured and their joint-velocities decomposed into the (intended) task-relevant and the (spontaneous) task-incidental degrees-of-freedom (DOF). We also measured the balance between these two subsets of DOF as these movements unfolded. In PD patients we found that the incidental DOF were abnormally variable during the retracting movements and prevailed over the task-relevant DOF. By contrast, their forward intentional motions were abnormally dominated by the task-relevant components. Moreover, the patients abruptly transitioned between voluntary and automated modes of joint control, and unlike NC, the type of visual guidance differentially affected their postural trajectories. These findings lend support to an emerging view that there is a loss of automated control in PD which contributes to impairments in voluntary control, and that basal-ganglia-cortical circuits are critical for the maintenance and balance of multi-joint control.