Yet, little is known about the direction of abnormal coupling in conjunction with its degree between joints—muscles—of interest. In this study, we address the directionality of pathological neural couplings between joints, and variability in the degree of them, in the  upper  extremity  post  stroke.  To  evaluate  the  direction  of interjoint  coupling,  joint  motion  and  muscle  activity  in  an involuntary mode while another joint—muscle—was voluntarily activated were assessed in comparison to those made in a volitional mode, focusing on the shoulder, elbow and wrist joints. Overall, involuntary activation of the wrist flexor in the stroke group is observed  when  muscles  of  a  more  proximal  joint  voluntarily activate (p < 0.1 and p <0.05), while activation of the wrist flexor does not lead to involuntary activation of the shoulder muscles and elbow flexor, in comparison to the healthy group. In particular, in the  stroke  group  who  is  assumed  to  have  a  severe  loss  of  the corticospinal system, the wrist extensor is subordinately activated by those about the other joints voluntarily activated (p < 0.05) while it does not cause activations of those about the other joints. These findings indicate that stroke-caused synergies could be directional.