The shoulder, arm, wrist and hand function as what is known as a “kinematic chain.”
Think of this as an anatomical “connected movement” chain. Functioning of each part is connected to, symbiotic with, and consequential with, the other parts.
In-other-words, what's happening at the shoulder may reverberate down and affect the elbow, wrist, and hand. Or in the reverse, dysfunction or injury at the hand, wrist, or elbow can affect the functioning of the shoulder.
This is why, as an Activator Chiropractor, my precise adjustments to correct a problem anywhere in the upper extremity often include adjustments all the way up or down the arm to include all the component parts.