Systems and methods are provided for treating chronic pain occurring secondarily to subacromial impingement syndrome in a human body. A system is provided to deliver percutaneous electrical stimulation through at least one electrode to neurological motor points of the posterior and middle deltoid muscles to mediate such pain. One-time, continued and/or periodic dosing of treatment methods according to the present invention may result in a change to central nervous system maladaptive neuroplasticity.