A shoulder continuous passive motion (“CPM”) device is provided. The shoulder CPM has a motor and a drive mechanism configured to move a slidable arm holder linearly back and forth. The motor can move the drive mechanism linearly back and forth. The drive mechanism can be attached to the arm holder. A user can insert at least a portion of his arm into the arm holder, such that the shoulder CPM device moves his arm linearly back and forth, thereby providing therapeutic treatment to the shoulder of the user.