1. A method comprising: storing a set of pre-established posture state definitions for delivery of posture state-responsive neurostimulation therapy to a patient, wherein the set of pre-established posture state definitions define one or more existing posture states; receiving a posture state definition update request, from the patient via an external programmer, to update the set of pre-established posture state definitions to include a new posture state in addition to the one or more existing posture states, wherein receiving the posture state definition update request comprises receiving, from the patient via the external programmer when the patient assumes a position, an indication of the position as a boundary of the new posture state; and updating, by at least one processor, the set of pre-established posture state definitions to include the new posture state in response to receiving the posture state definition update request.