Myofascial Pain Synrome (or MPS) is a term used to describe one of the conditions characterized by chronic pain. It is associated with and caused by "trigger points" (TrPs), sensitive and painful areas between the muscle and fascia. Simons has visibly identified and documented these contraction knots through electromyographic imaging, ultrasound, and biopsy. The symptoms can range from referred pain through myofascial trigger points to specific pains in other areas of the body.