Myofascial pain syndrome is a chronic pain disorder. In myofascial pain syndrome, pressure on sensitive points in your muscles (trigger points) causes pain in seemingly unrelated parts of your body. This is called referred pain.
Myofascial pain syndrome typically occurs after a muscle has been contracted repetitively. This can be caused by repetitive motions used in jobs or hobbies or by stress-related muscle tension.
You can find out more at Mayo Clinic http://www.mayoclinic.org/diseases-conditions/myofascial-pain-syndrome/basics/definition/con-20033195