There is a condition called myofascial pain which is caused by trigger points.
Trigger points are small areas in a muscle which when pressed cause pain in
other parts of the body. When they are active the referred pain is there all
the time and gets worse when the trigger point is pressed. Trigger points can
cause shortening of the muscle they are found in. They are often overlooked
in the diagnosis of many pain conditions and are mis-diagnosed as other pain
conditions.