Watch this link for explanation on how muscles work and the formation of a trigger point. 

What is a Trigger Point

They are tight bands within the muscles (knots) that cause pain and lack of mobility within  that muscle. In the vast majority of cases the pain is felt in a different area than that particular muscle (referred pain).

There are about four hundred muscles in the human body and any one of them can develop trigger points, potentially causing referred pain and dysfunction. Symptoms can range from intolerable, agonizing pain to painless restriction of movement and distortion of posture.

You may have many Trigger Points, but you may only feel a few. The ones that you feel and give you the painful problems are called Active and those that you feel when you press on them are called Latent. The Trigger Points that most clients come to see me about, are the active points.  These are the ones that create pain and restrict their motion.

Most of the time, Trigger Points are not located in the same place where you feel symptoms. This means that if you only work  on the area where you fell pain, you probably will not get pain relief.  For example, Trigger Points in the upper portion of your back (between the neck and your shoulder) can cause you pain in your temples, at the base of your skull, in the side of your jaw and possibly above your ear and over your eye.

When pressure is applied to a Trigger Point it often reproduces the referred pain pattern this muscle is known for. 

Referred tingling, numbness, or burning sensations are most likely due to Trigger Points contracting around or putting pressure on a nerve.

Trigger Points cause weakness and loss of coordination of the muscle involved, along with this muscle being unable to tolerate being used. Many people, including Sports Trainers, take this as a sign that you need to to strengthen the weaker muscle.  However, if the Trigger Points aren't deactivated first, the conditioning exercises will likely encourage the surrounding muscles to do the work instead of the muscle containing the Trigger Point.  This will cause the weakening of the muscle with the Trigger Point.

The more intense your pain is, the  greater the number of active Trigger Points you're likely to have. 

Pain is very unpleasant, both physically and emotionally,and the more anxious we get about the pain, the worse the pain will seem. For more than any other reason, pain take  us to our doctors or other health professionals, for help and advice. Pain can be mysterious, with no obvious cause, and this is the most worry of all. Our imagination can take hold, and an ache that is the result of nothing more than poor posture can escalate into something very serious in a person's mind. this sort of thinking the worse is even more likely when the pain is felt in an area where there really is nothing wrong. a pain in the face and head might be the result of trigger points in muscles of the neck area but because the pain is in the face, around the ear, or your eyes,it is in these areas that we might imagine that we have a serious problems. Once you know that the pain is actually in your neck or shoulder muscles, it gets rid of your anxiety. 

Watch this short video put together by WebMd. At our clinics we us the palpation method not needling injections

 http://www.webmd.com/video/trigger-point-therapy-pain?ecd=wnl_cbp_092508