Trigger points are areas within muscles tissue that have developed micro-tears as a result of injury. The muscle responds to this injury with a cascade of events.
The first action is for the muscle around the area of injury to contract, producing a tight feeling. When the muscle is in this contracted state, the torn fibers have the opportunity to overlap.
This area of overlapping muscle tissue has muscle fibers that are misaligned and seemingly contorted around one another. It is like a splicing together two ends of a rope by using putty. Adhesions develop within the connective tissue maintaining the torn area with tissue overlap. In time scar tissue will grow over the adhesions.
Within this mass of tissue there is also growth of new nerve tissue and blood vessels. A side-effect of this formation of tissue adhesions and new nerve tissue is the possibility to generate pain!
If these new sensitive nerves are compressed, they can cause pain to be felt (radiated) to other areas of the body. Therefore, “trigger” points can trigger pain in other areas when irritated! For example, an irritated trigger point in the upper shoulder can cause pain to be perceived into the arm.
It has been found that trigger points can form as a reaction to stress, overuse, repetitive motion trauma, bruises, strains, joint dysfunction and surgery. Since the tissues of a trigger point are contracted, and disrupted with scar tissue, oxygen levels become diminished within the trigger point. When muscles cells are deprived of oxygen they switch from the usual efficient aerobic respiration (using oxygen) to the less efficient anaerobic respiration (not using oxygen) for muscle activity.
A byproduct of anaerobic respiration is the formation and accumulation of lactic acid. As every weekend athlete knows, lactic acid build-up leads to increased stiffness and soreness.
So what at first glance may have seemed to be a simple minor muscle injury, has become quite complex. This injury now has associated with it an accumulation of structural, chemical and functional changes.
To further confuse this issue, we also have pain from the injury site and the radiating pain from the trigger points.
It is no wonder that so many people mistake the pain and radiating pain of a trigger point as being due to a more serious tissue injury with nerve damage.
Tender points are completely differently from trigger points. These originate in the condition of fibromyalgia and are found at very specific points on certain tendons. Compression of these tender points causes pain only at the area of compression, there is not any pain referred to other parts of the body.
Because fibromyalgia suffers are so sensitive to touch, the tender points generate a level of pain out of proportion to the actual pressure applied. The Mayo Clinic has defined 18 different tender points that occur with fibromyalgia. To be diagnosed as suffering from fibromyalgia the patient needs 11 out of the 18 tender points.
To further complicate the diagnosis of tender points, most fibromyalgia patients also have a fair number of trigger points. Therefore, a diagnosis should only be attempted by a practitioner familiar with both conditions.