What is the True Nature of the Trigger Point?

by Dr. Larry Rosen

Much has been written, theorized, and documented concerning the phenomenon known as the Trigger Point. For those of us that treat and study myofascial pain, regardless of our exact specialty, The Trigger Point Manual by Travell and Simons, is the pre-eminent treatise on the subject.

While many accept the validity of trigger point theory as a reality, others are more skeptical, (eg. Quintner Et.al. “ A critical evaluation of the trigger point phenomenon.”) denying its validity entirely. Setting such scientific debate aside for the moment, here I will pose a question: essentially, what in fact is a trigger point? Basically, I believe it comes down to one basic point.

Is the trigger point by nature an area of tissue injury, or is it something else? Right now you are probably wondering why this question is of importance; please bear with me as I attempt to explain below.

The most prominent characteristic of the trigger point phenomenon is pain. More precisely, referred pain and associated phenomena. Generally, pain (psychosomatic pain aside) is considered to be a sign of tissue injury, i.e. an actual or the potential threat thereof. Pain is associated with inflammation, a cardinal sign of tissue injury. Inflammation is associated with inflammatory mediators, of which there are many. These mediators are also part of the trigger point phenomenon. This is well documented by Travell and Simons.

There are many other characteristics of trigger points outlined in the manual that are consistent with tissue injury. Tersely stated, here are some finding consistent with tissue injury:

1. Myofascial pain from trigger points is referred in specific patterns characteristic of each muscle. The referred pain can be elicited, or increased by digital pressure. 2. Active trigger points cause pain, latent TPs are not painful, but restrict ROM. 3. They are also activated directly by stress overload, work fatigue, trauma, and chilling. 4. Weakness and stiffness of the involved muscle may be present as well. 5.Trigger points may cause autonomic nervous system concomitants, and hyperactivity of the motor units involved.

Although abnormalities of blood chemistry have yet to be established, it is possible that eventual abnormalities will be discovered. Biopsy evidence is as yet unclear, some studies show normal tissue, others demonstrate pathological change.

Trigger points demonstrate a group of taut muscles fibers surrounding the TP. Contractions of these palpable bands produce the path gnomonic local twitch response.

Deep palpation of the trigger point elicits the Jump Sign, causing one to withdraw or cry out.

All in all, the above findings, as well as others to numerous to mention here, strongly support the hypothesis that a trigger point is an area of tissue injury, or lesion.

So, case closed. A trigger point is an area of tissue injury! Well, perhaps not and here’s why.

In their manual Travell and Simons never refer to the trigger point as an area of injury! They refer to it, or define it, using words such as locus, spot, or area, however, to the best of my knowledge, never as an area of tissue injury. Certainly, this avoidance of the term injury was not accidental, on the contrary, it must have been intentional, but why? May I offer up an opinion (you’re going to hear it anyway).

Consider one basic but fundamental characteristic of trigger points. They all demonstrate predictable and reproducible characteristic referral patterns, each unique to the involved muscle. The characteristic patterns are consistent over time, both within the individual, and across populations. Any clinician or bodyworker treating trigger points knows that eliciting these unique referral patterns is essential for proper diagnosis.

So, why is this fact of paramount importance? Simply stated, because if one is to assert that a trigger point is an areas of tissue injury, he/she would have to believe that all such injuries occur precisely in the same spot, and present identical signs and symptoms every time, and in every individual. Obviously, this would be impossible.

How then does one reconcile these seemingly contradictory points of view? I have a hypothesis. The trigger point phenomenon has probably evolved over a long period of time.

They are known to occur in species other than man, such as the dog. They are extremely common, yet poorly understood. I propose that the trigger point represents a “strategically” localized area within the myofascial system that serves as an early warning system that tissue damage may occur. Pain is after all, a warning signal that something is wrong or dangerous. Dr. Travell was often heard to say that muscles are unique. They learn. They learn to avoid pain by guarding against movements the cause pain. Hence, the trigger point can be a source of great human suffering, but, it may also be an evolutionary defense mechanism preventing more severe consequences. This is important to consider when treating myofacial pain. The therapist must not only diagnose and treat trigger points, but as Janet Travell would tell you, discover the cause and perpetuating factors underlying the condition.

I welcome your thoughts and observations.