Trigger Points: Dead or Alive?

Believe it or not, some clinicians, bloggers, medical specialists and others don’t believe in Trigger Points. Some of them even say that they’ve never felt a muscle knot in their life!

Are they right? Is there another explanation why your patients feel pain when they rub their neck or you find just the right spot that reproduces their familiar pain?

In this article I’m going to present both sides of the argument and help you arrive at an informed opinion.

As you start reading this article you might be in one of three camps, the trigger point (TrP) is alive, the trigger point is dead or you’re in the, I’m not sure camp.

By the time you reach the end of the article you might have switched or stayed put, but at the very least you might become better informed and perhaps more engaged in this topical debate, understanding both sides of the argument.

If you’re in the “alive” camp you’re probably wondering why there’s even a reason for a discussion at all. You might be a practitioner whose clinical practice is underpinned by the belief in, and the treatment of, the myofascial trigger point. You regularly diagnose and use your manual therapy skills to treat patients who present with myofascial pain syndrome.

Those of you who are in the “dead” camp might hold equally fervent beliefs about the demise of the trigger point as well as the relationship between trigger points and myofascial pain. You might also feel that this mythical clinical phenomenon is not only “dead”, but well and truly buried.

Then there’s the rest, who are in neither camp at this point, and are willing to listen to both sides of the argument in order to make a decision, one way or the other.

Let’s start with the arguments against the existence of the myofascial trigger point. There are several blog page and journal article contributors who express their belief that trigger points do not exist and furthermore, have no scientific basis (1)

The arguments against the existence of the trigger point relate to the following points:

• There’s virtually no inter-examiner reliability for either putative trigger points or taut bands. Physical examination of trigger points, in other words, palpation cannot be relied upon from a diagnostic perspective, even among expert examiners. (2)

• The reported alterations in the biochemical milieu in and around tissue that is identified as a trigger point, using palpation, are not unique to that tissue, and can be found in non-affected tissues. (3,4)

• End plate noise, which is thought to be a trigger point characteristic, is not restricted to trigger points alone, and therefore its existence cannot be used as a reliable diagnostic criterion. (5,6)

• Results from studies attempting to visualise and distinguish between active and latent trigger points using diagnostic ultrasound, sonoelastography, Doppler imaging, and magnetic resonance elastography are confounded due to lack of pain free controls in the studies, as well as results that show an inability to distinguish between normal and trigger point tissue. (7,8,9,10,11)

• Biopsies of animal muscle tissue used to correlate palpable taut bands with histological and morphological changes did not show any correlation. (12)

• Palpation of eccentrically loaded muscle tissue and subsequent detection of taut bands is not a reliable methodology for identifying trigger points. (13)

The trigger points are dead camp don’t believe that trigger points can be palpated, they cannot be detected by ultrasonography techniques, they don’t cause any unique biochemical or electromyography changes, they don’t have any unique histological appearance that could distinguish them from local unaffected tissues, and finally exercise does not cause the formation of trigger points.

At first glance, it appears that there are many arguments supporting the demise of the trigger point. However, on closer inspection, as is usual with most arguments, there are really only two main arguments: they can’t be reliably palpated and nothing changes within the body to indicate their existence.

Now to the trigger point is alive and well camp.

One of the ways to present this side of the argument is to delve deeper into the research that is used to support the “dead” camp.

One can be forgiven for being a little confused by the naysayers when they make statements like “Therefore, the theory of Myofascial Pain Syndrome (MPS) caused by TrPs has been refuted. This is not to deny the existence of the clinical phenomenon themselves, for which scientifically sound and logically plausible explanations based on known neurophysiological phenomena can be advanced.” (1)

So, is the “dead” camp saying that TrPs exist but we’re not sure how they get there or are they saying that they don’t exist at all?

Manual therapists have long relied upon palpation to determine areas of soft tissue tension, resistance, and changes in tensional balance between fascial layers. (14)

 

Practitioners who use their hands to detect and treat these soft tissue changes, owe their very existence to mastering this skill. Asking an experienced manual therapist to find a trigger point, anywhere in the body, whether the patient complains of pain or not, would probably be seen as an insult not a challenge. It’s what they do, day in, day out.

No doubt this statement will invoke criticism from the self-proclaimed “scientific” and logical thinkers that I have fallen victim to the perils of circular reasoning. I can of course understand the criticism but I do not agree with it.

Let’s look at the research into interrater reliability, more closely, and the reasons why some trigger point skeptics say that the research shows poor or no reliability.

There are in fact numerous Inter-examiner or Inter-rater reliability studies (15-25) , which conclude that reliability is certainly possible in many different parts of the body including the upper trapezius, the periscapular region and the lower leg.

Here are some examples…

1. This study has demonstrated that it is possible to demonstrate the presence of the taut band, spot tenderness, jump sign and pain recognition reliably between sessions using the same examiner. (18)

2. The results of this study support the idea that experienced raters can obtain acceptable agreement when diagnosing MTrPs by palpation in the three shoulder muscles studied. Allowing for patient report of pain recognition may provide for even better interrater reliability results. (15)

3. This study provides preliminary evidence that MTrP palpation is a reliable and, therefore, potentially useful diagnostic tool in the diagnosis of myofascial pain in patients with non-traumatic shoulder pain. (15)

4. The findings of this study suggest that an experienced physiotherapist using the MTrP palpation protocol can reliably locate a Myofascial Trigger Point (MTrP) in the upper trapezius muscle. (19)
5.

6. Among non-expert physicians, physiatric or chiropractic, trigger point palpation is not reliable for identifying taut bands and local twitch responses. (20)
7. Interrater reliability between two examiners identifying MPS subjects with MTrPs in upper quarter muscles exhibited substantial agreement. These results suggest that clinical criteria can be valid and reliable in the diagnosis of MPS. (21)

8. The results have shown an acceptable evidence of reproducibility on classification and location of MTrPs in the epicondyle musculature among expert practitioners, while the reliability was significantly lower when comparing with an inexperienced evaluator. (22)

9. Inter- and intra-tester reliability of active and latent MTrP evaluation was moderate to substantial. Palpation evaluation can be used for clinical diagnosis of MTrP’s in the hip and thigh muscles. (23)

10. This study provides evidence that intra and inter examiner reliability is acceptable for clinical practice to identify MTPs in the shoulder muscles of subjects symptomatic and asymptomatic for SIS; however, the symptomatic side demonstrated lower reliability in inter examiner assessment. (24)

11. Three blinded raters were able to reach an acceptable pairwise interrater agreement (PA value≥70%) with regard to the presence or absence of MTrPs and LTR in the Tibialis Anterior muscle and in the nodules in taut bands; referred pain; and the jump sign in the Extensor Digitorum Longus. (25)

These conclusions will not come as surprise to those of you who have observed the all too common laggard nature of manual therapy related research, which is often way behind what we’ve known and would expect. Rather than science revealing something new and adding to our knowledge it merely confirms what is already known.

It is interesting to note the conclusions that the ”dead” camp draw particularly from research that seeks to test inter-examiner reliability (2), one such conclusion, as mentioned earlier determined that “there was virtually no inter-examiner reliability” (1)

In the interests of fairness the conclusions from this study by Wolfe et al. should be scrutinised more closely.

In this study, four experts on myofascial pain syndrome (MFP) performed trigger point examinations and 4 experts on fibromyalgia performed tender point examinations on 3 groups of subjects (7 patients with fibromyalgia, 8 with MFP, and 8 healthy persons) while blinded as to diagnosis.

The results actually show positive conclusions about inter-examiner reliability:

• Local tenderness was common in both disease groups (65-82%), but was elicited in a greater proportion of MFP experts’ examinations (82%).

It should be said that there were problems with this study with respect to definitions and design, which the authors clearly cite. It is also a very small study and we should be cautious about drawing any firm conclusions.

Given the overwhelming positive conclusions that the studies listed above present (15, 18-25), one has to wonder why others find it difficult to accept that experts or raters in these studies can reliably palpate trigger points.

Perhaps it might be because they have sausage fingers? This unusual and somewhat rare affliction is blamed for the inability to have ever felt a taut band or knot by some in the “dead” camp. (26)

Indeed, it has been suggested that because only expert examiners can reliably locate trigger point locations, this detracts from the results of these studies and therefore trigger points don’t exist. This position doesn’t make sense.

Firstly, we would expect that the more experience a rater has in a given skill, the better they will be at performing that skill, there’s nothing surprising about this.

Secondly, it’s doesn’t follow that because experts are more reliable than non experts at locating trigger points we should abandon the possible existence of trigger points.

The other frequently regurgitated argument is that nothing can be seen to change in or around a trigger point.

Well, is that really the case?

Let’s use the paper by Shah et al. (3) as a clear example of cherry picking the results to support ones point of view.

This paper uses a novel in vivo microanalytical technique for measuring the local biochemical milieu of human skeletal muscle. Three subjects were selected from each of three groups (total 9 subjects): normal (no neck pain, no MTrP); latent (no neck pain, MTrP present); active (neck pain, MTrP present). The microdialysis needle was inserted in a standardized location in the upper trapezius muscle.

Concentrations of protons, bradykinin, calcitonin gene-related peptide, substance P, tumor necrosis factor-α, interleukin-1β, serotonin, and norepinephrine were found to be significantly higher in the active group than either of the other two groups (P < 0.01). pH was significantly lower in the active group than the other two groups (P < 0.03).

The term “significantly higher”, to most would mean that something is different about the biochemistry in and around a trigger point versus a non-trigger point region.

Another interesting study (27) goes a step further and concludes that dry needling at Myofascial Trigger Spots (MTrSs) can modulate biochemicals associated with pain, inflammation, and hypoxia depending on the dry needling dosage is supported by our data.

This study investigated the activities of β-endorphin, substance P, TNF-α, COX-2, HIF-1α, iNOS, and VEGF after different dosages of dry needling at the myofascial trigger spots (MTrSs) of a skeletal muscle in rabbit.

In another study (28) the authors presented a new objective, quantitative measure, the mechanical heterogeneity index, which can be used for quantifying soft tissue properties of muscle based on vibration elastography in patients with myofascial trigger points.

Turo et al. were able to able to demonstrate that this measure provides objective and reproducible documentation of the extent of mechanical heterogeneities in the upper trapezius muscle and is sensitive to and correlates with changes in the status of the point as determined by physical examination.

Furthermore, myofascial trigger points in upper trapezius muscles that have lower heterogeneity at baseline were found to be more likely to resolve from active to palpably normal muscle. In their study population, for a baseline mechanical heterogeneity index of less than 0.14, they observed 69% sensitivity and 80% specificity for predicting trigger point resolution after a 3-week course of dry needling.

There are many other important contributions that support the existence of the trigger point and there will be many more.

If this was a court of law, and we were considering whether or not we should banish the trigger point to empirical nonsense, we would have to convince many that the trigger point cannot be reliably and consistently palpated, and that the biochemical, ultrasonography changes many have reported are an aberration.

This article demonstrates that there is not just reasonable doubt about these assertions but a growing tide of research that supports the belief that the trigger point is alive and well.

 

Declaration of Interest

Dr W. Mahmoud, author of this article is Director of CPD Health Courses, which presents Dry Needling Courses for Health Professionals.

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