Myofascial Trigger Point
Editor: Rhonda K. Kotarinos, DPT, MS
December 2017

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IUGA/ICS definition: “A tender, taut band of muscle that can be painful spontaneously or when stimulated. The taut band is electrically silent.” Foot Note - Local or referred pain may be reproduced. An active TrP is said to have a characteristic “twitch” response when stimulated; however, the twitch response to palpation has been shown to be unreliable. The most reliable sign of a TrP is sensitivity to applied pressure. Trigger points are implicated in myofascial pain; however, the validity of this theory is controversial and has recently been refuted. (1, 2)

Current expert based definition: International Delphi panel of 60 experts from 12 countries (3)
Active trigger points “an active trigger point upon stimulation reproduce any symptom experienced by the patient, either partially or completely, whereby the symptom is recognized as a familiar experience by the patient, even though it may not be present at the moment of the examination.” (3)
Latent trigger points “trigger points that upon stimulation do not reproduce any symptom experienced by a subject (symptomatic or asymptomatic) and the subject does not recognize the elicited symptom as familiar.” (3)
Diagnostic criteria include at least two of the established criteria be present to diagnose a trigger point: a taut band, a hypersensitive spot, and referred pain. (3)

The following two statements that are considered definitions by their authors are actually describing the diagnostic criteria for a trigger point, as does the IUGA/ICS proposed definition. “A hyperirritable spot in skeletal muscle that is associated with a hypersensitive palpable nodule in a taut band”(4)

Myofascial trigger point “discrete, hyperirritable nodule in a taut band of skeletal muscle that is palpable and tender during a physical examination.” (5)

Old definition: “ A hyperirritable spot, usually within a taut band of skeletal muscle or in the muscle’s fascia that can give rise to characteristic referred pain, tenderness and autonomic phenomena.” (6)

Perspectives and controversies: A distinction between active and latent trigger points was not addressed in the 2016 IUGA/ICS paper. The IUGA/ICS statement about trigger points in the section on pelvic floor muscle function signs is incorrect. It states that the taut band should be tender and that is not found in any definition of listing of diagnostic criteria. There is to be a specific spot within the band not the whole band. Myofascial trigger points are considered a common physical finding on examination of patients with various pain complaints. To date the pathophysiology of the myofascial trigger point remains elusive. Other than palpation there are no currently accepted criteria for finding or describing a myofascial trigger point. Travell and Simons’ technique to diagnose a myofascial trigger point is by palpating the suspected muscle perpendicular to its muscle fiber orientation to locate the taut band. Once the taut band is located palpation within the taut band is done to identify the area of hardness that is most resistant to compression and is the most sensitive.(7) There are three criteria that are essential to the diagnosis of a myofascial trigger point: taut band within a muscle, exquisite tenderness at a point on the taut band and reproduction of the patient’s pain. (7) Besides palpation during a meticulous physical examination diagnosis of a myofascial trigger point was dependent upon the clinical history. A correct diagnosis of a trigger point is determined by the clinician’s training, insight, experience and palpation skills. (5) Utilizing the diagnostic criteria of the presence of a taut band, sensitive spot, local twitch response and referred pain has been show in recent studies to have moderate to excellent reliability. (8,9)

Over the years there have been various descriptions of muscle pain in other languages. Muskelhärten is a German term that means muscle indurations and is describing the palpable hardness of a tender nodule that is the cause of the patient’s pain. (10) Another German term is myogelosen is used to describe the same condition and is frequently used interchangeably with the muskelhärten term. (10)

As with all aspects of diagnosis within medicine objective diagnostic criteria are desired. Advances are being made for diagnosing myofascial trigger points but will probably not make it into the everyday clinic environment secondary to expense. A taut band and the associated local twitch response can be seen on ultrasound. (11) Chen et al utilized magnetic resonance elastography (MRE) to assess the correlation of clinician-identified myofascial taut bands with their presence and characteristics. (12) In their conclusion they felt that clinicians might overestimate and MRE would underestimate the presence of taut bands but that they do exist, can be evaluated quantitatively and are associated with localized areas of increased stiffness in the muscle. (12) A tissue compliance meter which measures stiffness in the taut band has been shown to confirm the hardness of the discrete band of muscle that harbors the tender region in peripheral skeletal muscle. (2)

Electromyography (EMG) can be used to identify myofascial trigger points but is not useful in a clinical situation secondary to its availability and expense. A signature EMG signal has been described in association with a myofascial trigger point. The electromyographic signal associated with a trigger point is described as a “persistent, low-amplitude, high-frequency discharge” and is labeled as spontaneous electrical activity. (13, 14, 15) This is found only in the area of an active myofascial trigger point.

Shah et al utilized a microdialysis needle to collect physiologic saline that had been exposed to the internal tissue milieu of a myofascial trigger point. (16) In the area of the myofascial trigger point there was a greater concentration of noxious stimulants that included protons, bradykinin, calcitonin gene related peptide, substance P, tumor necrosis factor-α, interlukin-1β, serotonin, and norepinephrine. In another study Shah et al investigated the biochemical milieu of the upper trapezius muscle in subjects with active, latent or absent myofascial trigger points and contrasted this with the noninvolved gastrocnemius muscle. (17) They found that the various biochemicals that are associated with pain and inflammation are elevated in the soft tissue in the area of a myofascial trigger point. As in the previous study, the concentrations of noxious substances including, protons, bradykinin, substance P, calcitonin gene related peptide, tumor necrosis factor-α, interlukin-1β, interlukin-6, interlukin-8, 5-HT and norepinephrine were greater in the area of the trigger points. These substances were also found to be elevated in the gastrocnemius muscle of those with active trigger points in the upper trapezius and differed from those subjects without active trigger points.

1. Bo K, Frawley HC, Haylen BT, et al. An International Urogynecological Association (IUGA)/ International Continence Society (ICS) joint report on the terminology for the conservative and nonpharmacological management of female pelvic floor dysfunction. Neurourol Urodynam 2016; 9999: 1-24.

2. Doggweiler R, Whitmore KE, Meijlink JM, Drake MJ, Frawley H, Nordling J, Hanno P, Fraser MO, Homma Y, Garrido G, Gomes MJ, Elneil S, van de Merwe JP, Lin AT, Tomoe H. A standard for terminology in chronic pelvic pain syndromes: A report from the chronic pelvic pain working group of the international continence society. Neurourol Urodyn. 2017 Apr;36(4):984-1008. doi: 10.1002/nau.23072. Epub 2016 Aug 26.

3. Fernandez-de-las-Penas C, Dommerholt J. International Consensus on Diagnostic Criteria and Clinical Considerations of Myofascial Trigger Points: A Delphi Study. Pain Medicine, 2017; 0: 1-9.

4. Simons DG, Travell JG, Simons LS. Myofascial Pain and Dysfunction: The Trigger Point Manual Vol. 1 Upper Half of Body. 2nd ed. Baltimore: Williams & Wilkins; 1999.

5. Shah JP, et al. Myofascial Trigger Points Then and Now: A Historical and Scientific Perspective. PM R, 2015:7(7):746-761.

6. Travell JG, Simons DG. Myofascial Pain and Dysfunction: The Trigger Point Manual Vol. 1 The Upper Extremities. Baltimore: Williams & Wilkins; 1983.

7. Gerwin RD. Diagnosis of Myofascial Pain Syndrome. Phys Med Rehabil Clin N Am, 2014: (25):341-355.

8. Mora-Relucio, Nunez-Nagy S, Gallego-Izquierdo T, et al. Experienced versus inexperienced interexaminer reliability on location and classification of myofascial trigger point palapation to diagnose lateral epicondylalgia: An observational cross-sectional study. Evid Based Complement Alternat Med 2016; 606597 19.

9. Sanz Dr, Lobo Dl, et al. Inter-rater reliability in the clinical evaluation of myofascial trigger points in three ankle muscles. J Manipulative Physiol Ther 2016;39:623-34.

10. Mense S, Simons DG. Muscle Pain Understanding Its Nature, Diagnosis, and Treatment. Philadelphia: Lippincott Williams & Wilkins; 2001.

11. Sikdar S, et al. Assessment of myofascial trigger points (MTrPs): a new application of ultrasound imaging and vibration sonoelastography. Proceedings of the 30th annual International IEEE EMBS Conference. Vancouver (Canada): 2008.

12. Chen Q, et al Quantification of myofascial taut bands. Arch Phys Med Rehabil. 2016: 97:67-73.

13. Hubbard DR, Berkoff M. Myofascial trigger points show spontaneous needle EMG activity. Spine. 1993: 18:1803-1807.

14. Simons DG, Hong CZ, Simons LS. Prevalence of spontaneous electrical activity at trigger points and at control sites in rabbit skeletal muscle. J Muscoskel Pain. 1995:3(1):35-48.

15. Hong CZ, Simons DG. Pathophysiologic and electrophysiologic mechanisms of myofascial trigger points. Arch Phys Med Rehabil. 1998: 79:634-640.

16. Shah JP, et al An in vivo microanalytical technique for measuring the local biochemical milieu of human muscle. J Appl Physiol. 2005:99:1977-1984.

17. Shah JS, et al Biochemicals associated with pain and inflammation are elevated in sites near to and remote from active myofascial trigger points. Arch Phys Med Rehabil. 2008:89:16-23.

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