Trigger Points Introduction

(Excerpts from Trigger Point Manual [1])






2       Theoretical Thinking (Possible Explanations of Trigger Point Phenomena) 3

3       Trigger Point Examination. 4

4       Alternative Treatment Techniques. 5

5       Literature Review.. 5






1.1   Introduction

1.1.1   A Myofascial TP is a hyperirritable focal point within a taut band of skeletal muscle fibers. On compression, it can evoke typical referred pain and autonomic phenomena. A Myofascial TP is located in skeletal muscle and its associated fascia distinguished from a TP in other tissues such as skin, ligament and periosteum. 

1.1.2   Trigger Points can be either active or latent. Active Trigger Points cause pain, restriction of movement and muscular weakness. Latent trigger points cause restriction of movement and muscular weakness but DO NOT cause pain.  Latent TPs can remain in muscle tissue for years after apparent injury recovery yet remain clinically silent until activated by minor overstretching, overuse or chilling of the muscle when an acute attack of pain ensues. Both Active and Latent TPs cause dysfunction but only active TPs cause pain.

1.1.3   Healthy muscle tissue does not contain TPs, which means there are no taut bands, focal tenderness or pressure induced pain referral and local twitch responses.

1.1.4   Although both sexes and all ages can develop TPs sedentary, middle-aged women who engage in novel, repetitive or over activity are very vulnerable [2]. Excepting later years, women are more prone to trigger points than men are. Sola[3] Solberg [4] Agerberg [5]

1.1.5   Women are also more likely than men to seek medical assistance for TP related pain. Kraft [6] The dental field reports more female than male patients with TPs and in three studies report 79%-84% of the TP pain related patients were women. [7] [8] [9]

1.1.6   Children can also develop trigger points. Bales [10]

1.1.7   The frequency of Active TPs increases with age and level of activity into the most active middle years with diminishing TP prevalence in later years where chief symptoms are the stiffness and restricted motion of latent TPs. Travell [11]

1.1.8   Postural muscles (Neck, Shoulder & Pelvic Girdles) and masticatory muscles are most likely to develop TPs.

1.1.9   Common muscles, which develop TPs, are the upper Trapezius, scalene, Sternocleidomastoid, Levator scapulae and quadratus lumborum.


1.2.1   Introduction                 These clinical characteristics are listed in the order one is likely to discover them during examination and provides an operational definition of Myofascial Trigger Points.                 Finding a site of local tenderness {Number 5) is essential to the diagnosis, but non-specific. Numbers 6 and 7, a local twitch response and pain reproduction, when present, is specific and diagnostic of a Myofascial TP. The more of the remaining findings that are present, the more certain is the diagnosis, which may be recorded as Myofascitis of specific muscles for administrative or insurance purposes.

1.2.2   Criteria                 History of sudden onset during or shortly following acute overload    A history of sudden onset during or shortly following acute overload stress, or a history of gradual onset with chronic overload of the affected muscle;                 Characteristic patterns of pain    Characteristic patterns of pain that are referred from myofascial TPs, patterns that are specific to individual muscles;                 Weakness and restriction    Weakness and restriction in the stretch range of motion of the affected muscle                 A taut, palpable band    A taut, palpable band in the affected muscle                 Exquisite, focal tenderness    Exquisite, focal tenderness to digital pressure (the TP), in the band of taut muscle fibers                 Local twitch response    A local twitch response elicited through snapping palpation or needling of the tender spot (TP)                 Reproduction of the patient's pain    The reproduction of the patient's pain complaint by pressure on, or needling of, the tender spot (TP)                 Elimination of symptoms    The elimination of symptoms by therapy directed specifically to the affected muscles

2      Theoretical Thinking (Possible Explanations of Trigger Point Phenomena)

2.1   Summary

2.1.1   Acute Muscle Strain                 The contractile elements in a portion of the muscle are overloaded resulting in tissue damage which includes tearing of the sarcoplasmic reticulum. This releases stored calcium. Because the sarcoplasmic reticulum is damaged, it cannot reabsorb calcium ions. Sustained contraction is the result of this lack of calcium ion re-absorption. Chronic stress and excessive fatigue combined with continued contraction of the muscle may result in further damage to the muscle cell repeating this process.

2.1.2   Sustained Muscle Contraction                 The ATP energy supply combined with excess calcium results in sustained Contracture of the muscle fibers producing a region of uncontrolled metabolism within the muscle tissue. Severe local vasoconstriction may result because of a TP mediated reflex response via the central nervous system and sympathetic nervous system fibers.

2.1.3   Increased Metabolism with Decreased Circulation                 Metabolic demand is increased when muscle fibers continually contracted but circulatory supply is decreased by sympathetic nervous system mediated vasoconstriction. The muscle fibers passing through this region become taut and are strongly shortened independent of propagated action potentials. These taut fibers may be what is palpated as a band in the muscle.

2.1.4   Questions and Problems                 The tautness of the bands, when examined clinically suggests that at least half the total fiber length is contracted. The mechanism with which the Contracture of the sarcomeres might propagate along each fibre is not clear since muscle cells that may not have sarcoplasmic reticulum damage are also contracted.                 Excess calcium should diffuse through the tissues within hours or days and lose its effectiveness. This would make it difficult to explain how active and latent trigger points persist for a much longer period.

2.1.5   Explanation for sustained contraction                 Total depletion of ATP could lead to conditions similar to other disease processes which cause muscle Contracture with electrical silence such as McArdle's Disease,  Carnatine Deficiency, and Rigor Mortis. The processes of these diseases may explain this sustained contraction.                 ATP depletion results in the myosin heads not releasing from the actin filaments and thus the sarcomeres become rigid at that length. For this explanation a central region of this ATP deficit contracture must be surrounded by a region of runaway metabolism to insure that the ATP was not replenished.

2.1.6   Nerve sensitising substances Released                 Serotonin, kinins and prostaglandin may be released in the TP zone by several mechanisms. Tissue injury may result in some blood extravasation as observed by Awad [12].                 More research is needed to determine whether the initial phase of increased metabolism with reduced circulation would create a local accumulation of metabolic products resulting in the release of prostaglandins and or other sensitising substances.

2.1.7   Dystrophic Changes                 Dystrophic changes have been reported [13] similar to those induced experimentally by muscle ischemia [14]. Prolonged regional ischemia of critical intensity combined with runaway energy demands may result in these dystrophic changes.

3      Trigger Point Examination

3.1   Flat Palpation

3.1.1   Using the padded aspect of the fingers or thumb and proceeding at a right angle across the muscle fibers while pressing them against the underlying tissue or bone.

3.1.2   When trigger points exist taut bands, exquisite, focal tenderness (Trigger Points), and a twitch response will be detected.

3.2   Pincer Palpation

3.2.1   The muscle or muscles are rolled between the tips of the digits to detect taut bands of fibers, to detect exquisite, focal tenderness (Trigger Points), and to elicit local twitch responses.

3.3   Snapping Palpation

3.3.1   Locate a taut band of muscle and place fingertip at right angles. Begin moving your fingers back and forth to roll the underlying fibers under the finger. This is just as plucking a guitar string except contact with the surface is maintained. The purpose of this method is to elicit a local twitch response and is most effective when done near or on the trigger point with the muscle at a neutral length or slightly lengthened.

4      Alternative Treatment Techniques

4.1   Ischemic Compression

4.1.1   Progressively stronger pressure is applied with the digits or elbow until the trigger point tenderness subsides. At first the tissues blanch and then become hyperaemic (Flushed) on release of the pressure.

5      Literature Review

5.1   Characteristics of Patient Population

5.1.1   Sola reports that among 200 asymptomatic 17 to 35 year old subjects, 54% of the women and 45% of the men had latent trigger points in the shoulder-girdle muscles. However, of the 100 subjects in each group, practically equal numbers, 13 female and 12 male subjects, experienced referred pain in response to pressure on the TPS.

5.1.2   Solberg reports that, a group of 739 college students were studied for evidence of masticatory apparatus dysfunction. A significantly greater number of female than male students had headaches and were aware of temporomandibular joint sounds, indicative of the Myofascial pain-dysfunction syndrome associated with TPs. Other questions relating to masticatory pain and dysfunction were answered without evidence of sex distinction. Twice as many women as men had tenderness of the lateral Pterygoid muscle.

5.1.3   Agerberg studied 194 persons, who comprised a random sampling of 70-year-old male and female residents of a town in Sweden, who showed no appreciable sex difference in the frequency of pain and dysfunction of the masticatory system.

5.1.4   Kraft reported on 91 patients who were referred to a Physical Medicine and Rehabilitation Service and who were diagnosed as suffering from "fibrositis syndrome, 69 were women and 22 were men.

5.1.5   Bales observed Infants with point tenderness of the rectus abdominis muscle and colic, both of which were relieved by sweeping a stream of vapocoolant over the muscle, which helps to inactivate myofascial TPs. When children were examined for them, myofascial TPs were found to be a common source of Musculoskeletal pain in childhood.

5.1.6   Travell reported in a personal communication with Sola AB who found that laborers, who exercise their muscles heavily every day, are less likely to develop active TPs than are sedentary workers who tend to indulge in occasional orgies of vigorous physical activity. Travell reports similar experience.

5.2   Metabolism of Trigger Points

5.2.1   Awad observed blood extrvasation in the TP zone which included large number of platelets that are a source of serotonin. This is not only a sensitising agent, but also causes local ischemia. He also observed degranulating mast cells, which release histamine.

[1] Travell Janet G., Simons David G.(1983).Myofascial pain and dysfunction-the trigger point manual .428 E. Preston Street Baltimore, Md 21202, U.S.A:Williams & Wilkins.

[2] Travell Janet G., Simons David G.(1983).Myofascial pain and dysfunction-the trigger point manual .428 E. Preston Street Baltimore, Md 21202, U.S.A:Williams & Wilkins. Page 13

[3] Sola AB, Rodenberger ML, Gettys BB: Incidence of hypersensitive areas in posterior shoulder muscles. Am J. Phys Med 34:585-590, 1955.

[4] Solberg WK. Woo MW, Houston IB: Prevalence of mandibular dysfunction in young adults. 1 Am Dent Assoc 98:25-34. 1979.

[5] Agerberg G, bsterberg T: Maximal mandibular movements and symptoms of mandibular dysfunction in 70-year-old men and women. Swed Dent J 67:147-163.1974.

[6] Kraft GH, Johnson EW, LaBan MM: The fibrositis syndrome. Arch Phys Med Rehabil 49:155- 162, 1968.

[7] Butler IH, Folke LEA, Bandt CL: A descriptive survey of signs and symptoms associated with the myofascial pain-dysfunction syndrome. ] Am Dent Assoc 90:635-639, 1975.

[8] Cohen SR: Follow-up evaluation of 105 patients with myofascial pain-dysfunction syndrome. J Am Dent Assoc 97:825-828, 1978.

[9] Sharav Y, Tzukert A, Refaeli B; Muscle pain index in relation to pain, dysfunction, and diz- ziness associated with the myofascial pain-dys- function syndrome. Oral Surg 46;742-747, 1978.

[10] Bales T, Grunwaldt E: Myofascial pain in childhood. J Pediatr 53:198-209, 1958.

[11] Travell Janet G., Simons David G.(1983).Myofascial pain and dysfunction-the trigger point manual .428 E. Preston Street Baltimore, Md 21202, U.S.A:Williams & Wilkins. Page 13

[12] Awad EA: Interstitial myofibrositis: hypothesis of the mechanism. Arch Phys Med 54:440-453, 1973.

[13] Miehlkc K, Schulze G, Eger W: Klinischc und experimcntelle Untersuchungen zum Fibrositis syndrom. Z Rheumaforsch 19:310-330, 1980.

[14] Stenger RI. Spiro D. Scully RE, Shannon IM: Ultrastructural and physiologic alterations in ischemic skeletal muscle. Amer J Patho140:1-20. 1962.