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Chinese Medical Journal 2014;127 (24) 1
DOI: 10.3760/cma.j.issn.0366-6999.20141999
Department of Rehabilitation, Guangxi National Hospital, Nanning,
Guangxi 530001, China (Zhuang XQ and Tan SS)
Department of Sport Medicine and Pain Clinic, Center of Sports
Rehabilitation, School of Sport Science, Shanghai University of
Sport, Shanghai 200438, China (Huang QM)
Correspondence to: Huang Qiangmin, Department of Sport Medicine
and Pain Clinic, Center of Sports Rehabilitation, School of Sport
Science, Shanghai University of Sport, Shanghai 200438, China (Tel:
86-21-51253357. Email: huaqia404@aliyun.com)
This study was supported by grant from Ministry of Education and
the provincial open fund of Sports University of Shanghai, and Key
Laboratory of Exercise and Health Sciences (Shanghai University of
Sports).
Conict of interest: none.
Review article
Understanding of myofascial trigger points
Zhuang Xiaoqiang, Tan Shusheng and Huang Qiangmin
Keywords: myofacial pain syndrome; myofascial trigger points; etiology; pathology; diagnosis; treatment
Objective To investigate the current practice of myofascial pain syndrome (MPS) including current epidemiology,
pathology, diagnosis and treatment.
Data sources The data analyzed in this review were mainly from relevant articles without restriction on the publication
date reported in PubMed, MedSci, Google scholar. The terms “myofasial trigger points” and “myofacial pain syndrome”
were used for the literature search.
Study selection Original articles with no limitation of research design and critical reviews containing data relevant to
myofascial trigger points (MTrPs) and MPS were retrieved, reviewed, analyzed and summarized.
Results Myofascial pain syndrome (MPS) is characterized by painful taut band, referred pain, and local response twitch
with a prevalence of 85% to 95% of incidence. Several factors link to the etiology of MTrPs, such as the chronic injury
and overload of muscles. Other factors, such as certain nutrient and hormone insufciency, comorbidities, and muscle
imbalance may also maintain the MTrP in an active status and induce recurrent pain. The current pathology is that an extra
leakage acetylcholine at the neuromuscular junction induces persistent contracture knots, relative to some hypotheses of
integration, muscle spindle discharges, spinal segment sensitization, ect. MTrPs can be diagnosed and localized based on
a few subjective criteria. Several approaches, including both direct and supplementary treatments, can inactivate MTrPs.
Direct treatments are categorized into invasive and conservative.
Conclusion This review provides a clear understanding of MTrP pain and introduces the most useful treatment
approaches in China.
Chin Med J 2014;127 (24):
2014-1999 P7
Most pains are often associated with myofascial pain
syndrome (MPS), which is caused by myofascial
trigger points (MTrPs). The prevalence of MTrPs was
reported by 85% of patients visiting a tertiary pain clinic1
and even 95% of people with chronic pain disorders
involving MTrPs.2 As many as 9 million people in
the United States suffer from such illness.3 MTrPs are
hyperirritable spots located at the muscle, fascia, or
tendinous insertions, in which the local pain is perceived
as deep and aching in palpable taut band, referred pain in
the same or a distant position, and local twitch responses
(LTRs) in forceful palpation and/or needling.4,5 All types of
population can suffer from MPS, especially individuals who
often participate in sports6,7 and those who experience age-
related degeneration.8,9 The pain of almost all orthopedic
disorders is involved in this category.10,11 Numerous studies
have conrmed that several pain syndromes are associated
with the activation of MTrPs in the skeletal muscles.12-14
In clinical practice, MTrPs can be classified into either
latent or active.4,6 Active MTrPs are both tender and
spontaneously painful, whereas the latent ones are tender
without spontaneous pain.4,6,15 This pain syndrome can be
primary MTrPs from an old muscle injury or secondary
from other disorders.5,16 The pain from MTrPs can be
alleviated through various clinical therapies, which render
them inactive.4,5,17
Etiology of MTrPs
In studying MTrPs in newborn infants and young children,
a latent trigger point can be identied in some muscles after
the age of 4 years.18,19 Therefore, the onset of MPS depends
on whether or not the latent MTrP exists. The etiology of
MTrP often includes precipitating and perpetuating factors
(Table 1), which can concurrently exist in a patient.
Various traumas, such as contusions, sprains, and strains,
may induce acute MTrPs. The onset of these trigger points
may be initiated by repetitive micro-injuries, including the
overloading and overuse of muscles, which often heighten
chronic MTrPs.20,21 According to the principle of muscle
fiber size, a low load force acting on a joint or spine for
a long time can cause myalgia.21 When maintaining a
continuous static loading, type I smaller muscle bers are
initially recruited and then rolled off. Hence, this type of
muscle fibers, which are called Cinderella fibers, can be
Chin Med J 2014;127 (24)
2
easily injured.20,21 MTrPs frequently occur in this type of
muscle bers that have more ratios within the muscles for
postural maintenance.22 In this event, the upper trapezius
and levator scapulae can also readily acquire injury; in these
two muscles, MTrPs can often be generated.23 The aging
degeneration of musculoskeletal system, with the gradual
loss of myofascial exibility, is vulnerable and eventually
results in active MTrPs.9,24 A certain compression or non-
bacterial inflammation of the spinal column may irritate
the nerve root, causing the sensitization of the spinal
segment and active MTrPs in the innervated muscles.25,26
Emotional stress can increase sympathetic output and sleep
deprivation, considerably increasing muscle tension and
fatigue, including anxiety and insomnia, and decreasing the
pain threshold.4,5 Endocrine and metabolic deciencies and
thyroid and estrogen insufficiencies can irritate the latent
MTrPs to be active.4,5 Meanwhile, nutritional deficiencies
from vitamins and minerals, especially B12, C, folic acid,
iron, and calcium, may perpetuate the activeness and
recurrence of MTrPs.5,27 Moreover, chronic infections, such
as viral, parasitic, and fungal infection, may perpetuate the
activity of MTrPs.5,28
Skeletal muscles may be classified into two categories
according to their functions, dynamics, and postural
requirements.22,29,30 Accordingly, a sedentary lifestyle, in
which one spends more time in static postures than in
motion, can progressively inhibit dynamic muscles and
cause tightness and inexibility in postural muscles. In this
event, a biomechanical imbalance between the dynamic and
postural muscles may gradually develop. When a muscle
generates MTrP, the local mechanical balance worsens.30
Moreover, if the pain of the muscles is untreated for a long
time or is repeatedly activated, a chronic biomechanical
imbalance is maintained and secondary MTrPs gradually
develop in other muscles. Thereafter, an entire joint
dysfunction (e.g., periarthritis of the shoulder) may possibly
emerge.31
Pathology of MTrPs
Histopathology
The taut bands of muscles are common contracture
fascicles with MTrPs and TrPs.5,12 Huang et al32 observed
a number of contracture knots gathered together in the
longitudinal section of MTrPs. This observation conrmed
the assumption of Simons et al. regarding the hypothetical
sketch of contracture knots of MTrPs.5,33 In the observed
cells, the mitochondrial numbers decreased and the nucleus
of the cells moved into the middle.34
Based on these results of both clinical and morphological
features, MTrPs are speculated as a complex, that is, central
MTrPs (cMTrPs) and attachment MTrPs (aMTrPs).5,33
cMTrP is a painful nodule along taut band in the muscle
belly (Figure 1). Meanwhile, aMTrPs are also painful
places in the combination between muscle and its tendon
as well as the tendon attachment to the bone, which often
link to an enthesiopathy and tenosynovitis;35 the typical
aMTrP appears as a cyst of the tendon sheath and narrow
tenosynovitis.36
Pathophysiology
Studies on MTrPs in the previous century reported a high
frequency of spontaneous electrical potentials (SEA)5,33,37
and contracture knots in the skeletal muscles of animals
and human.38 Simons et al5 speculated that acetylcholine
(ACh) abnormally increased at the neuromuscular junction
in MTrPs. Local contracture knots were generated by
injecting an anti-acetylcholine esterase into a local normal
muscle.38 Therefore, the hypothesis of extra-leakage ACh
at the nerve endings in motor endplates was proposed.5,33,38
The literature review indicated that several theories are
related to this occurrence on MTrPs.
Hypothesis of integration
This hypothesis posits that an extra leakage of ACh at
the nerve endings causes a failure in the local motor
endplate function. In particular, the leakage excites the
ACh receptors of postsynaptic membrane, produces local
continual depolarizations, and prompts the sarcoplasmic
reticulum to release large amounts of calcium.5,33 These
procedures result in the sustained contracture knots of
muscle fibers and increased muscle tone by shortening
sarcomeres.5,15,39,40 In this condition, the muscle bers at the
nerve endings become cramped, causing local ischemia and
hypoxia with increasing local metabolic requirement.5,33
Meanwhile, the concentrations of serotonin, histamine,
bradykinin, and substance P increase in the surroundings
of the contracture knots,41 aggravate the local ischemia, and
sensitize the afferent nerves. These occurrences result in
MTrP pain and local sympathetic symptoms.5,42 Moreover,
these pathological changes induce a feeling of local cold
(vasoconstriction),43 anxiety, and mental stress.4,5,44
Table 1. Etiological factors of MTrPs
Precipitating factors Perpetuating factors
Various traumas Endocrine and metabolic deciencies
Repetitive micro injuries and
overload injuries
Nutritional deciencies (certain vitamins
and elements), anemia
Mechanical injuries Chronic Infection
Ageing structural degeneration of
bones and joints
Chronic biomechanical imbalance
Certain compression or non-bacteria
Inammation of spinal column
Repetitive bad posture, bad working
environment
Emotional stress
Figure 1. Structural graphic of myofascial trigger point. cMTrP
refers to the central MTrP and aMTrP denotes the attachment
MTrP. A muscle directly attaches to a bone (right side) and via a
tendon to the bone (left side).
Chinese Medical Journal 2014;127 (24) 3
A dysfunctional motor endplate in MTrPs has numerous
small loci,45,46 including the sensory and motor loci,5,47 such
as “sensitive locus” and “active locus”.48 The sensitive
locus is a receptor for pain and local twitch response,
and is also a site for the sensitization of nerve endings,
which distribute throughout all muscles.48 Active loci are
contracture knots, which can be recorded as the SEA with
high frequency of low amplitude potentials.5,34,45,48,49 Among
these potentials, some intermittent abnormal high amplitude
potential bursts emerge.32,34
Hypothesis for muscle spindle discharges
Conducting electromyography (EMG) studies allows
the identification of two types of independent electrical
potentials at the location of MTrPs; one type is the low
potentials with amplitude of approximately 10 µV to 80
µV, and the other is the high potentials with amplitude of
approximately 100 µV to 600 µV with both normal and
abnormal wave shapes.32,34,37 Several scholars deemed that
the high spike of abnormal discharges recorded from the
location of MTrPs may emerge from the muscle spindle
stimulated by an excited sympathetic nerve.37,42 This
hypothesis implies that the MPS symptoms are likewise
associated with autonomic nervous irritation.
Hypothesis of central or spinal segment sensitization
Central theories or spinal segment sensitization focus on
developing the central sensitization of the spinal segment
dorsal and motor horn cells through the persistent noxious
input if MPS is left untreated.5,50,51 Whether central
sensitization causes MTrPs or merely perpetuates and
amplifies them remains an issue. When active MTrPs
exist, a constant nociceptive input into the dorsal horn
emerges, thus increasing an excitability of neuron in
the dorsal horn and enlarging neuron receptors pool to
perpetuate the altered motor control strategies. This central
sensitization increases muscle tone and chronic mechanical
imbalance.52,53 Therefore, this hypothesis explains why the
referred pain and local response twitch can occur in the
MTrPs controlled by the spinal cord.
Hypothesis of scar and brosis in the muscles
Several scholars in the early 20th century considered scar
brosis as the cause of a string of indurations in muscles.54
Chinese scholars discovered some biochemical changes,
including a high concentration of bradykinin, serotonin,
and substance P, in these soft tissues and their surroundings
after acute or chronic injuries.33 In the repairing period,
the scar, adhesion, and spasm of muscles or soft tissues, as
well as a microcirculation block in the region of lesions,
were formed due to several pathological and physiological
processes.55 Based on this theory, Chinese doctors obtained
positive effects on treating numerous pain syndromes
using the needle mini-knife therapy.55 This hypothesis was
later substituted by other hypotheses on MTrPs due to the
lack of further studies on tissue morphology and electrical
physiology.
Relationships between MTrPs and acupoints
Some scholars recently investigated 255 MTrPs and
compared them with the traditional acupoints.56,57 They
reported that 92% of the trigger points corresponded to the
acupoints in the anatomical position, 79.5% were related to
the acupoints in clinical indications, and 76% of the referred
pain distributions of MTrPs corresponded to the meridian
running. However, the proposition of Trevell and Simons
on trigger points is different from the acupoints map of
the traditional Chinese medicine. The location of trigger
points is based upon different individuals, and the referred
pain relies on the severity of the disorder. From a clinical
viewpoint, the trigger points that are diagnosed today must
be assumed similar to the ancient Chinese acupoints, which
were developed before the Song dynasty.58 Prior to the
Song dynasty, the acupoints were localized according to the
running of meridian similar to the case of human fascia.58
Diagnosis and localization of MTrPs
Once the MTrPs are activated, the patient can feel a local
pain and musculoskeletal dysfunction with autonomic
nervous symptoms and a series of other syndromes in the
joints or visceral organs.5 In the previous century, Trevell
realized that a certain pain area complained by a patient
was not always at the site where the pain originated. This
pain was a referred pain associated with MTrPs.59 Other
than the referred pain, a hard nodule is painful with a
palpation in approximately 2 kg to 6 kg compression.60 This
nodule is a sensitive area along the taut band that is often
associated with an intolerable pain or obvious soreness and
swell feeling.39 Once the latent MTrPs become activated,
the referred pain in some MTrPs emerges in another
place, not following a distribution of nerve running.3 9
While puncturing the MTrPs, a muscle jump (local twitch
response), withdrawal response, or needling referred pain
can be elicited by needling,5,39,61 indicating that the MTrPs
localized by a palpation is certain.
An effective treatment of MPS requires the inactivation of
MTrPs. Therefore, accurately localizing the MTrPs plays
an important role in treating MPS. According to some
subjective criteria and distributions of referred pain for
diagnosis provided by Simons et al, the clinical diagnosis of
MTrPs is typically based on the following steps:5,39,61
Diagnosis of affected muscles
Histories and physical examinations are helpful in
treating MPS. In particular, a clinician or therapist must
determine which muscle of the patient is affected and
which precipitating and perpetuating factors are related
to such pain. The symptoms and signs of MPS generally
depend upon the location of the MTrPs in the affected
muscles, such as headache and dizziness in neck muscles,13
dysfunction and pain of shoulder in the muscles of
surrounding scapula and humerus,7 and menorrhalgia
in abdominal and pelvic muscles.62,63 In most cases, the
symptom of fear of cold in the local region often emerges.
In this event, the range of motion of the affected muscles
is limited, and muscle strength is weak. Moreover, active
MTrPs, particularly the MTrPs in the neck muscles, may
Chin Med J 2014;127 (24)
4
interfere with the sleeping pattern or condition of the
patient.44
Localization of MTrPs
A guidance of the rough distribution of the referred pain
from MTrPs, which was sketched by Simons et al,5 and
subjective criteria elucidated that (a clear referred pain and
tenderness with the muscle tension and palpable nodule,
local twitch response)5,64 the trigger point in the affected
muscle can be localized by a finger of inspector. A deep
pressure may sometimes induce a pressing referred pain.60
Each MTrP has its own characteristic scope of referred
pain, but it may not completely run in accordance with the
sketch produced by Simons et al5. In numerous cases, the
MTrP may be secondary to chronic orthopedic or other
disorders.
Objective indicators
MTrPs can be examined through EMG with the
spontaneous electrical activity65 and by employing magnetic
resonance imaging and ultrasound with a thickening
image.5
The diagnosis of chronic myalgia is another issue that is
regarded as the biomechanical imbalance of neuromuscular
system in local region.64 Therefore, a clinician or therapist
is required not only to understand the characteristics of
the active trigger points in a muscle but also to carefully
check for the presence of other MTrPs in the antagonistic
or synergistic muscles. In the treatment, all MTrPs should
be considered. Muscle jump and referred pain of needling
indicate the correct location of MTrPs found by clinician or
therapist.
Treatment of MTrPs
The MTrP treatment aims to inactivate the trigger points.
Multidisciplinary approaches, which comprise direct
approaches, inactivate the MTrPs, consequently decreasing
the muscle tone. Meanwhile, supplementary approaches
correct the biomechanical imbalances of the local
muscles. These approaches include needling, stretching,
psychiatric therapies, massage and hand manipulation,
chiropractic technique, and medications (Table 2). Several
approaches not only directly inactivate the MTrPs but also
consolidate the effects of other therapies as supplementary
treatments.66,67 Chiropractic and exercise approaches may
be applied to correct the biomechanical imbalance of the
musculoskeletal system.
Needling approach
Several needling techniques focus on the MTrPs. If the
trigger points can be accurately punctured, the local twitch
responses of the muscle (a muscle jump) or needling
referred pain occur.5,45
Wet needling
This approach comprises two methods. The first method
involves repeatedly puncturing a syringe needle (gauge
5) into the MTrPs. Once the LTRs with a strong sour
or swelling pain are elicited at a local region, 0.1 ml to
0.2 ml of local anesthetics may be injected to relieve
this sore feeling.68 The beneficial effect of this therapy
is the lessening of the acute or chronic pain of MTrPs.68
Meanwhile, the second method of this approach involves
a slight addition of an anesthetic agent (0.3 ml to 0.5 ml),
which is simply injected into the location of a muscle jump.
A local light massage is subsequently administered to allow
the anesthetics to infiltrate the location of the MTrPs.5,69
This approach can considerably avoid the local needling
pain, but its effect is momentary compared with the former.
Hence, the treatment process of this approach must be
repeated. This method is appropriate for some patients who
are overly sensitive and unable to tolerate a needling pain.
Dry needling
This approach comprises several procedures.70,71 First,
if a patient can endure a needling pain, the MTrPs are
repeatedly punctured using an acupuncture needle (Ф
0.3 mm to Ф 0.5 mm) to elicit the LTRs. Second, once a
muscle jump emerges, a needle remains at the location
of the MTrPs for 10 to 15 minutes as an acupuncture
therapy in China. Third, the “Shanzen” is performed. The
“Shanzhen”, which is a treatment practiced in China, is
often associated with the concurrent application of local
hand manipulation and massage. During this approach,
massage and manipulation are initially applied. However,
if some painful nodules and areas are localized and do not
dissipate with the massage, a needle with Ф 0.3 mm is used
to puncture it for a few times into the location of the MTrPs
in a rapid back and forth movement, better with a local
twitch response.
Miniscalpel-needle therapy
This therapy is highly popular and effective in China.
However, this approach is merely employed to cut the
thickening structures in the location of aMTrPs to loosen
the adhesion and contracture hardening capsule of the joint
and ligament.55,71
Massage and hand manipulation
Different from the traditional massage, massage and
hand manipulation require the location of MTrPs.72
Table 2. Treatment approaches of MTrPs
Directly inactive approaches Supplementary approaches
Needling
Wet needling: injection
inltration, repeatedly puncturing
Dry needling: acupuncture way,
repeatedly puncturing, fast needling
“Shanzhen”; Miniscalpel-needle
technique
Muscle stretching
Exercise therapy
Massage and manipulation
Chiropractic technique
Physiatric therapies supercially
laser, ultrasonic wave, infrared light,
microwave, electrical stimulation,
Thermalism, et al.
Cold with muscle stretching
Massage and manipulation
Physiatric therapies deeply
Laser, ultrasonic wave, infrared
light, microwave, shockwave,
electrical stimulation, etc.
Medication
Paracetamol or muscle relaxants,
NSAID drug or COX-2 selective inhibitors,
Narcotic analgesics, Adjuvant analgesics,
antidepressants or anticonvulsants, Chinese
traditional medicine (jinkui shengqiwan and
different di-huang-wan)
Chinese Medical Journal 2014;127 (24) 5
Focusing on MTrPs, all varieties of massage skills may be
applied and are often incorporated with chiropractic and
muscle stretching therapies. If the result of this approach
is ineffective, the needling approach can be applied.
Moreover, massage approaches can serve as supplementary
treatments, which may decrease the uncomfortable response
of needling.
Psychiatric therapies
Deep laser, ultrasonic wave, microwave, infrared light, and
shockwave therapies are recommended to treat MTrPs.36,73
All of these approaches must focus on the trigger points,
rather than on a referred pain. Hence, a psychiatric therapist
must understand the process of localizing MTrPs.
Muscle stretching
Correctly performing muscle stretches can theoretically
relieve a local muscle pain.66,67 However, performing only
muscle stretches may be ineffective in inactivating the
MTrPs of a patient, who has been affected by the pain for a
long period. Therefore, under this approach, the best means
of treating MTrPs is by initially putting the needle, followed
by the application of massage and muscle stretching.
Moreover, this approach requires patients to perform
self-stretching of their affected muscles as homework.
Meanwhile, for some patients, a therapy that uses a cool
spray or cold compress on a certain local region, combined
with muscle stretching, may also obtain a desirable effect to
relieve muscle pain.5,74 Stretching technique is categorized
into two types, namely, self-stretching75 and a stretching
technique that is manipulated by a therapist.66,67
Chiropractic technique
A minor change in spine alignment may induce muscle
tension with pain to some extent. The chiropractic
technique can correct a minor change in the spinal
position.76 The misalignment of the spine can be restored
to the sequences of a normal spinal column. Therefore, the
chiropractic technique can prevent the recurrence of MTrPs
in the muscles that surround the spine or its other parts.
Exercise therapy
Exercise is essential in correcting muscle imbalance to
obtain good therapeutic results after needling the MTrPs
or administering other treatments together with muscle
stretching. Restoring the normal length and flexibility of
the muscles and increasing their endurance are important.
Exercise therapies are classified into two types, namely,
stretching (see above) and strengthening, particularly core
strengthening and stabilization.29 If they are begun too
early, strengthening exercises may cause more pain, spasm,
and tightness. Therefore, these exercises must only begin
after the pain has been fully relieved and must progress to
develop endurance with repetitive low resistance.
Medications
Paracetamol or muscle relaxants may be prescribed
for mild myofascial pain. If these medications are
ineffective, non-steroidal anti-inammatory drugs or cyclo-
oxygenase-2 selective inhibitors may be used, particularly
if the myofascial pain has a local inammatory component.
Narcotic analgesics may sometimes be necessary for
severe myofascial pain. Adjuvant analgesics, such as
antidepressants and anticonvulsants, may be added if the
myofascial pain has a neuropathic component. Somnolence,
which is an attending effect of muscle relaxants, narcotic
analgesics, antidepressants, and anticonvulsants, may be
useful at night for patients with emotional stress and sleep
deprivation. However, relieving pain through the sole use
of medication for a long period is not desirable.
Deficiencies of some vitamins, elements, and hormones
have been associated with musculoskeletal pain and are
thus considered a perpetuating factor. In particular, this
factor often meets a deciency of vitamins B12, D, C, B1,
B6, iron, calcium hypothyroidism, and growth hormone,
which have to be prescribed to the patients.77-79
In Chinese traditional medicine, the musculoskeletal pain is
considered a deciency of “Qi” in kidney. Therefore, two
empirical prescriptions, namely, the Jinkui Shengqi Wan
and different Dihuang Wans, may improve the deciencies
of “Qi” in kidney to help improve a condition of the entire
body of patients.
Summary and conclusion
MPS is a disorder of the musculoskeletal system with
MTrPs in muscles with a prevalence of 85% to 95% of
mobidity. MPS is characterized by painful taut band,
referred pain, and local response twitch. In MTrPs, an
extra leakage of acetylcholine at the neuromuscular
junction induces persistent contracture knots, forming into
a palpable painful nodule, relative to some hypotheses of
integration, muscle spindle discharges, spinal segment
sensitization, scar and fibrosis in the muscles. MTrP is
a complex of both cMTrP and aMTrP. Several factors
link to the etiology of MTrPs; the most commons are the
chronic injury and overload of muscles. Other factors,
such as certain nutrient and hormone insufficiency, some
comorbidities, and muscle imbalance may also maintain the
MTrP in an active status and induce recurrent pain. MTrPs
can be diagnosed and localized based on a few subjective
criteria. In particular, the effective treatment of MPS
depends on a correctable localization of MTrPs and on the
experience of a clinician and therapist. Several approaches,
including both direct and supplementary treatments, can
inactivate MTrPs. Direct treatments are categorized into
invasive and conservative. All treatment approaches must
focus on the location of MTrPs with local twitch responses
and strong sore and swelling pain. This review provides a
clear understanding of MTrP pain and introduces the most
useful treatment approaches in China.
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(Received August 21, 2014)
Edited by Ji Yuanyuan
