AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Background

Myofascial pain (MP) is a common painful disorder responsible for many pain clinic visits. MP can affect any skeletal muscles in the body. Skeletal muscle accounts for approximately 50% of body weight, and approximately 400 muscles make up the body. MP is responsible for many cases of chronic musculoskeletal pain.

MP can cause local or referred pain, tightness, tenderness, popping and clicking, stiffness and limitation of movement, autonomic phenomena, local twitch response (LTR) in the affected muscle, and muscle weakness without atrophy. Trigger points (TrPs), which cause referred pain in characteristic areas for specific muscles, restricted range of motion (ROM), and a visible or palpable LTR to local stimulation, are classic signs of MP. Over 70% of TrPs correspond to acupuncture points used to treat pain.

An active TrP is an area that refers pain to a remote area in a defined pattern when local stimulation is applied. Satellite TrPs appear in response to a primary active TrP and usually disappear after the primary active TrP has been inactivated. Latent TrPs cause stiffness and limitation of ROM but no pain. Frequently, they are found in asymptomatic individuals.

Pathophysiology

A taut band in a muscle may be necessary as a precursor to development of a TrP. Taut bands are common in asymptomatic individuals, but patients with them are more likely to develop a TrP. A latent TrP can develop into an active TrP for a number of reasons. Psychological stress, muscle tension, and physical factors, such as poor posture, can cause a latent TrP to become active.

The pathophysiology of MP is not understood well. Current research supports sensitization of low-threshold mechanosensitive afferents associated with dysfunctional motor endplates in the area of the TrPs projecting to sensitized dorsal horn neurons in the spinal cord. Pain referred from TrPs and LTR may be mediated through the spinal cord after stimulation of a sensitive locus.

Frequency

United States

MP is extremely common, and almost everyone develops a TrP at some time. In the US, 14.4% of the general population suffers from chronic musculoskeletal pain. Approximately 21-93% of patients with regional pain complaints have MP. Studies have demonstrated that 25-54% of asymptomatic individuals have latent TrPs.

Mortality/Morbidity

MP is not a fatal condition, but it can cause significant reduction in quality of life (QOL) and is a major cause of time lost from work. Costs associated with MP sap millions, perhaps billions, of dollars from the economy.

Race

No racial differences in incidence of MP have been described in the literature.

Sex

MP is distributed equally between men and women.

Age

Myofascial TrPs can be found in persons of all ages, even infants. The likelihood of developing active TrPs increases with age and activity level into the middle years. Sedentary individuals are more prone to develop active TrPs than individuals who exercise vigorously on a daily basis.

CLINICAL

Section 3 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

History

Patients usually report regionalized aching and poorly localized pain in the muscles and joints. They also may report sensory disturbances such as numbness in a characteristic of distribution. The type of pain felt is characteristic of the muscle involved. Onset may be acute after a specific event or trauma (eg, moving quickly in an awkward position) or chronic from poor posture or overuse Patients may note disturbed sleep. Those with cervical and periscapular myofascial pain may have been through the "great pillow search" to try to find a comfortable sleeping position. They may or may not be aware of muscle weakness in the affected muscles. They may have a tendency to drop things.

Physical

A skilled examiner can provide accurate diagnosis of MP. Unfortunately, most medical school and residency training programs do not cover this common condition adequately. Locating TrPs is the most important part of the physical examination. TrPs tend to occur in characteristic locations in individual muscles. Travell and Simons' Myofascial Pain and Dysfunction. The Trigger Point Manual is considered the criterion standard reference on locating and treating TrPs.

When the TrP is located, the patient typically has a positive jump sign when local pressure is applied over the area. The jump sign should not be confused with a local twitch response, which is discussed later. The jump sign simply means that the patient jumps from the pain or discomfort in the area that has been palpated. Apply a consistent amount of pressure to the area, as applying too much pressure can elicit pain in nearly all individuals. A pressure algometer (ie, pressure threshold meter) or palpatometer also can be used to standardize the amount of pressure applied.

A taut band is found in the muscle, either by palpation or by needle penetration. It can be distinguished by palpating or by dragging the fingers perpendicular to the muscle fibers. A localized knot or tight ropy area is noted. Patients report that the area is extremely tender when palpated. A localized flinching in the area of the muscle being palpated or local twitch reaction (LTR) may be noted in both active and latent TrPs. Palpation or insertion of a needle into the TrP causes reproduction of the patient's pain and, frequently, sensory complaints. Palpation of either an active or latent TrP causes referred pain in a characteristic area for each muscle as described in Travell and Simons. Sensory disturbance (eg, paresthesias, dysesthesias, localized skin tenderness) may be noted in the same area where pain may be referred. Autonomic phenomena also may be elicited (eg, sweating, piloerection, temperature changes).

• Essential criteria for identifying an active or latent TrP include the following:
• • Palpable taut band if the muscle is accessible
• Exquisite spot tenderness of a nodule in a taut band
• Patient's recognition of current pain complaint by pressure on the tender nodule
• Painful limit to full ROM stretch of the involved muscle
• Confirmatory observations include the following:
• • Visual or tactile identification of LTR
  • Imaging of LTR induced by needle penetration of tender nodule
  • Pain or altered sensation on compression of tender nodule in the distribution expected from a TrP in that muscle
• Electromyography (EMG) demonstration of spontaneous electrical activity (SEA) characteristic of active loci in the tender nodule of a taut band
• Lowered skin resistance to electrical current has been found over active TrPs when compared with surrounding tissue and may be useful in localizing TrPs. Skin resistance normalizes after treatment of TrP.

Causes

Several factors contribute to MP. Abnormal stresses on the muscles from sudden stress on shortened muscles, leg-length discrepancies, or skeletal asymmetry are thought to be common causes of MP. Poor posture also may serve to cause MP. Assumption of a static position for a prolonged period of time also has been implicated in MP. Anemia and low levels of calcium, potassium, iron, and vitamins C, B-1, B-6, and B-12 are believed to play a role. Chronic infections and sleep deprivation have been cited as causative factors, as have radiculopathy, visceral diseases, and depression. Hypothyroidism, hyperuricemia, and hypoglycemia also have been implicated in MP. The pathogenesis likely has a central mechanism with peripheral clinical manifestations.

DIFFERENTIALS

Section 4 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Other Problems to be Considered

Articular dysfunction requiring manual mobilization
Nonmyofascial TrPs
Radiculopathy

WORKUP

Section 5 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Lab Studies

• No specific lab tests confirm a diagnosis of MP, but lab tests can be helpful in looking for predisposing conditions, such as hypothyroidism, hypoglycemia, and vitamin deficiencies. Specific tests that may be helpful include complete blood count, chemistry profile, erythrocyte sedimentation rate (ESR), and levels of vitamins C, B-1, B-6, B-12, and folic acid. A thyrotropin level may be helpful if clinical features of thyroid disease are present.

Imaging Studies

• Infrared or liquid crystal thermography can show increased blood flow, which is sometimes noted at TrPs. Other imaging studies are useful only to rule out other sources of pain generation.

Other Tests

• Needle EMG examination of TrPs in both humans and rabbits has shown high-voltage spike activity and spontaneous low-voltage endplate noise, which is considered characteristic but not pathognomonic. Surface EMG has been used in experiment protocols to monitor muscle activity in TrPs. Ultrasound has been used to visualize the LTR elicited by needle penetration.

Procedures

• TrP injections sometimes are performed with bupivacaine, etidocaine, lidocaine, saline, or sterile water. Occasionally, dry needling is performed without injection of any substance. Steroids may be used in areas possibly associated with inflammation, as in frozen shoulder. Botulinum toxin (BOTOX®) shows promise as a substance that can provide long-lasting relief. The mechanism of its action may be related to blocking of acetylcholine release at the neuromuscular junction of the dysfunctional motor endplates.

Histologic Findings

Contraction knots are a characteristic finding in TrPs, and tender palpable nodules have been recognized since 1951.

TREATMENT

Section 6 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Rehabilitation Program

Physical Therapy

Physical therapy focuses on correction of muscle shortening by targeted stretching, strengthening of affected muscles, and correction of aggravating postural and biomechanical factors. Modalities can be useful to decrease pain to allow participation in an active exercise program.

Corrections of leg-length discrepancies with a heel lift or use of dynamic insoles also may be helpful. Various other techniques and procedures, including the following, have been demonstrated to be effective in some patients:

• Indomethacin phonophoresis
• Massage and exercise
• Stretching
• Electrical muscle stimulation (EMS) using interferential current (IFC) or functional electric stimulation (FES)/electrical nerve stimulation (ENS) or high frequency transcutaneous electrical nerve stimulation (TENS)
• Ultrasound
• EMG biofeedback

Occupational Therapy

Occupational therapy can be helpful in assessing and setting up ergonomically correct workstations. Properly set-up work sites can help to decrease aggravating postural factors.

Medical Issues/Complications

TrPs can be the result of noxious stimuli like a herniated disc. Inquire about such precipitating factors in the patient's environment.

Treatment of TrPs can provide temporary relief of visceral pain referred from other organs and can mask the pain of serious conditions (eg, appendicitis, myocardial infarction).

Complications of TrP injections are rare and depend on the area being injected. They include local pain, bleeding, bruising, intramuscular hematoma formation, infection, and, more rarely, penetration of an underlying organ that could lead to pneumothorax, neural, or vascular injury.

Consultations

Consultation with a specialist in physical medicine and rehabilitation may be indicated and should be arranged as needed.

Other Treatment

• Acupuncture may be helpful.
• Osteopathic manipulation techniques may include integrated neuromusculoskeletal release, myofascial release, strain-counterstrain, muscle energy, and high-velocity/low-amplitude manipulation.

MEDICATION

Section 7 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Muscle relaxant medications and nonsteroidal anti-inflammatory drugs (NSAIDs) at times can be a useful adjunct to active exercise-based treatment, but they are helpful only rarely on their own without an active treatment program. Medications such as low-dose amitriptyline may help to improve the patient's sleep cycle. Botulinum toxin type A injected into TrPs can reduce muscular contractions through the inhibition of acetylcholine release at the neuromuscular junction and appears to have an antinociceptive effect. Current research suggests that peripheral sensitization is blocked, which indirectly reduces central sensitization.

Drug Category: Nonsteroidal anti-inflammatory drugs

Have analgesic, anti-inflammatory, and antipyretic activities. Their mechanism of action is not known, but they may inhibit cyclo-oxygenase activity and prostaglandin synthesis. Other mechanisms may exist as well, such as inhibition of leukotriene synthesis, lysosomal enzyme release, lipoxygenase activity, neutrophil aggregation, and various cell-membrane functions.

Drug Name	Naproxen (Naprosyn, Anaprox, Naprelan)
Description	For relief of mild to moderate pain; inhibits inflammatory reactions and pain by decreasing activity of cyclo-oxygenase, which results in a decrease of prostaglandin synthesis.
Adult Dose	500 mg PO followed by 250 mg q6-8h; not to exceed 1.25 g/d
Pediatric Dose	<2 years: Not established >2 years: 2.5 mg/kg/dose PO; not to exceed 10 mg/kg/d
Contraindications	Documented hypersensitivity; peptic ulcer disease; recent GI bleeding or perforation; renal insufficiency
Interactions	Coadministration with aspirin increases risk of inducing serious NSAID-related adverse effects; probenecid may increase concentrations and, possibly, toxicity of NSAIDs; may decrease effect of hydralazine, captopril, and beta-blockers; may decrease diuretic effects of furosemide and thiazides; may increase PT when taking anticoagulants (instruct patients to watch for signs of bleeding); may increase risk of methotrexate toxicity; phenytoin levels may be increased when administered concurrently
Pregnancy	B - Usually safe but benefits must outweigh the risks.
Precautions	Category D in third trimester of pregnancy; acute renal insufficiency, interstitial nephritis, hyperkalemia, hyponatremia, and renal papillary necrosis may occur; patients with preexisting renal disease or compromised renal perfusion risk acute renal failure; leukopenia occurs rarely, is transient, and usually returns to normal during therapy; persistent leukopenia, granulocytopenia, or thrombocytopenia warrants further evaluation and may require discontinuation of drug

Drug Name	Ketoprofen (Orudis, Actron, Oruvail)
Description	For relief of mild to moderate pain and inflammation. Small dosages initially are indicated in small and elderly patients and in those with renal or liver disease. Doses over 75 mg do not increase therapeutic effects. Administer high doses with caution and closely observe patient for response.
Adult Dose	25-50 mg PO q6-8h prn; not to exceed 300 mg/d
Pediatric Dose	<3 months: Not established 3 months to 12 years: 0.1-1 mg/kg PO q6-8h >12 years: Administer as in adults
Contraindications	Documented hypersensitivity
Interactions	Coadministration with aspirin increases risk of inducing serious NSAID-related adverse effects; probenecid may increase concentrations and, possibly, toxicity of NSAIDs; may decrease effect of hydralazine, captopril, and beta-blockers; may decrease diuretic effects of furosemide and thiazides; may increase PT when taking anticoagulants (instruct patients to watch for signs of bleeding); may increase risk of methotrexate toxicity; phenytoin levels may be increased when administered concurrently
Pregnancy	B - Usually safe but benefits must outweigh the risks.
Precautions	Category D in third trimester of pregnancy; caution in congestive heart failure, hypertension, and decreased renal and hepatic function; caution in anticoagulation abnormalities or during anticoagulant therapy

Drug Category: Tricyclic antidepressants

A complex group of drugs that have central and peripheral anticholinergic effects, as well as sedative effects. They have central effects on pain transmission. They block the active re-uptake of norepinephrine and serotonin.

FOLLOW-UP

Section 8 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Further Outpatient Care

• Periodic physician visits should continue until the patient's symptoms have resolved or stabilized at maximum medical improvement (MMI).

Deterrence

• Deterrence and prevention focus on removing perpetuating factors. Using appropriate body mechanics, properly fitting furniture and workstations, and avoidance of prolonged static positioning all are important. Daily full ROM of all muscles is extremely helpful.

Prognosis

• Prognosis for resolution of MP is good if treatment is started in the acute phase and aggravating factors are eliminated. Treatment becomes more difficult as chronicity increases.

Patient Education

• Coverage of MP diagnosis and treatment in medical schools and residency programs should be expanded.
• For excellent patient education resources, visit eMedicine's Back, Ribs, Neck, and Head Center and Muscle Disorders Center. Also, see eMedicine's patient education articles Chronic Pain and Fibromyalgia.

MISCELLANEOUS

Section 9 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• Failure to administer adequate treatment is a potential pitfall. MP is a common finding in workers' compensation and auto accident cases. Patients frequently present for independent medical examinations and impairment ratings. Examinees frequently receive inadequate treatment. The examiner must determine whether the examinee is at MMI to give an impairment rating. Physicians must exclude a visceral cause of TrPs that could be masked temporarily by treatment.

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

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• Hameroff SR, Crago BR, Blitt CD, et al. Comparison of bupivacaine, etidocaine, and saline for trigger-point therapy. Anesth Analg. Oct 1981;60(10):752-5. [Medline].
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• Hsueh TC, Cheng PT, Kuan TS, Hong CZ. The immediate effectiveness of electrical nerve stimulation and electrical muscle stimulation on myofascial trigger points. Am J Phys Med Rehabil. Nov-Dec 1997;76(6):471-6. [Medline].
• Lang AM. Botulinum toxin therapy for myofascial pain disorders. Curr Pain Headache Rep. Oct 2002;6(5):355-60. [Medline].
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• Saggini R, Giamberardino MA, Gatteschi L, Vecchiet L. Myofascial pain syndrome of the peroneus longus: biomechanical approach. Clin J Pain. Mar 1996;12(1):30-7. [Medline].
• Simons DG, Travell JG, Simons L. Travell and Simons'. Myofascial Pain and Dysfunction:The Trigger Point Manual: The Lower Extremities. 1999.
• Simons DG. Review of enigmatic MTrPs as a common cause of enigmatic musculoskeletal pain and dysfunction. J Electromyogr Kinesiol. Feb 2004;14(1):95-107.
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Article Last Updated: Mar 22, 2006