Physical Medicine and Rehabilitation for Myofascial Pain

Myofascial pain (MP) is a common, painful disorder that is 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 there are approximately 400 muscles in the body. MP is responsible for many cases of chronic musculoskeletal pain and the diagnosis is commonly missed.[1]

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.[2]

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 TrP has been inactivated. Latent TrPs cause stiffness and limitation of ROM but no pain. Frequently, they are found in asymptomatic individuals.

Although MP and fibromyalgia have some overlapping features, they are separate entities; fibromyalgia is a widespread pain problem, not a regional condition caused by specific TrPs.

A taut band in a muscle may be necessary as a precursor to the development of a trigger point (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 myofascial pain is not well understood. 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, as well as LTRs, may be mediated through the spinal cord after stimulation of a sensitive locus.[3, 4]

In a study by Alonso-Blanco et al, a connection was found in women between the number of active myofascial TrPs and the intensity of the spontaneous pain and widespread mechanical hypersensitivity; nociceptive inputs from these myofascial TrPs may be linked to central sensitization.[5]

Work by Shah et al using a microdialysis catheter demonstrated an increase in biochemicals associated with pain, including protons (a more acidic environment), inflammatory mediators, neuropeptides, cytokines, and catecholamines in the tissue around active trigger points. Uninvolved control points showed lower concentrations of these compounds, but the levels were still higher than in subjects without myofascial pain syndrome.[6]

Frequency

United States

Myofascial pain (MP) is extremely common, and almost everyone develops a trigger point (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

Myofascial pain (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 the incidence of myofascial pain have been described in the literature.

Sex

Myofascial pain is distributed equally between men and women.[7]

Age

Myofascial trigger points (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 are individuals who exercise vigorously on a daily basis.

Patients with myofascial pain 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. An acute onset may occur after a specific event or trauma (eg, moving quickly in an awkward position), while chronic pain may result from poor posture or overuse.[8] Patients may note disturbed sleep. Persons with cervical[9] and periscapular myofascial pain may have difficulty finding a comfortable sleeping position. They may or may not be aware of muscle weakness in the affected muscles and may have a tendency to drop things.

A skilled examiner can provide accurate diagnosis of myofascial pain (MP). Unfortunately, most medical school and residency training programs do not adequately cover this common condition.[10] Locating trigger points (TrPs) is the most important part of the physical examination. TrPs tend to occur in characteristic locations in individual muscles. The book Travell and Simons' Myofascial Pain and Dysfunction: The Trigger Point Manual is considered the criterion standard reference on locating and treating TrPs.[3, 11, 12]

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 an LTR. The jump sign simply means that the patient jumps from pain or discomfort in the area that has been palpated. Apply a consistent amount of pressure to the area, because applying too much pressure can elicit pain in nearly all individuals. A pressure algometer (ie, pressure threshold meter) or palpatometer can be used to standardize the amount of pressure applied.[13]

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 a 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 an LTR may be noted in active TrPs, as well as in latent ones. 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 a latent TrP causes referred pain in a characteristic area for each muscle, a phenomenon described in the above-mentioned TrP manual. 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 an LTR

• Imaging of an LTR induced by needle penetration of a tender nodule

• Pain or altered sensation on compression of a tender nodule, in the distribution expected from a TrP in that muscle

• Electromyographic demonstration of spontaneous electrical activity (SEA) that is characteristic of active loci in the tender nodule of a taut band

• Lowered skin resistance to electrical current - This has been found over active TrPs when compared with surrounding tissue and may be useful in localizing TrPs. Skin resistance normalizes after the treatment of TrPs.

Many factors may contribute to the development of myofascial pain (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 cause MP.

Assumption of a static position for a prolonged period or conversely, performing repetitive movements, has been implicated in the condition, particularly in a cold environment.

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.

No specific lab tests confirm a diagnosis of myofascial pain (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 (CBC), 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.

Infrared or liquid crystal thermography can show increased blood flow, which is sometimes noted at trigger points. Other imaging studies are useful only to rule out other sources of pain generation. However, a study by Kumbhare et al indicated that ultrasonographic muscle texture analysis can be used to differentiate between healthy trapezius muscles and those affected by myofascial pain.[14]

Needle electromyography (EMG) examination of trigger points (TrPs) in 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. Ultrasonography has been used to visualize the LTR elicited by needle penetration.

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

Trigger point (TrP) injections sometimes are performed with bupivacaine, etidocaine, lidocaine, saline, or sterile water.[15, 16, 17, 18] Dry needling is occasionally performed, without the injection of any substance.[19, 20]

TrP injection results are better if an LTR can be elicited. Ultrasonographic guidance can be helpful for recognition of LTR in deeper muscles, but is not helpful in finding TrPs.[21]

Botulinum toxin (BOTOX®) shows promise as a substance that can provide long-lasting relief.[22, 23, 24, 25, 26] Its mechanism of action may be related to the blocking of acetylcholine release at the neuromuscular junction of the dysfunctional motor endplates.

A retrospective study by Avendaño-Coy et al indicated that in combination with physical therapy, intramuscular injections with botulinum toxin type A (BoNT-A) are effective against myofascial pain (MP) syndrome. The study, which involved the records of 301 patients with persistent MP syndrome, found that at 6 months, positive results were achieved with this treatment combination in 58.1% of patients, including 82.9% of those with primary MP syndrome and 54.9% of those with secondary MP syndrome. The effectiveness of therapy in the latter group was influenced by the disorders associated with secondary MP syndrome.[27]

A report by Affaitati et al indicated that a topical anesthetic patch can also relieve myofascial pain, without the discomfort that can result from TrP injections.[28] Patients in the study were separated into groups of 20, one of which was treated for 4 days with a lidocaine patch applied to each patient's trigger point (with patients receiving a total daily dose of 350 mg). The second group received a placebo patch, and the third group was treated with injections of 0.5% bupivacaine hydrochloride.

In members of the lidocaine patch and bupivacaine injection groups, the investigators found significant decreases and increases in, respectively, subjective symptoms and pain thresholds. Although the effects at muscle TrPs and target areas were more pronounced in the injected patients, the lidocaine patients experienced less therapy-related discomfort. Subjective symptoms and pain thresholds did not improve in the placebo group.

Physical Therapy

Physical therapy for patients with myofascial pain 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 in decreasing pain, allowing the patient to participate in an active exercise program.[29]

Corrections of leg-length discrepancies with a heel lift or the 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:

• Phonophoresis[30, 31]

• Massage and exercise[32]

• Stretching

• Electrical muscle stimulation (EMS) using interferential current (IFC), functional electrical stimulation/electrical nerve stimulation (FES/ENS), or high-frequency transcutaneous electrical nerve stimulation (TENS)[33, 34]

• Ultrasonography[32, 35, 36]

• EMG biofeedback[37]

• Low-energy laser[38]

A literature review by Ahmed et al suggested that electroacupuncture is more effective than transcutaneous electrical nerve stimulation (TENS) at reducing MP. The study also indicated that treatment duration may affect the success of electrical stimulation in MP but that the frequency and number of treatments may not.[39]

A study by Chan et al indicated that a program of self-massage and home exercise aids in the treatment of MP dysfunction syndrome (MPDS). The study included 31 control patients, who received six sessions of heat therapy and TENS, and 32 patients who received the same treatment, as well as undergoing a program of self-massage and home exercise. The latter group showed greater improvement than the other patients, including significant increases in the pressure pain threshold of trigger points (TrPs) and significant improvements in the neck disability index and the patient-specific functional scales.[40]

A retrospective study by Halder et al indicated that treatment combining onabotulinumtoxinA (BOTOX®) injections with myofascial release physical therapy under anesthesia is effective against myofascial pelvic pain in women. Average pelvic pain scores in the study decreased from 6.4 to 3.7, while the number of trigger points were reduced. Moreover, patient self-reported pelvic pain was characterized as improved by 58% of patients. Patients with chronic bowel disorders were most likely to report no pain improvement, while patients who had undergone past treatment with an incontinence sling were most likely to report pain reduction.[41]

Occupational Therapy

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

Trigger points (TrPs) can result from noxious stimuli, such as a herniated disc. Inquire about such precipitating factors in the patient's environment.

The 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, neural or vascular injury, or penetration of an underlying organ (which could lead to pneumothorax).

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

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• Acupuncture may be helpful.[42, 43, 44]

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

The Society of Obstetricians and Gynaecologists of Canada

Consensus guidelines on the management of chronic pelvic pain (CPP) from  state the following with regard to myofascial CPP[45] :

• Health-care providers need greater awareness of myofascial dysfunction as a source of CPP and of the available treatments
• Management of CPP due to myofascial dysfunction should include patient engagement in a home stretching and exercise program

Muscle relaxant medications[46] and nonsteroidal anti-inflammatory drugs (NSAIDs) can at times be a useful adjunct to active, exercise-based treatment for myofascial pain, but they are helpful only rarely on their own. Medications such as low-dose amitriptyline may help to improve the patient's sleep cycle. Botulinum toxin type A injected into trigger points can reduce muscular contractions through the inhibition of acetylcholine release at the neuromuscular junction and appears to have an antinociceptive effect.[22, 23, 24, 25] Current research suggests that peripheral sensitization is blocked, which indirectly reduces central sensitization.[29] Transdermal lidocaine patches can be helpful.[47]

Class Summary

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

Ibuprofen (Motrin, Ibuprin, Advil)

DOC for patients with mild to moderate pain. Ibuprofen inhibits inflammatory reactions and pain by decreasing prostaglandin synthesis.

Naproxen (Naprosyn, Anaprox, Naprelan)

For relief of mild to moderate pain. Naproxen inhibits inflammatory reactions and pain by reducing the activity of cyclooxygenase, which results in decreased prostaglandin synthesis.

Ketoprofen (Orudis, Actron, Oruvail)

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 the therapeutic effects. Administer high doses with caution, and closely observe the patient for a response.

Class Summary

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

Amitriptyline (Elavil)

Analgesic for certain chronic and neuropathic pain.

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• For patients with myofascial pain, periodic physician visits should continue until the individual's symptoms have resolved or have stabilized at maximum medical improvement (MMI).

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• The deterrence and prevention of myofascial pain focus on removing perpetuating factors. Using appropriate body mechanics, avoiding prolonged static positioning, and properly fitting furniture and workstations all are important. Full ROM of all muscles on a daily basis is extremely helpful.

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

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• Coverage of myofascial pain diagnosis and treatment in medical schools and residency programs should be expanded.[10]

• For excellent patient education resources, see eMedicineHealth's patient education articles Chronic Pain and Fibromyalgia.