Concept: Apropos Assessment

Concept: Apropos of All Muscles — Assessment

Source: Travell & Simons' Myofascial Pain and Dysfunction: The Trigger Point Manual, Vol. 1, 2nd Ed. Chapter 3: Apropos of All Muscles, pp. 94–178. This page covers the assessment framework applied universally to every muscle chapter in the Manual. Clinical examination follows the standard order: Look → Move → Feel.

See also: Concept:Apropos Treatment, Concept: Trigger Point Injection, Chapter 2: General Overview of Myofascial Trigger Points

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1. Referred Pain and Tenderness

The pattern of referred pain and tenderness is often the key to identifying which muscle(s) are responsible for a myofascial pain syndrome.

Patient's Pain History

The patient is rarely aware of a trigger point (TrP) in the muscle that causes the myofascial pain — pain evoked by lying on an infraspinatus TrP at night is perceived in the shoulder, not at the guilty TrP in the muscle overlying the scapula. However, when the patient stretches or loads the involved muscle, he or she is likely to feel discomfort in the regions of the taut band attachments.

Regardless of the mode of onset, pain referred from myofascial TrPs is characterised as steady, deep, and aching, rarely as burning. It is to be distinguished from the prickling pain and numbness associated with paraesthesias and dysaesthesias of peripheral nerve entrapment or nerve root irritation. Two skin muscles — platysma and palmaris longus — refer a needle-like prickling sensation superficially. Throbbing pain is more likely to be due to vascular disease or dysfunction. Occasionally, a myofascial TrP initiates sharp, lancinating, or lightning-like stabs of pain.

The patterns of pain referred from TrPs in a muscle are reproducible and predictable. Knowledge of these patterns is used to locate the muscles most likely to be causing the spontaneous pain.

Drawing the Pain Pattern

A precise pictorial representation of the patient's pain is a valuable aid for locating TrPs causing myofascial pain. The patient should delineate the pain on his or her body using one finger; then the practitioner can draw its pattern on a blank body form. The patient should then examine the drawing for accuracy and completeness. Body forms from Figures 3.2 (full figure, front and left side), 3.3 (right side and back), and 3.4 (head) are used for this purpose.

Recording conventions used throughout the Manual:

• The area that hurts most severely, and/or most frequently, is drawn in solid red.
• Regions that are sometimes painful, or less painful, are stippled; the lighter the stippling, the less painful the area.
• A black (or white) X identifies the common location of the TrP in that muscle.
• A circled X can be used to locate a TrP injection site.
• After treatment, black diagonal lines record areas that were sprayed and stretched.

The TrP may be located anywhere in the endplate zone(s) of the muscle. The location of the endplate zone(s) depends on the fibre arrangement in that muscle (see Chapter 2: General Overview of Myofascial Trigger Points, Section C).

Interpretation of Initial Pain Patterns

Ask: is the drawing a simple, one-muscle, myofascial TrP pain pattern? A composite of several such patterns superimposed? Or does it have a distribution that is foreign to TrP pain patterns, and therefore most likely of non-myofascial origin?

A referred pain pattern may be composite in two ways:

1. A total pattern may comprise overlapping patterns from different muscles, so that the extent of the pattern exceeds that of one muscle.
2. If TrPs in several muscles all refer pain to the same area (e.g., the shoulder), the area may be larger and more hyperaesthetic than if the symptoms came from only one muscle.

In general, referral at least partly in the peripheral direction is most common (85% of patterns). Half of all patterns (48%) refer only in the direction of the periphery. In addition, 20% of all patterns include both peripheral and central referral, and 17% of peripheral patterns include a strong local pattern. Just 10% of the patterns have only a local pattern and just 5% refer only in a central direction.

Practical implication: once it is established where the patient hurts, one is much more likely to find the TrP located toward the centre of the body from the referred pain than to find the TrP located peripherally to the pain complaint.

Interpretation of Pain Patterns on Return Visits

When the patient returns pain-free with complete restoration of full range of motion and the prior TrP sites are no longer abnormally tender, the treatment was successful. If the patient returns claiming "no improvement," an accurate record of the previous pain pattern becomes critical.

If careful comparison of a current "no improvement" pain pattern with the patient's previous visit shows a distinct improvement, and if some of the muscles previously treated no longer contain tender TrPs, this represents satisfactory progress. A pain distribution in the location of a previous pain may mean that a less active TrP has been "unmasked" by eliminating a more severe pain from a TrP in the same functional unit.

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2. Anatomy

By knowing all of a muscle's attachments, one can deduce the major actions of the muscle, where to find it for palpation, and the direction of its fibres. The anatomical drawings of each muscle in this volume present the muscle alone with its bony attachments. The bones to which the muscle attaches are stippled more darkly than other bones.

Terminology

The names of the muscles come from Nomina Anatomica. In this manual, the words "origin" and "insertion" are avoided except in instances where the relation is unambiguous, as with finger attachments. The term attachment helps one to keep an open mind and to think of muscle functions in realistic terms.

Unless stated otherwise, descriptions of muscle attachments refer to the person in the upright position, standing straight, face forward, with arms and forearms at the side with the forearm supinated (anatomical position). Therefore, above is equivalent to cephalad, superior, or proximal, and below is equivalent to caudad, inferior, or distal.

Fibre Arrangement

A description of the fibre arrangement in muscles is commonly overlooked in anatomy texts. All the fibres of any one muscle are of nearly equal length, but usually with staggered attachments at the ends; muscle fibres usually attach to aponeuroses or to bone in a parallelogram arrangement.

Muscles designed for force production (e.g., quadriceps, scalenes, gastrocnemius) have relatively short fibres (low fibre length/muscle length ratios). Muscles designed for velocity of movement (e.g., biceps, hamstrings, tibialis anterior) have high fibre length/muscle length ratios.

Muscles designed to produce force have endplate zones that tend to run the length of the muscle, whereas muscles designed for rapid movement have endplate zones that run relatively transverse to the muscle (depending on muscle structure), but always near the midpoint of the muscle fibres.

Supplemental References

Supplemental references for additional illustrations of each muscle's anatomy are listed at the end of Section 2 of each muscle chapter.

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3. Innervation

The spinal and peripheral nerves that usually supply each muscle are identified in this section. In many muscles, there is considerable individual variation; rarely do anatomists agree completely on the segmental innervation of a muscle.

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4. Function

Since the actions of a muscle that provide the functions for which it is used are so closely intertwined, these two issues are considered together under one heading in each muscle chapter.

Understanding the actions of muscles is valuable diagnostically and therapeutically:

• Diagnostically: an accurate description of the precise movement made by the patient at the time that the TrP was activated, together with a knowledge of which muscles are used to produce and to control that movement, helps to determine which muscles were likely to have been strained at the time.
• Therapeutically: a knowledge of the movements and activities that depend upon the muscles being treated is needed in order to explain proper body mechanics to the patient.

Four sources of information were used to summarise the actions of a muscle: (1) the actions listed in anatomy texts based on the attachments of the muscle; (2) the movements produced by stimulating the muscle electrically; (3) electromyographic studies that reported which movements or efforts generated motor action potentials in that muscle; and (4) the movements reported by patients that, when overloaded or repeated, produced TrPs in that muscle.

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5. Functional Unit

The functional unit to which a muscle belongs includes the muscle(s) that reinforce and counter its actions as well as the joint(s) which the muscle crosses. The interdependence of these structures functionally is reflected in the organisation and neural connections of the sensorimotor cortex.

The functional unit is emphasised because the presence of an active TrP in one muscle of the unit increases the likelihood that other muscles of the unit will also develop TrPs. Dysfunction (weakness and shortening) of the affected muscle tends to overload other muscles of that functional unit. When inactivating TrPs in a muscle, one must be concerned about TrPs that may develop secondarily in muscles that are interdependent.

The physiological definition of a myotatic unit (the term used in the previous edition) includes the synergists, which help the prime mover (agonist), and the antagonists, because these muscles are linked by interacting reflex pathways. The term functional unit in this edition also includes muscles that do not necessarily share common reflexes, but which have close functional relationships — for example, muscles that extend the line of pull of the affected muscle during total body movements (e.g., the external abdominal oblique extends the line of pull of the serratus anterior muscle).

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6. Symptoms

With thorough knowledge of individual myofascial pain syndromes and of TrP referred pain patterns, one can often, with a careful history, not only identify the diagnosis of myofascial pain but also determine which muscles are most likely causing the pain.

History

Travell emphasised the importance of taking a thorough and thoughtful history in patients with chronic musculoskeletal pain.

Preliminary Review of Records. Before the first visit, the patient is requested to submit: a chronology of life events, a chronology of medical events, and a complete list of current and recent medications including nutritional supplements.

Chronology of life events should give dates and places of residence, education, marriages, children living (age and where they live), sports activities, travel, and employment.

Chronology of medical events should include illnesses, infections, accidents (fractures, falls, etc.), surgical procedures, dental procedures, pregnancies and miscarriages, allergies (tests and hyposensitizations), and vaccinations.

Medications list should include all medications currently being taken, including vitamin and mineral supplements. The patient is asked to bring a bottle of every medication so that the actual dosage can be established.

Diet — Questions regarding what foods the patient avoids may be as informative as those regarding what foods they eat. Myofascial TrPs are aggravated by high histamine levels and active allergies. The quality of the diet is determined not only by what the patient eats but by how this food is prepared.

Sleep — If patients report that they "sleep poorly," further questioning is in order. What position do they sleep in? Do they have "restless legs" (folic acid deficiency)? Body warmth is important for myofascial pain patients; when the muscles become cool at night, they contract to generate heat, and this tension can activate latent TrPs.

Work situation — A careful history of precisely what the patient ordinarily does at work (or at home) is fundamentally important. Many times, if the patient experiences intermittent pain, it is helpful for the patient to keep a written record of any onset of pain throughout the day and to relate it to activities at the time.

Timing of Pain

Myofascial TrPs may cause constant pain, intermittent pain, or no pain complaint. Patients in constant pain caused by TrPs are usually unaware of activities that aggravate the pain. Most patients with active TrPs experience intermittent pain that is characteristically aggravated by specific movements and may be alleviated at least temporarily by a certain position.

Latent TrPs give no primary pain clues and must be identified by postural changes, muscle dysfunction, and physical examination.

The onset of pain following activation of a TrP due to muscle overload can be delayed as long as 12 to 20 hours. Abrupt onset — the patient remembers clearly the first date of the pain and can describe the exact event. Gradual onset — is usually due to chronic overload of muscles; may also appear during or after a period of viral infection, visceral disease, or psychogenic stress.

Myofascial TrP pain is characteristically aggravated by:

1. Strenuous use of the muscle, especially in the shortened position.
2. Passively stretching the muscle.
3. Pressure on the TrP.
4. Placing the involved muscle in a shortened position for a prolonged period.
5. Sustained or repeated contraction of the involved muscle.
6. Cold, damp weather, viral infections, and periods of marked nervous tension.
7. Exposure to a cold draft, especially when the muscle is fatigued.

Myofascial TrP pain is decreased by:

1. A short period of rest.
2. Slow, steady passive stretching of the involved muscles, particularly when the patient is seated under a warm shower or in a warm bath.
3. When moist heat is applied over the TrP.
4. Short periods of light activity with movement (not by isometric contraction).
5. By specific myofascial therapy.

Limited Range of Motion

This is rarely the chief complaint, but it is a fundamental characteristic of TrPs that is readily identified by the pain that develops as the muscle approaches full stretch range of motion. Limitation of motion and increased stiffness are worse in the morning and recur after periods of overactivity or immobility during the day.

Although the range of motion of a muscle with TrPs does not test passively as being restricted at the shortened end of the range, such a muscle is intolerant of being left relaxed in the shortened position for a period of time, and quickly develops a cramp-like pain on voluntary contraction in the shortened position.

Weakness

Frequently, patients are aware of weakness of certain movements — pouring milk from a carton, turning a doorknob, or carrying groceries in one arm. The muscle learns to limit the force of its contraction below the pain threshold of the central and attachment TrPs. Weakness may be a reflection of inhibition referred from a TrP in another muscle.

The clinician must determine why the muscle is weak and the type of weakness. Myofascial TrPs contributing to or causing the weakness may be in the same muscle and/or in functionally related muscles.

Other Non-pain Symptoms

Patients may report excessive lacrimation, nasal secretion, pilomotor activity, and occasionally changes in their sweat patterns, but TrP activity is rarely seriously considered as the source of these symptoms. An involved limb may feel cold as compared with the opposite one due to reflex vasoconstriction. The examiner should be alert for symptoms of postural dizziness, spatial disorientation, and disturbed weight perception.

Depression

A major, well-recognised contributor to depression is chronic pain. Depression may lower the pain threshold, intensify pain, and impair the response to specific myofascial therapy. Patients who have suffered myofascial pain for months or years are likely to also have developed secondary depression and sleep disturbances, and to have restricted their activity and exercise. Folic acid or pyridoxine deficiency and low thyroid function are potent contributors to depression, and may also increase neuromuscular irritability and TrP pain.

Depression must be recognised — if untreated or under-treated, it blocks recovery from myofascial syndromes. It is diagnosed by a variety of clues: insomnia, anorexia and weight loss, impotence or decreased libido, blurred vision, sad mood, thoughts of suicide or death, strong feelings of guilt, inability to concentrate, poor memory, indecisiveness, mumbled speech, and a negative reaction to suggestion.

Sleep Disturbances

A careful history identifies the seriousness and nature of sleep disturbance. Depressed patients tend to fall asleep readily but awaken in the night and have trouble sleeping again. Some patients are awakened by their myofascial pain, others by noises.

Prognosis

Acute myofascial pain due to TrPs caused by a clearly identifiable strain of one muscle is, as a rule, able to be fully relieved and normal function restored. The longer the period between the acute onset of pain and the beginning of treatment, the greater the number of treatments that will be required over a longer period of time.

Patients who have had a stable pattern of referred TrP pain for months or longer, without extension to other muscles, are likely to respond better to treatment than patients with progressively more severe symptoms.

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7. Activation and Perpetuation of Trigger Points

Acute events that precipitate a sudden onset of symptoms and the chronic stresses that are likely to produce a gradual onset of TrP symptoms are both considered here.

Sudden Onset

The mechanical stresses that tend to activate myofascial TrPs acutely include: wrenching movement, automobile accidents, falls, fractures (including chip fractures), joint sprains, dislocations, or a direct blow to the muscle. Acute onset may also be associated with an episode of excessive or unusual exercise.

Intramuscular injection of medicinal substances given inadvertently at the site of a latent TrP may activate it. Latent TrPs in a fatigued muscle, especially in the calf or neck and shoulders, may be activated by direct cooling of the overlying skin, as by a cold draft from air conditioning or an open car window.

Gradual Onset

Locating the cause of active TrPs that developed gradually due to chronic overload can be difficult, but it is important because the chronic strain, if continued, perpetuates and may intensify the TrPs. Typical causes of sustained postural overload are poor work habits, such as a slouched posture or a keyboard operator lifting the shoulders to reach an elevated keyboard.

Synergistic muscles that are overloaded by substituting for an involved muscle, or are in sustained contraction to protectively splint an involved muscle, are themselves likely to develop secondary TrPs.

A muscle that is immobilised in the shortened position for prolonged periods tends to develop active TrPs. Nerve compression, such as in radiculopathy caused by a ruptured intervertebral disc, favours the development of TrPs in the muscles supplied by the compressed nerve root (postdisc syndrome). The "nervous tension" associated with emotional stress or psychological tension can induce TrPs.

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8. Patient Examination: LOOK

This section considers the examination of the patient for dysfunctions and phenomena that are characteristically produced by TrPs. It assumes the clinician has taken or reviewed the patient's complete medical history and that the patient has received a general medical examination that paid special attention to neurological function in order to distinguish symptoms of neurological origin from those of myofascial TrP origin.

This patient examination section distinguishes between primary TrP effects that are the direct result of the TrP pathophysiology and secondary TrP effects that are induced by the TrP activity.

Patient Mobility and Posture

The patient's spontaneous posture and movements should be observed while he or she walks, sits, or removes articles of clothing. People with painfully active TrPs tend to move slowly and protectively. They avoid, or explore gingerly, movements that might painfully stretch or load muscles with TrPs, and they may be compensating for muscles that are weak because the muscles are reflexly inhibited by TrPs in the same or other muscles.

Key observations:

• Does the patient use arms and hands bilaterally in their full range of motion?
• Does the body, rather than only the head, turn when the patient looks around?
• In the sitting position, is the spine crooked and one shoulder lower than the other?
• Is the face symmetrical?
• Does the patient perform spontaneous stretching movements for relief; if so, what muscles are being stretched?

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8. Patient Examination: MOVE

Neuromuscular Functions

This heading includes examination for restricted stretch range of motion, weakness, distorted weight perception, and weak deep-tendon reflexes.

Restriction of stretch is the primary effect of the increased muscle tension and shortening caused by the TrP mechanism. The restriction is augmented by pain arising secondarily from sensitised nociceptors in central TrPs and at attachment TrPs.

Restriction of Movement. A muscle containing active TrPs is functionally shortened and somewhat weakened. Attempts to passively extend the muscle to its fully stretched length cause pain at less than normal range. The characteristic painfulness to passive stretch in one direction and to active contraction in the other was reported specifically for 10 muscles by Macdonald. Any movement, especially a quick manoeuvre, that markedly increases tension in the muscle, either stretching or contracting it, can cause pain.

To identify active or latent TrPs that may limit range of motion and thus influence dysfunction, Boeve suggested the examiner should: (1) identify limited range of motion by performing specific range of motion testing for a particular segment; (2) take up slack to the point of tension before changing the position; (3) ask the patient where he or she feels the tension or where it hurts; (4) search (palpate) there for a taut band and TrP.

Screening tests for normal range of head and neck muscles — the seated patient should be able to:

• Place the chin firmly on the chest, looking straight up at the ceiling.
• Turn the head at least 90° so that the chin points to the acromion.
• Place the ear close to the shoulder without shrugging.

For shoulder-girdle muscles — the Mouth Wrap-around Test (Fig. 18.2): the hand should cover at least half of the mouth with the arm behind the head. The Hand-to-shoulder-blade Test (Fig. 22.3): the fingertips on the non-dominant side normally reach to the spine of the contralateral scapula.

Weakness. It is important to think beyond the obvious weak function of a muscle or muscle group and not to assume that all it needs is strengthening exercises. The clinician must determine why it is weak and the type of weakness. Static testing, as performed in conventional testing of muscle strength, attempts to produce a voluntary contraction of just the muscle being tested. Dynamic testing monitors muscle activity while the subject is performing functionally meaningful tasks that have been learned and that require muscle coordination.

Sudden premature cessation of effort by the patient during static testing may be due to painful loading of distant stabilising muscles, to painful loading of the muscle being tested, or to a sudden inhibition of effort just short of painful loading that has been "learned" by the muscle being tested.

Distorted Weight Perception. Testing for the disturbance of weight appreciation caused by sternocleidomastoid TrPs is described in Chapter 7, Section 8.

Weak Deep-tendon Reflexes. Myofascial TrPs in a muscle can reduce the briskness of the deep-tendon reflex response elicited by tapping the tendon of that muscle. A weak or even absent ankle jerk due to active TrPs in the soleus muscle demonstrates this — within minutes following inactivation of the TrPs, the previously weak ankle jerk equals that of the normal side.

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8. Patient Examination: FEEL

Referred Tenderness

Referred pain and referred tenderness are closely related neurophysiologically. Most of the animal studies that are interpreted as relevant to the neurophysiological mechanisms responsible for referred pain are actually studies of referred tenderness.

Trigger point referred tenderness must be distinguished from enthesopathy. TrP referred tenderness is distributed diffusely throughout the involved area and is not well localised. Enthesopathy presents a circumscribed tenderness specifically in the regions of muscle attachment. When enthesopathy is caused by central TrPs, the tenderness is localised where the taut bands (of the TrPs) attach.

Cutaneous and Subcutaneous Signs

Dermographia. Dermographia has been strongly identified with the fibrositis syndrome. We find that dermographia in the skin overlying muscles with active myofascial TrPs occurs most often over muscles of the back of the neck, shoulders and torso, and less frequently over limb muscles. Regular use of an antihistamine may be indicated.

Panniculosis. In panniculosis, one finds a broad, flat thickening of the subcutaneous tissue with an increased consistency that feels coarsely granular. It is not associated with inflammation. Panniculosis is usually identified by hypersensitivity of the skin and the resistance of the subcutaneous tissue to "skin rolling." Skin rolling is accomplished by picking up a fold of skin and subcutaneous tissue between the fingers and the thumb, and moving the hand across the surface by rolling the fold forward.

Compression Test

When a patient presents with myofascial pain felt only during movement (not at rest), manually compressing the muscle responsible for that movement (while the movement is being performed) sometimes prevents the referred pain. For example, when sternocleidomastoid TrPs cause pain on swallowing, firmly squeezing a roll of the skin overlying the sternocleidomastoid can block the pain and render swallowing temporarily pain-free.

The Compression Test can be used to demonstrate to the patient the myofascial TrP origin of the pain without imposing additional pain.

Joint Play

Loss of joint play is a common cause of pain-producing joint dysfunction that commonly interacts strongly with myofascial TrPs. This joint dysfunction is considered an important component of osteopathic somatic dysfunction by Jacobs and Falls, who state that "The restoration of joint play appears to be the basis for the success of synovial joint mobilisation using direct or indirect action treatment techniques in osteopathic manipulation." Joint play examination and treatment are frequently simple and full recovery can often be greatly expedited by examining and treating the patients promptly for restricted joint play, especially if inactivating the TrPs does not fully restore normal range of motion.

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9. Trigger Point Examination

Limitations of stretch range of motion and records of referred pain patterns help to identify which muscles to examine for active TrPs; palpation and observation of TrP phenomena confirm which muscles are responsible for the myofascial pain.

While the muscles are being examined for TrPs, the patient should be comfortable and warm. The muscle must be relaxed; otherwise, the distinction between tense bands and adjacent slack muscle fibres is diminished or lost. Before the examiner attempts to palpate a muscle for TrPs, the examining digits must have the fingernails trimmed very short. An appreciable length of fingernail not only causes the patient unnecessary (sometimes severe) pain, but the skin pain caused by long fingernails is readily misinterpreted as TrP tenderness.

Clinical rule: palpate for TrPs only in those muscles that can be treated during the same visit.

Diagnostic Criteria

The most reliable diagnostic criterion of TrPs on examination of the muscle is the presence of exquisite tenderness at a nodule in a palpable taut band. If, in addition, the patient recognises pain that is elicited by digital pressure on (or needle penetration of) the TrP as his or her clinical pain complaint, the TrP is clinically active, not just latent.

Palpable Tender Nodule and Taut Band

The optimal elongation of a muscle for palpating taut bands (which is usually the first step in palpating the TrP) is at a position that is slightly longer than the position of ease. In this case, the uninvolved muscle fibres are still slack, but the taut band fibres are placed under additional tension by lengthening the muscle to the point of a perceptible increase in resistance to movement. This is also the optimal tension for eliciting LTRs and for making LTRs most visible.

A taut band feels like a palpable cord of tense muscle fibres among the normally pliable fibres. The examiner should palpate along the taut band to locate the nodule that corresponds to a circumscribed slightly enlarged region of decreased compliance. This nodular region is also the location of maximum tenderness (the TrP).

Three kinds of palpation can be used:

Flat palpation — refers to the use of a fingertip that employs the mobility of the subcutaneous tissue to slide the patient's skin across the muscle fibres. The skin is pushed to one side of the area to be palpated and the finger slides across the fibres to be examined, allowing the skin to bunch on the other side. Any ropy structure (taut band) within the muscle is felt as it rolls under the finger. Used for relatively superficial muscles accessible from one side only (e.g., extensor digitorum communis).

Pincer palpation — performed by grasping the belly of the muscle between the thumb and fingers and pressing the fibres between them with a back-and-forth rolling motion to locate taut bands. When a taut band is identified, it is explored along its length to locate the nodule and spot of maximum tenderness, which identifies a TrP. Used when opposite site sides of the muscle are accessible and the belly can be grasped between the digits (e.g., sternocleidomastoid, pectoralis major, latissimus dorsi, biceps brachii).

Deep palpation — used when intervening tissue makes the muscle inaccessible to flat or pincer palpation. The examiner must use the fingertip over an area of skin that overlies the motor-point region or attachment region of the muscle suspected of harbouring TrPs. Localised tenderness that is elicited only when the finger pressure is directed in one specific direction is compatible with the diagnosis of either a central or attachment TrP if pressure elicits pain recognised by the patient as his or her pain complaint. Used for deep muscles with considerable tissue between them and the skin (e.g., quadratus lumborum, gluteus minimus, piriformis).

Referred Pain

The referred patterns characteristic of myofascial TrPs are not unique to just the TrP itself. Patterns that are similar or nearly identical may be elicited from other structures including zygapophyseal joints, muscle tissue two centimetres removed from the TrP but still in the taut band, and attachments of the muscle that exhibit enthesopathy.

Compression of either an active or latent central TrP can reproduce the typical pattern of referred pain of a given muscle. However, eliciting referred pain that is not recognised by the patient but conforms to the expected pain pattern for that muscle does not identify a latent TrP unambiguously, though it can be very helpful diagnostically.

The spontaneous referred pain pattern reported by the patient is a very helpful indicator of where to start looking for TrPs.

Sufficient pressure on an active TrP almost always elicits at least withdrawal, wincing, or vocalisation by the patient — the jump sign. The extreme sensitivity to applied pressure that elicits the jump sign is not by itself considered a sufficient diagnostic criterion of a TrP.

Local Twitch Response (LTR)

The LTR is a transient contraction of essentially those muscle fibres in the tense band that are associated with a TrP. It may be seen as a twitch or dimpling of the skin near the terminal attachment of the fibres, or palpated through the skin with the examining hand.

The LTR is readily elicited and perceived in the muscles that permit pincer palpation (deltoid, gluteus maximus, vastus medialis, finger and wrist extensors). Muscles like the subscapularis or multifidi are unlikely to exhibit LTRs by palpation, but can be elicited by needle contact with the TrP.

Most muscles exhibit a vigorous LTR only if they harbour active TrPs, but the middle finger extensor, in most adults, contains a latent TrP that responds with a readily visible LTR.

Gerwin et al. in their interrater reliability study noted that the one criterion which distinguished an active TrP from a latent TrP was the patient's recognition of his or her pain complaint when the active TrP was compressed.

The LTR is a strongly confirmatory diagnostic finding when elicited manually and is especially valuable when elicited during the needling of TrPs. However, for most clinicians, an LTR is generally not a satisfactory criterion for making the diagnosis of myofascial pain caused by TrPs.

Central and Attachment Trigger Points

It is now necessary to distinguish central TrPs located in the endplate zone of a muscle from attachment TrPs that occur in a region of attachment of the muscle.

Table 3.2: Comparisons Between Central TrPs and Attachment TrPs

Finding	Most Likely Cause
Central TrPs
In motor endplate zone	Dysfunctional endplates
Nodule	Contraction knots
Local and referred pain	Nociceptors sensitised by local energy crisis
Taut band beyond nodule	Contraction knot tension
Attachment TrPs
In attachment zone	Taut band tension
Palpable induration	Inflammatory reaction
Local and referred pain	Nociceptors sensitised by persistent taut band tension
Taut band at attachment TrP	Contraction knots in central TrP

The primary central TrP abnormality is associated with individual dysfunctional endplates in the endplate zone (or motor point). This dysfunction produces a local energy crisis that results in sensitisation of local nociceptors. This dysfunction can produce contraction knots which then produce a nodule and a taut band of tense muscle fibres.

The attachment TrPs result from the sustained increased tension of these muscle fibres at the attachment point. This sustained tension can produce enthesopathy with swelling and tenderness where the muscle fibres attach to an aponeurosis, tendon, or bone.

Key and Satellite Trigger Points

A Key TrP is one that is responsible for the activity of one or more satellite trigger points. Clinically, a key TrP becomes apparent when inactivating it also inactivates its satellite TrPs without direct treatment of the satellite TrPs themselves.

A Satellite TrP is one that is activated as a result of being in the pain reference zone or the zone of increased motor activity of a key TrP.

Table 3.3: Key Trigger Points and Their Satellite Trigger Points (Hong CZ, 1994 — asterisked entries)

Key Trigger Point	Satellite Trigger Points
Sternocleidomastoid	Temporalis*, Masseter*, Lateral Pterygoid*, Digastric, Orbicularis Oculi*, Frontalis*
Upper Trapezius	Temporalis*, Masseter, Splenius, Semispinalis Capitis, Levator Scapulae*, Rhomboid Minor*, Occipitalis*
Lower Trapezius	Upper Trapezius
Scaleni	Serratus Posterior Superior*, Pectoralis Major* and Minor*, Deltoid, Extensor Digitorum Communis*, Extensor Carpi Radialis and Ulnaris, Long Head Triceps Brachii*
Infraspinatus	Anterior Deltoid*, Biceps Brachii
Latissimus Dorsi	Long Head Triceps Brachii*, Flexor Carpi Ulnaris

*Asterisked satellite TrPs are those specifically observed and reported by Hong CZ, 1994.

Key and satellite TrPs are related TrPs. The role as to which muscle harbours the key TrP may sometimes reverse. Knowledge of these relationships is used to examine for Key TrPs that might be overlooked when the patient complains chiefly of symptoms produced by the satellite TrP.

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10. Entrapment

When a nerve passes between taut bands in a muscle, or when a nerve lies between a taut TrP band and bone, the unrelenting pressure exerted on the nerve can produce neurapraxia (loss of nerve conduction) but only in the region of compression. Occasionally, there is EMG evidence of some neurotomesis (axonal loss) in addition to neurapraxia.

The patient with one of these entrapments is likely to present with two kinds of symptoms: aching pain referred from TrPs in the involved muscle, and the nerve compression effects of numbness and tingling, hypoaesthesia, and sometimes hyperaesthesia.

Signs and symptoms of partial neurapraxia may sometimes be relieved within minutes after inactivation of the responsible myofascial TrPs, which immediately relaxes the taut bands.

Table 3.4: Nerve Entrapments by Myofascial Taut Bands (Vol. 1 muscles)

Entrapped Nerve	Muscle	Vol. 1 Chapter
Accessory	Sternocleidomastoid	7
Brachial Plexus, lower trunk	Pectoralis Minor	43
Brachial Plexus	Anterior and Middle Scalenes	20
Digital	Interossei, hand	40
Greater Occipital	Semispinalis Capitis	16
Intercostal	Intercostal	45
Musculocutaneous	Coracobrachialis	29
Radial	Triceps Brachii	32
Radial, sensory	Brachialis	31
Radial, superficial sensory	Extensor Carpi Radialis Brevis	34
Radial, deep	Supinator	36
Serratus Anterior, motor nerve	Middle Scalene	20
Spinal, posterior primary rami	Thoracolumbar Paraspinal	48
Supraorbital	Frontalis	14
Ulnar	Flexor Digitorum, deep, superficial	38
Ulnar	Flexor Carpi Ulnaris	38
Ulnar, deep (motor) branch	Opponens Digiti Minimi	40

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11. Differential Diagnosis

This section identifies other diagnoses that are commonly applied to patients when the pain is caused by TrPs. It also considers the problem of misdiagnosing one of those other conditions as TrPs and not treating it appropriately.

TrPs are frequently given other diagnoses: patients frequently arrive with a long list of diagnostic procedures and diagnoses, none of which satisfactorily explained the cause of, or relieved, the patient's pain. Table 2.5 (in Chapter 2: General Overview of Myofascial Trigger Points) lists examples of 24 common conditions that were misdiagnosed when TrPs were actually the cause.

Conditions closely related to myofascial TrPs that are commonly both present include fibromyalgia, articular dysfunctions, temporomandibular dysfunctions, occupational myalgia, nonmyofascial TrPs, and the posttraumatic hyperirritability syndrome.

The relation between acupuncture and myofascial TrPs is considered in Chapter 2, Section B.

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See Also

• Concept:Apropos Treatment
• Concept: Trigger Point Injection
• Chapter 2: General Overview of Myofascial Trigger Points
• Travell & Simons Trigger Point Manual — Index

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References

This page is based entirely on: Simons DG, Travell JG, Simons LS. Myofascial Pain and Dysfunction: The Trigger Point Manual. Volume 1: Upper Half of Body. 2nd ed. Baltimore: Williams & Wilkins; 1999. Chapter 3: Apropos of All Muscles, pp. 94–178.