What are Trigger Points, and how do we treat them?

Trigger Points Definition

Trigger points are points of hyperirritability.

A German named Max Langer discovered that spots could appear in the muscles sensitive and that the tissue of these points was more rigid than the surrounding ones.

These points were named in 1948 by Dr. Janet Travell, a White House physician, during the Kennedy presidency.

Dr. Travell called “Trigger Points” and she developed a treatment method using saline injections for their suppression.

She later discovered that it was possible to deactivate the T.P. using only direct pressure on them.

T.P. is a tiny zone (diameter between 0.5 and 1 centimeter) highly irritable located inside the muscle, which appears rigid on palpitation and produces pain, limitation of stretch amplitude, and weakness without atrophy or neurological deficit.

Sometimes it can give rise to autonomous (vegetative) phenomena and distortion of proprioceptive sensitivity.

Trigger points’ characteristics:

  1. They generate pain.
  2. They are bundles of hyperirritable myofibrils arranged anarchically as if knotted, inside the taut band of the muscle.
  3. They decrease the elasticity of the muscle and its fascia where they are present.
  4. They can be found on top of each other, located in overlapping muscles (at the time of treatment should be released sequentially, one below another one, starting with the most superficial, most active, and most recent).

Trigger Point Pathophysiology

From the histopathological point of view, it is recognized as a key element of the Trigger Point, the presence of muscle knots, which corresponds to a segment of muscle fiber subjected to a strong contracture of its sarcomeres.

The muscle fibers that contain muscle knots form a taut band. The area or region of muscle fibers that contains muscle knots constitutes the palpable painful muscle nodule.

Only some fibers of the affected muscle present this microscopic alteration. At the level of contraction nodes, sarcomeres present a strong contraction (shorter and wider) differing markedly from the sarcomeres of the normal fibers of the same muscle. At the end of the fibers with contraction knots sarcomeres are elongated and slimmed down.

From the pathophysiological point of view, Trigger Points are intimately associated with neuromuscular junctions that are in a dysfunctional state. 

The neuromuscular junction is the structure that links the terminal nerve of a motor neuron with a muscle fiber. It contains the synapse, the neurotransmitter that is the

acetylcholine. The functional alteration occurs in fibers of the muscle causing segmental contraction (shortening) trigger point area and compensatory passive elongation towards

both ends. The fibers in this state can be palpated (tense band).

The dysfunction of the neuromuscular junction would be related, according to a hypothesis to a local energy crisis, caused due to neurovegetative dysregulation. They develop within the reference zone of the original active TP. They do not cause pain during normal activities. They are only painful palpation. 

They are activated by cold, heat, atmospheric pressure changes, and repetitive damage.

Types of Trigger Points

In normal clinical practice, we can find three types of myofascial Trigger Points:

  1. ACTIVE TRIGGER POINTS: They are painful without stimulation. Always sensitive, the patient feels like a constant pain point. The pain increases by palpating the muscle, pressing it, mobilizing it, and by stretching.
  2. SECONDARY TRIGGER POINTS: They usually develop in response to existing overload in the area when the agonist and synergist muscles of the affected muscle try to compensate or help this damaged muscle.
  3. LATENT OR SATELLITE TRIGGER POINTS: They develop within the reference zone of the original active Trigger Point. They do not cause pain during normal activities. They are only painful on palpation. 

Most Common Locations of Trigger Points

The distribution and topographic frequency of the Trigger Points are not uniform.

They are preferentially located in the muscles of the head, neck, and shoulder girdle such as the temporalis muscle, masseter muscle, trapezius muscle, supraspinatus muscle, rhomboids muscle, sternocleidomastoid muscle.

In the lumbar region, those most frequently affected by Trigger Points are the erectus of the rachis and the quadratus lumborum.

Curiously the muscles most predisposed to the appearance of Trigger Points are those that also function as muscles accessory respiratory muscles.

Referred pain also appears more frequently when Trigger Points are located in the areas of the neck and shoulders.

Other common muscles where Trigger Points are located are in the leg and hip muscles. 

The most common causes of Trigger Points

The reason why a Trigger Point is formed in a certain moment and in a certain muscle, is still unknown, despite the many hypotheses issued.

However, multiple pathogenic factors have been found to trigger, predisposing, or favoring Trigger Points, such as:

  1. Sleep disturbances.
  2. General stress.
  3. Muscular stress: Due to excessive physical exercise of the muscles involved.
  4. Repetitive microtrauma: They are small traumas, of very low intensity, that in isolation do not cause damage, but when constantly repeated can give rise to muscle knots.
  5. Acute musculoskeletal trauma: It can affect muscles, tendons, ligaments, or bursae (e.g. “whiplash cervical”).
  6. Sudden cooling of the body or partial body areas: For example, staying in front of a fan or air conditioning.
  7. Exhaustion or generalized fatigue: For example in the Chronic Fatigue Syndrome.
  8. Vertebral pathology and discopathies: Degenerative alterations.
  9. Joint inflammations.
  10. Nerve root injury.
  11. Partial inactivity of a body segment: For example cervical collar or cast.
  12. Nutrient deficiencies.
  13. Obesity or Overweight.
  14. Endocrine diseases: For example hormonal changes and menopause.
  15. Emotional disorders: For example depression, anxiety, emotional stress.

Diagnostic Criteria of Trigger Points

The diagnosis of Trigger Points is based mainly on clinical assessment through the meticulous manual exploration of the Trigger  Points and identification of the zones of reference.

So Trigger Points are identified by palpation, first superficial and later deep. This requires a certain practice, skill, good touch, and great palpatory anatomy.

The T.P. It is palpated as a painful or hyper-painful nodule, hard, very small, with a size ranging between 5 and 10 millimeters in diameter and with a consistency like “crunchy rice”.

The temperature of the affected muscle will be increased by a very localized area in cases of acute dysfunction. Will be decreased in chronic cases (ischemia), which indicates changes in fibrotic tissue and vascular ecstasy with decreased metabolism.

Local edema can be perceived, which is a sign of

waterlogging of the tissues (lymphatic failure). In chronic cases, the initial edema is gradually replaced by fibrotic (connective tissue) changes.

There are no laboratory or radiological objective data that can be correlated with the clinical findings.

However, some theses and works have attempted to demonstrate that electromyography and thermography as tests complementary can provide data in favor of the diagnosis.

Various biochemical abnormalities have been indicated, including:

  1. Reduced contents of adenosine triphosphate (ATP).
  2. Reduced contents of adenosine diphosphate (ADP).
  3. Reduced content of phosphocreatin (CP).
  4. Reduced content of Glycogen.
  5. High levels of adenosine monophosphate (AMP).
  6. High levels of Creatine.
  7. Abnormally low subcutaneous oxygen tension in the Trigger Points has suggested an increase in metabolism. 

Furthermore, the accumulation of H2O and fat, mucopolysaccharides, platelets, and mast cells (degranulated) have been shown in nodules fibrotic. Platelets and mast cells release serotonin and histamine, which stimulate the peripherals nerve, contributing in this way to a state of hypersensitivity.

Capillary lysis, myofibrillar lysis, and endothelial cell changes have also been presented.

Although all these abnormalities have been detected in the Trigger Points biopsy is not diagnostic.

Diagnostic Methods of Trigger Points

To diagnose and quantify trigger Points is necessary to resort to methods that are not always very objective, since the pain when perceived subjectively, has not been able to be quantified with accuracy, despite multiple attempts, and must use measurement systems based on questionnaires and scales.

The most important are the following:

  1. Identification by careful palpation.
  2.  Diagnostic dry injection: It consists of sticking a needle (sterile) at the trigger point. This causes a local spasmodic response (jerking).
  3. The administration of a muscle relaxant two hours before the exploration: It will allow us the most accurate detection of the active Trigger Points since the pain of the secondary and satellite TPs is temporarily suppressed.
  4. Pressure with the algometer: This instrument allows us to measure the pressure pain threshold over muscles that have TP.
  5. Thermography: Thermographically, TP manifests itself with a small area that has a temperature between 0.6 and 1º C more than the tissue surrounding it or its contralateral area. If the thermography is performed in the area of referred pain, an average reduction of 0.6º C. during the compression of the TP is observed.
  6. Electromyography.
  7. Numerical pain scales: (Borg pain scale perceived). The patient rates their pain from 0 to 10. With 0 being the absence of pain and 10 being unbearable pain. Bit reliable.
  8. Percutaneous electroneurography.
  9. Simple Verbal Scale: It is normally used to measure the intensity of the pain. The patient is asked to describe his pain based on the following scale: “I don’t feel any pain,” “mild pain,” “moderate pain,” “significant pain,” and “The pain cannot be greater.” They depend on the personality of the patient and her environment. They are unreliable.
  10. Visual analog scales (VAS): It consists of a line of 10 centimeters, at the left end of which appears the description “absent pain” and on the far right “pain maximum imaginable.” The patient is asked to mark on the scale the point that would represent the level of pain that presents. The distance in centimeters between the end left and the marked point is dominated by the score of the pain. It is more reliable than simple verbal scales.
  11. McGill University Quiz: It is reliable and valid to measure pain as a multidimensional experience since that evaluates the sensitive, effective, and intensity aspects of the pain.
  12. Local anesthetic blocks: When anesthetizing a TP the pain disappears in that point and in its reference area.
  13. Pain diagrams: initially described by Dr. Janet Travell and Simons.
  14. Acupuncture point diagrams: According to some authors many TPs correspond to acupuncture points.

Clinical Characteristic of Trigger Point Pain Syndrome

Summarizing the clinical characteristics of the trigger point pain syndrome or myofascial pain syndrome we can identify these findings in the muscle area affected:

  1. Muscle with limitation of movement.
  2. Muscle weakness: The maximum force of contraction is decreased, but atrophy is not seen, nor is neurological deficit.
  3. Protective muscle spasm.
  4. Contracted and shortened muscle.
  5.  “Jump sign” on palpation.
  6. The muscles neighboring the injured one also appear tense to palpation.

Trigger Points in Sport

In recent years it has been noted that numerous sports injuries, muscle pain, and athletic disorders called in sports jargon “contractures” or “muscle knots”, are nothing more than myofascial pain with the formation of trigger points.

If you carefully explore the muscles involved, it will be observed that there is no such overload globally, it is not the entire muscle that hurts.

We will find that the shortened and weak muscle has a tight band on the inside of which a TP appears. These TPs are located in muscles overstressed by sports practice, which increase your vulnerability to damage, with greater and rapid exhaustion, and an increase in tension and stiffness, which are direct results of the training.

These muscle microtraumas from exercise, favor the accumulation of waste products that originate in the muscle (particularly lactic acid and potassium ions), reduce drastically the oxygenation capacity of the same, and reduce the blood flow.

All this implies a shortening of the muscle fiber that causes tension in the muscle, pain as a response of the nerve to the compression carried out by the spasmodic muscle, and so on until pain becomes chronic.

All these conditions increase muscle vulnerability and the period of muscle recovery, activating a vicious circle predisposing the athlete to get a sports injury.

The development of PGs in specific muscle areas of the athlete is conditioned, commonly by a wide variety of factors, among these we must highlight the:

  1. Genetics.
  2. Metabolism.
  3. Athlete’s habits.
  4. Specificity of each sport.
  5. The stress of the muscles used: It determines the specific place of  TP formation. Many athletes always develop these TPs in the same area of the same muscles, which are the ones that most intervene in the practice of their sport.

Many factors can perpetuate Trigger Points in athletes, the most frequent being the following:

  1. Forced and repetitive postures.
  2. Vicious postures (antifunctional and antianatomical).
  3. Dismetries of the lower limbs.
  4. Pelvic laxity with abdominal atrophy.
  5. Lumbar hyperlordosis with psoas tension.
  6. Nutritive, metabolic, endocrine, and hormonal factors.
  7. Emotional factors.
  8. Anatomical problems.
  9. Stressful chemicals: caffeine, nicotine, alcohol, and theine.
  10. That the muscle does not recover its normal resting position with stretching exercises (Travell, Simons).
  11. That Trigger Points are not treated.
  12. If the muscle that houses the PG is forced to work, it will perpetuate the PG and other secondary ones will appear (Starlanyil and Copeland).

Clinically, the athlete manifests dull and heavy pain.

The muscle feels tense, hypertonic, and contracted.

The muscle is exhausted quickly and significantly decreases sports performance.

Treatments of Trigger Points

There are different types of treatments and rehabilitation techniques that can be utilized to treat trigger points.

Depending on the status and entity of the Trigger points, we can perform different rehabilitation techniques to ease trigger points such as:

  1. Sports Massage.
  2. Deep Tissue Massage.
  3. Myofascial Release technique.
  4. Instrument Soft Tissue Mobilization (IASTM) (Trigger points with fibrotic tissue).
  5. Diacutaneous Fribrolysis (Trigger points with fibrotic tissue and adhesions).

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