Also called myofascial trigger point, the trigger point is a hyperirritable spot in skeletal muscle. Trigger points are associated with palpable nodules in taut bands of muscle fibers. It is believed that palpable nodules are small contraction knots and a common cause of pain.
Myofascial pain syndrome is a common painful muscle disorder characterized by myofascial trigger points.
This is different from fibromyalgia syndrome, which involves multiple tender points, though the two pain syndromes may occur together.
Myofascial trigger points are a major cause of pain and dysfunction. They produce pain locally and in a referred pattern.
Pressing the point may cause local tenderness, referred pain, or local twitch response.
The trigger points frequently cause pain that frequently radiates from these points of local tenderness to broader areas, sometimes quite far away from these points. In spite of being accepted them as a different entity, enough diagnostic criteria and cause of there origin is not known
The term was coined in 1942 by Dr. Janet Travell.
A typical trigger point is said to have the following characteristics
- Pain related to a discrete, irritable point in skeletal muscle or fascia, not caused by acute local trauma, inflammation, degeneration, neoplasm or infection.
- The painful point can be felt as a tumor or band in the muscle, and a twitch response/tenderness/referred pain can be elicited on stimulation of the trigger point.
- Palpation of the lesion reproduces the patient’s complaint of pain
Not all may have these classical features though.
The exact mechanism is unknown.
The most recent proposed mechanism says that trigger points are muscle spindles, made over-active by adrenalin stimulation. These very short muscle fibers (< 1 cm in length) called intrafusal muscle fibers are activated by adrenalin via the sympathetic nervous system.
An event of muscular overload causes a prolonged release of calcium from the sarcoplasmic reticulum (storage unit for the muscle cell) which results in sticking cells leading to a contracture with compression of capillaries and results in an increased local energy demand and local ischemia (loss of blood circulation) to the area. This energy crisis causes the release of chemicals that augment pain.
Types of Trigger Points
Active & Latent
An active is one that actively refers pain either locally or to another location
A latent trigger point is one that exists but does not yet refer pain actively. It may do so when pressure or strain is applied to the myoskeletal structure containing the trigger point.
Key & Satellites
A key trigger point is one that has a pain referral pattern along a nerve pathway that activates a latent trigger point on the pathway or creates it.
A satellite trigger point is one which is activated by a key trigger point.
Successfully treating the key trigger point often will resolve the satellite and return it from being active to latent, or completely treating it too.
Primary & Secondary
A trigger point in many cases will biomechanically activate a secondary one in another structure. The original one is called the primary.
Treating the primary does not treat the secondary trigger point.
What Activates A Trigger Point?
- Acute or chronic muscle overload
- Activation by other trigger points
- Psychological distress
- Direct trauma to the region
- Radiculopathy ( Pain due to compression /irritation of nerve root
Where Can Trigger points Appear?
- Joint capsule
- Scar tissue.
Trigger points are diagnosed by clinical history and examination that includes manual palpation. Pain patterns and a taut band or hard nodule guide to the diagnosis. A twitch response can be felt in the muscle by running finger perpendicular to the muscle’s direction.
Locating a Trigger Point
When we palpate muscles for trigger points, a palpable taut band or cord of tense muscle fibers approximately 1-4 mm in diameter is encountered. Palpation along this band would reveal a point of maximum tenderness which is the area identified as the trigger point. A firm pressure on the point would reveal the referred pain pattern.
Palpation of an active trigger point often elicits a local twitch response.
Also called jump sign, It refers to a jump or involuntary reflex–like the movement of the patient when the trigger point is pressed.
The jump is disproportionate to the amount of pressure exerted and is reproducible.
It is thought to correspond to the degree of irritability of the trigger point.
Another kind of twitch response is local muscle twitch when the trigger point is rolled under the fingers or a needle is inserted into the trigger area. This occurs as a notable contraction of the muscle fibers in the taut band for about up to 1 second.
Pressing on an affected muscle can often refer pain.
There are many choices for treatment of trigger point.
- Manual massage
- Mechanical vibration
- Pulsed ultrasound
- Ischemic compression
- Dry Needling
- Local anesthetics/steroid injection
- Low-Level Laser Therapy
- Stretching techniques that invoke reciprocal inhibition
Quite a lot of trigger points respond to physical therapy, especially in the early stages of trigger point formation.
For chronic ones, dry needling and trigger point injection is an effective treatment.
In dry needling, a filament needle [acupuncture needle] is inserted into the skin and muscle aiming at trigger points band. It can be done at the superficial or deep tissue level.
After trigger points have been deactivated, muscle and fascial stretching should be done.
Dry needling is thought to be effective by
- Stimulation of a local twitch response which reduces the concentration of painful substances in the chemical environment near myofascial trigger points.
- Muscle regeneration
- The release of intracellular potassium that may depolarize and disrupt nerve conduction.
Some studies have reported dry needling to be only slightly better than placebo.
Trigger Point Injections
[Read on the procedure of trigger point injection]
Trigger point injections are an effective treatment modality for inactivating trigger points and providing prompt relief of symptoms from myofascial pain syndrome.
The injection includes administration of local anesthetic like lidocaine or procaine. Use of saline has been recommended for patients allergic to anesthetic agents.
Following mechanisms have been thought to cause the effect
- Disruption of abnormal muscle fibers or nerve endings breaking the sensorimotor loop
- The release of intracellular potassium causing depolarization and disruption of nerve conduction due to needling
- Dilution of nerve-sensitizing substances which reduces irritability and inactivate any neural feedback mechanisms.
- Interruption feedback mechanisms between the trigger point and the central nervous system by anesthetic
- Focal necrosis may destroy the trigger point.
After the procedure, the muscle is stretched.
Activity modification and exercises are included in the treatment regime after an injection.
Ask the patient to rest the affected areas for one to two days after the injections.
As long as injection soreness is there, strenuous activities should be avoided but range of motion exercises are encouraged.
In the long run, patient needs to recognize and avoid the pain-provoking activities and muscle stressing movements. Learning to use muscles well and with proper alignment is key to long-lasting relief.
After inactivation of trigger points and resolution of rest pain, a carefully graded exercise program is introduced.
This includes stretching exercise of the involved muscles, improved conditioning and increased strength reduces the likelihood of developing trigger points.
- Alvarez DJ, Rockwell PG. Trigger points: diagnosis and management. Am Fam Physician. 2002 Feb 15. 65(4):653-60.
- Ge HY, Nie H, Madeleine P, Danneskiold-Samsøe B, Graven-Nielsen T, Arendt-Nielsen L. Contribution of the local and referred pain from active myofascial trigger points in fibromyalgia syndrome. Pain. 2009 Dec 15. 147(1-3):233-40.
- Lucas N, Macaskill P, Irwig L, Moran R, Bogduk N. Reliability of physical examination for diagnosis of myofascial trigger points: a systematic review of the literature. Clin J Pain. 2009 Jan. 25(1):80-9.