Put simply, myofascial trigger points are painful, hyper-irritable areas in muscles that cause pain, stiffness, limited range of motion and sometimes other symptoms. They can refer pain to other parts of the body - sometimes very far from their original location. As a result they are often misdiagnosed.
Trigger points are always created in certain places in a muscle and always refer pain to the same areas. However, because there are hundreds of muscles in the body, there are hundreds of possible locations for trigger points. Also, trigger points in one muscle tend to create trigger points in other nearby muscles.
Myofascial trigger points are classified as either active or latent (inactive). Latent ones do not cause pain, but can still reduce range of motion. An active trigger point is easy to recognize by pressing on it, because it feels very painful. Often it is also palpable as a small "knot".
What Causes Trigger Points
Repetitive movements and prolonged use of the same muscles are common causes of trigger points. However, a sedentary lifestyle is also a risk factor. As a result pretty much any job can cause trigger points, whether it involves physical labour or prolonged sitting or standing. Poor posture promotes trigger points, but the reverse is also true.
A single strained movement can also cause trigger points, such as may happen in sports, falling or trying to prevent falling. Carrying or lifting heavy objects frequently promotes trigger points - which also goes for pregnancy. Surgery and dental operations are also common causes. Emotional stress often leads to muscle tension and thus trigger points. Cold temperatures often aggravate the problem.
Certain illnesses and metabolic conditions make one more prone to myofascial trigger points. These include anemia and some other nutritional deficiencies, viral infection, hypothyroidism, adrenal insufficiency and hypoglycemia. Genetic predisposition can be a factor for some people. Some medications like lithium and calcium channel blockers may also be to blame.
Chronic Pain from Trigger Points
Besides pain in the muscles, myofascial trigger points can cause joint pain, headaches (of all types) and other kinds of pain, such as eye pain, mouth pain, earache and pain in the genitals. The pain is often severe and does not respond well to painkillers. Especially NSAIDs and acetaminophen (paracetamol) tend to be useless.
The pain is frequently misdiagnosed as a serious condition, such as arthritis, bursitis, carpal tunnel syndrome, dental woes or degenerative spinal changes. Even when these conditions are present, trigger points often add to the pain. Trigger points may explain children's growing pains and some of the pain and balance problems associated with old age.
While myofascial pain is different from fibromyalgia, these conditions often coexist. Trigger points can cause the pain or contribute to it in interstitial cystitis and temporomandibular joint pain (TMJ/TMD).
Most physical injuries are also complicated by trigger points, which explains why such conditions as whiplash often persist for years, even when the original injury should have healed. Untreated, trigger points can cause problems for years or even decades.
Other Symptoms and Misdiagnosis
Myofascial trigger points also affect circulation and the function of the autonomous nervous system, which can lead to such symptoms as blurry vision, nasal congestion, restless legs syndrome, tinnitus, muscle weakness and atrophy, problems swallowing, urinary frequency and incontinence, intermittent claudication, numbness, dizziness, cold extremities and dyspnea (air hunger).
Trigger points in the torso can promote digestive symptoms like stomach ache, bloating, heartburn, diarrhea, constipation, nausea and even vomiting. Pelvic trigger points can be behind sexual dysfunction such as impotence and pain during and after intercourse, the latter in both sexes. They often contribute to dysmenorrhea (painful periods).
Many massage therapists and dentists know about trigger points, but physicians only rarely do. Because of this symptoms caused by trigger points are usually attributed to other conditions. This can lead to misdiagnosis of a serious condition such as appendicitis or a heart attack and/or even unnecessary surgery.
Treatment of Myofascial Trigger Points
Trigger points do not generally respond well to medication and normal stretching can even make them worse, but luckily they can be treated with e.g. self-applied massage at the trigger point.
References
Travell J, Simons D. Myofascial Pain and Dysfunction: The Trigger Point Manual. 1983.
Vázquez-Delgado E, Cascos-Romero J, Gay-Escoda C. Myofascial Pain Syndrome associated with Trigger Points: a literature review (I). Med Oral Patol Oral Cir Bucal. In press 2009.
Ettlin T, Schuster C, Stoffel R, et al. A distinct pattern of myofascial findings in patients after whiplash injury. Arch Phys Med Rehabil. 2008 Jul;89(7):1290-3.
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