Myofascial pain affects up to 95% of people with chronic pain disorders and is usually a result of myofascial trigger points in muscles, tendons or fascia. Myofascial pain syndrome is diagnosed by the presence of trigger points, which are hyper-sensitive tender spots within tight bands of skeletal muscles. Active trigger points are painful independently whereas latent trigger points are only painful when pressed, but no spontaneously. Stiffness and loss of range of motion can be seen along with referred pain into other locations, such as the arms, legs or torso.
There is some debate about the actual cause of trigger points, but the most accepted theory currently is that a series of events within the muscle fibers causes a sustained contraction of the muscle. This leads to decreased blood flow and increased metabolic demand which leads to a decrease in oxygen and release of chemicals locally that produce pain. Another theory is that there is increased firing at the neuromuscular junction causing sustained contractions.
Several factors have been suggested that may lead to developing and maintaining trigger points. These include poor posture, work or sports activities causing excessive strain on a particular muscle, tendon, or ligament, lack of sleep, and lack of exercise. Postural habits include sitting with the legs crossed, sitting leaned to the side or leg length discrepancies. Sleeping consistently on one side with the top leg crossed over can also lead to shortening of muscles in the low back on one side causing pain. Ergonomic factors at work can also lead to trigger points and should be evaluated in cases of chronic myofascial pain syndrome.
Deficiencies of vitamin D, B12 or iron have been linked to chronic musculoskeletal pain. Vitamins C, B1 and B6 deficiency also have been associated with diffuse muscle pain. Hypothyroidism is known to cause myofascial pain, as do infections of Lyme, Hepatitis C or enteroviruses.
When evaluating patients with myofascial pain, I rely on history a great deal. If the pain is more localized, then mechanical or structural causes are more likely. If the symptoms are more generalized, then we consider more system causes such as nutritional, metabolic or hormonal disorders.
On examination, I look for abnormal posture, shoulder or pelvic tilt, increased curvature of the low back, hamstring or hip flexor tightness, or leg length discrepancies. Any of these things can place excess strain on muscles, tendons, ligaments and fascia. When palpating the trigger points I look for whether the pain response is localized or referred to other areas.
Appropriate treatment of myofascial pain syndrome requires a comprehensive rehabilitation approach. Treating the trigger points without addressing the underlying problem will not provide any long-term benefit. By working to fix the cause, such as muscle imbalance or poor posture, it will be less likely that the trigger points return.
I like to start with conservative measures such as a stretching program consisting of slightly contracting the affected the affected muscle followed by relaxation and stretching. Myofascial release in physical therapy is also a great option since muscle imbalances can be addressed with a strengthening program once the trigger points are released. Deep tissue massage and osteopathic manipulation can relieve the pain temporarily, but do not usually address the underlying cause. Muscle relaxers can also be used short-term for pain relief, but again do not fix the underlying problem.
Trigger point injections (TPI) have about the best evidence for effectively treating trigger points and relieving symptoms associated with myofascial pain. I usually perform a TPI if the patient does not get good results from physical therapy or medication. The most important thing is finding the correct active trigger point that is the source of pain. A small needle is inserted into the trigger point and an anesthetic agent is injected. The needle breaks up the trigger point and the anesthetic decreases the post-injection soreness.