A myofascial trigger point (TrP) is a hyperirritable localized area located on a palpable taut muscle band or skeletal muscular fascia. It can potentially refer the pain or other symptoms to different body parts. To put it simply, it refers to as a tight and painful muscle knot.
It can be divided into active and latent trigger points.
(a) Active TrPs may produce pain even when they are not compressed. They may also be associated with other symptoms such as weakness, "pins and needles" sensation, temperature changes, or referred pain.
(b) Latent TrPs present with pain occurs only on the application of external pressure.
How A Trigger Point Form?
The most prominent theory for TrP genesis is called the energy crisis hypothesis. ATP molecules provide the energy necessary to run the functions of a cell, including muscle contraction. If the mechanism is deprived of ATP molecules to initiate the active process of relaxation, the muscle contraction will be maintained, resulting in the formation of a TrP.
The underlying cause of the lack of ATP molecules is ischemia (restriction in blood supply) due to the muscle tightness itself.
- When a muscle contracts at approximately 30% to 50% of its maximum and persists for long hours, it is sufficient to constrict the blood vessels within it, restricting the blood flow.
- When the muscle loses its blood supply, this resulting in loss of nutrients including those required to generate ATP molecules.
- A deficiency of ATP molecules cause muscle stays contracted, its contraction then continues to cut off the blood supply and this initiates a vicious cycle known as contraction – ischemia cycle.
- Besides, the metabolic waste products are accumulated in the tissues when the blood flow is restricted.
- These waste products are acidic which can irritate the muscle tissue, and resulting in the symptoms like pain.
- This may lead to pain – spasm – pain cycle. The pain triggers more muscle contraction, which then creates the buildup of waste products and produce pain.
References:
1. Leesa K. Huguenin. 2004. Myofascial Trigger Points: The Current Evidence. Physical Therapy in Sport 5: 2–12.
2. Joseph E. Muscolino. 2009. The Muscle and Bone Palpation Manual with Trigger Points, Referral Patterns and Stretching. Mosby Elsevier.
3. M. Saleet Jafr. 2014. Mechanisms of Myofascial Pain. International Scholarly Research Notices 1-16.