Myofascial trigger point is a cluster of electrically active loci, each of which is associated with a contraction knot and a dysfunctional motor endplate in skeletal muscle.
Spontaneous Electrical Activity, or SEA, can lead to collecting adjacent muscle fibres within a spasm. (Hong C-Z, Torigoe Y. Electrophysiological characteristics of localized twitch responses in responsive taut bands of rabbit skeletal muscle fibers. J Musculoskel Pain 1994;2(2): 17-43).
Other processes, such as the biochemistry of the area of pathology can also result in progression of spasm beyond the original source. “We have confirmed that biochemicals associated with pain, inflammation, and intercellular signaling are elevated in the vicinity of active MTrP’s. Furthermore, subjects with active MTrP’s in the upper trapezius have elevated levels of these biochemicals in a remote, unaffected muscle, suggesting that these conditions are not limited to localized areas of active MTrP’s.” (Biochemicals Associated With Pain and Inflammation are Elevated in Sites Near to and Remote From Active Myofascial Trigger Points.(Author abstract)(Report).Jay P. Shah, Jerome V. Danoff, Mehul J. Desai, Sagar Parikh, Lynn Y. Nakamura, Terry M. Phillips and Lynn H. Gerber. Archives of Physical Medicine and Rehabilitation 89.1 (Jan 2008): p16(8)).
This can address the progression from acute to chronic pain syndromes. This also highlights why early treatment can be advantageous. Early work on tenderness and motor points described the beginning of an important new medical subject, “neuropathic pain”. Electromyographic (EMG) evidence of neuropathy in the nerves, tender muscles, increased insertional activity, polyphasic action potentials, prolonged motor action potentials, etc., demonstrated this. Pain can be of muscular origin as well. This can be due to damaged muscle fibers leading to spasm. ( Dr. Chan Gunn: “Tenderness and Motor Points” (Journal of Bones and Joint Surgery,Vol. 58A, No.6 Sept. 1976)).
Muscular injury can occur when soft tissues are exposed to single or recurrent episodes of biomechanical overloading. Muscular pain is often attributed to a myofascial pain disorder, a condition originally described by Drs Janet Travell ,David Simons & Lois Simons (1999). Myofascial Pain and Dysfunction: The Trigger Point Manual (2 vol. set, 2nd Ed.). USA: Lippincott Williams & Williams.
Muscles with activity or injury-related pain are usually abnormally shortened with increased tone and tension. In addition, myofascial pain disorders can be characterized by the presence of tender, firm nodules called trigger pointsDr. Chan Gunn: “Tenderness and Motor Points” (Journal of Bones and Joint Surgery,Vol. 58A, No.6 Sept. 1976)
Research has demonstrated that muscular contraction knots are the histopathologic characteristics of trigger points. Chan Gunn’s work supported this notion, and suggested a similar histologic structure of the shortened muscles with palpable sensitive or painful bands, or points.
The clinical definition describes a hyper-irritable spot in skeletal muscle that is associated with a hypersensitive palpable nodule in a taut band. The spot is painful on compression and gives rise to characteristic referred pain, referred tenderness, motor dysfunction and autonomic phenomena.