Myofascial Trigger Points Then and Now: A Historical and Scientific Perspective

Myofascial pain syndrome (MPS) affects millions of people and represents one of the most common reasons patients seek care from primary care physicians and pain clinics. Despite its prevalence, the condition has been plagued by inconsistent terminology, controversial diagnostic criteria, and limited acceptance within mainstream medicine. At the heart of this clinical puzzle lies the myofascial trigger point (MTrP)—a hard, palpable nodule in a taut band of skeletal muscle that may be spontaneously painful (active) or painful only when pressed (latent). For decades, clinicians and researchers have debated whether MTrPs are truly necessary for diagnosing MPS, or whether they represent merely one finding among many in a complex pain syndrome.

This paper traces the evolution of thinking about MTrPs from early 19th-century clinical observations through contemporary scientific investigations, highlighting how new technologies and research methods are reshaping understanding of this common but enigmatic condition.

The authors conducted a comprehensive narrative review of historical and contemporary literature on MTrPs and MPS. They examined original writings from pioneering clinicians including Guillaume de Baillous (1538-1616), who was among the first to describe muscle pain disorders in detail; Balfour, who in 1816 associated "thickenings" and "nodular tumors" with muscle pain; and Froriep, who coined the term "muskelshwiele" (muscle callouses) in 1843. The review extensively covers the groundbreaking work of Janet Travell and David Simons, whose two-volume "Myofascial Pain and Dysfunction: The Trigger Point Manual" remains the most influential clinical resource in the field. The authors then synthesized modern scientific investigations across multiple domains: biochemical analyses using in vivo microdialysis to measure substances in the local muscle milieu; advanced imaging techniques including ultrasound, elastography, and shear wave elastography to characterize MTrP structure and mechanical properties; neurophysiological studies examining spontaneous electrical activity and central nervous system processing; and clinical studies evaluating various treatment approaches.

They also examined alternative theoretical frameworks, including Stecco's fascial hypothesis involving hyaluronic acid accumulation and Quinter and Cohen's peripheral nerve sensitization model.

The historical review reveals that understanding of MTrPs evolved through multiple conceptual frameworks: from Gowers' discredited "fibrositis" theory (inflammation of fibrous tissue) to Schade's "myogeloses" (high viscosity muscle colloids), to Kellgren's demonstration of referred pain patterns through hypertonic saline injections, and finally to Travell and Simons' comprehensive MTrP-centered model. Contemporary research has yielded several important objective findings about MTrPs. Biochemical studies by Shah and colleagues demonstrated elevated levels of substance P, calcitonin gene-related peptide (CGRP), bradykinin, serotonin, norepinephrine, and other sensitizing substances in the local milieu of active MTrPs. Imaging studies by Sikdar and colleagues using ultrasound and elastography revealed that MTrPs appear as hypoechoic regions with increased mechanical stiffness, and that active MTrPs are associated with substantial heterogeneity in the surrounding muscle milieu rather than isolated nodular lesions.

Shear wave elastography showed affected muscle to be stiffer compared to normal muscle. Neurophysiological studies confirmed spontaneous electrical activity at MTrP loci, originally attributed to dysfunctional muscle spindles but later identified as increased miniature endplate potentials and excessive acetylcholine release. The Cinderella hypothesis provides a plausible mechanism for MTrP development, explaining how smaller type I muscle fibers, continuously activated during low-level exertions, become metabolically overloaded and susceptible to calcium dysregulation. The authors also found that central sensitization plays a significant role in MPS, with limbic system structures (anterior cingulate gyrus, insula, amygdala) activated in patients with MPS, and that latent MTrPs may contribute to central sensitization through sub-threshold nociceptive signaling.

Treatment research showed that dry needling caused immediate analgesia in nearly 87% of cases in Lewit's study, with over 31% experiencing permanent relief, and that elicitation of a local twitch response produces more immediate and long-lasting pain relief than no elicitation. However, the authors noted that the number of randomized, placebo-controlled trials remains few, with most having small sample sizes.

This comprehensive review demonstrates that MPS and MTrPs are transitioning from a purely clinical, palpation-based construct to a condition with emerging objective biomarkers and measurable pathophysiological features. For patients, this means that the validity of their pain condition is gaining scientific support beyond subjective reports—imaging and biochemical findings are beginning to corroborate what patients have long described. For clinicians, the review emphasizes that while palpation remains the practical gold standard for diagnosis, awareness of the broader neuro-muscular dysfunction (including central sensitization and fascial changes) should inform comprehensive treatment approaches. The finding that MTrPs exist within a heterogeneous "neighborhood" of muscle and fascial abnormalities suggests that treatments targeting only the discrete nodule may be insufficient; rather, addressing the surrounding tissue environment and contributing factors (posture, overuse, sleep, mood) may be necessary for sustained relief.

The historical perspective also cautions against premature acceptance of any single theoretical model—multiple plausible mechanisms likely contribute to MPS in different patients, and the field must remain open to evolving understanding. The review identifies critical unanswered questions that should guide future research, including whether MTrP resolution is required for clinical improvement, how tender nodules progress to full MPS, and what roles anti-inflammatory versus pro-inflammatory substances play in the local biochemical milieu. Ultimately, the paper argues that proper treatment of MPS requires identifying and targeting the specific mechanisms and perpetuating factors operating in each individual patient, rather than applying uniform protocols based on incomplete understanding.