ProbableMechanismsofNeedlingTherapiesforMyofascialPainControl

Myofascial pain syndrome (MPS) is one of the most common musculoskeletal pain conditions, characterized by muscle pain caused by myofascial trigger points (MTrPs). These hyperirritable spots in palpable taut bands of skeletal muscle can cause local pain, referred pain, and local twitch responses. Needling therapies—including MTrP injection, dry needling, and acupuncture—have been used for decades to treat MPS, often providing immediate pain relief. However, the exact mechanisms behind this pain relief have remained unclear.

This review addresses the need to understand how needling therapies work at physiological and neurological levels, which is essential for optimizing treatment approaches and improving patient outcomes.

The authors conducted a comprehensive narrative review of existing literature on needling therapies for myofascial pain control. They examined multiple dimensions of the topic: (1) the pathophysiology of MTrPs, including the integrated hypothesis of excessive acetylcholine release, sarcomere shortening, and sensitizing substances; (2) the historical and technical aspects of various needling therapies including MTrP injection, dry needling, superficial dry needling, and acupuncture; (3) the mechanisms of acupuncture analgesia involving endogenous opiates, serotoninergic pathways, anti-inflammatory mechanisms, and the cholinergic anti-inflammatory pathway; (4) clinical trials comparing different needling approaches; (5) basic research on biochemical changes at MTrP sites; and (6) animal studies investigating remote effects of needling. The review synthesized findings from electrophysiological, neurophysiological, and biochemical studies to build a comprehensive picture of how needling therapies may work.

The review identified several key mechanisms that likely contribute to pain relief from needling therapies. The analgesic effect of acupuncture appears to involve multiple systems: endogenous opiates including β-endorphin, enkephalin, endomorphin, and dynorphin; serotoninergic descending pain inhibitory pathways from the nucleus raphe magnus; and anti-inflammatory mechanisms involving reduced substance P, CGRP, and other inflammatory mediators. For dry needling specifically, the local twitch response (LTR) appears crucial—eliciting LTR during needling suppresses the irritability of sensitive loci in MTrPs. Biochemical studies by Shah and colleagues found that active MTrPs had elevated concentrations of substance P, CGRP, bradykinin, serotonin, norepinephrine, TNF-α, and IL-1β compared to latent MTrPs and normal muscle tissue, and these levels decreased after LTR.

Regarding remote needling effects, the review found that needling distant points can reduce MTrP irritability. Animal studies by Hsieh and colleagues demonstrated that dry needling of a distal MTrP could reduce irritability of a proximal MTrP, and that this remote effect requires intact afferent nerves and normal spinal cord segments corresponding to the innervation of the affected muscle. The neural pathway appears to be mediated via spinal reflex mechanisms. Clinical studies showed that acupuncture at trigger points was more effective than sham or non-trigger point acupuncture for chronic neck pain, and that distal acupuncture points could improve range of motion more than local points in some cases.

The correlation between acupoints and MTrPs was found to be substantial—Dorsher's study found 92% anatomic correspondence, 79.5% clinical correspondence, and 76% meridian-referred pain correspondence between trigger points and acupoints, suggesting these traditions may represent similar clinical phenomena despite different theoretical frameworks.

This review suggests that needling therapies for myofascial pain work through multiple complementary mechanisms rather than a single pathway. For patients, this means that different needling approaches—whether direct dry needling of trigger points, remote acupuncture, or injection techniques—may all provide benefit through distinct but overlapping physiological effects. The immediate pain relief often experienced during needling likely involves fast-acting neural mechanisms including hyperstimulation analgesia and disruption of MTrP circuits via the descending pain inhibitory system, while longer-term benefits may involve slower hormonal and anti-inflammatory changes.

For clinicians, the findings support the importance of eliciting local twitch responses during dry needling, as this appears to be associated with biochemical changes and reduced MTrP irritability. The remote effects of needling suggest that treating distal points or contralateral points may be beneficial, particularly when local needling is contraindicated or poorly tolerated. The substantial overlap between MTrPs and acupoints provides a bridge between Western and Eastern medical approaches, potentially allowing clinicians to integrate both traditions. However, the review also notes that many clinical trials have been small and of poor quality, highlighting the need for larger, well-designed studies to confirm optimal needling techniques and protocols.