Muscle Knots: The Science of Trigger Points and the 2024 Breakthrough

Why It Matters

Anyone who has ever felt their neck after a long day at the desk knows the sensation: a hard, painful lump somewhere between the shoulder blade and the spine. Press on it, and the pain radiates to your temple, arm, or down your back. This is what people call a «muscle knot» — and what medicine calls a myofascial trigger point.

By some estimates, myofascial pain syndrome affects up to 30% of the world’s population. It ranks among the most common causes of chronic neck, back, and shoulder pain. Yet scientists still debate what these «knots» actually are and why they form.

In 2024, a team from Shandong University published a paper in Anesthesiology that described, for the first time, a specific molecular mechanism behind muscle knot formation. The discovery of the COL1A1/PDGFR-α/JAK2/STAT3 axis is not just another hypothesis — it is an experimentally validated pathway from molecule to pain. And potentially, a key to fundamentally new treatments.

The Classic Theory: Energy Crisis

To appreciate the 2024 breakthrough, we first need to understand what we «knew» before.

Myofascial trigger point (MTrP) — a hyperirritable nodule within a taut band of skeletal muscle. When pressed, it produces local pain, referred pain in distant areas, and sometimes an involuntary twitch of the muscle bundle.

The classic «integrated hypothesis» by David Simons, formulated in the 1990s, describes a muscle knot as a vicious cycle:

1. Initiating event — microtrauma, overload, prolonged static tension
2. Acetylcholine excess — the neuromuscular junction releases too much neurotransmitter
3. Stuck contraction — several sarcomeres lock into a shortened state
4. Ischemia — the spasming area compresses capillaries, reducing blood flow
5. Energy crisis — without oxygen, ATP synthesis drops; without ATP, the calcium pump cannot relax the muscle fiber
6. Pain — hypoxia and tissue damage release a «cocktail» of pain mediators: substance P, bradykinin, prostaglandins, cytokines

Sarcomere — the smallest contractile unit of a muscle. Imagine two sets of combs interlocked with each other. When the muscle contracts, these «combs» — the proteins actin and myosin — slide past one another, shortening the sarcomere. To slide apart again, they need energy in the form of ATP.

The model is elegant and logical. But here is the problem: it describes a closed loop without explaining what exactly, at the molecular level, initiates and sustains this state. Electrophysiologists have recorded spontaneous electrical activity in trigger point zones for decades — but what drives it?

The Breakthrough: COL1A1 → PDGFR-α → JAK2/STAT3

In July 2024, Yu Liu and colleagues from Shandong University asked a simple question that, surprisingly, had not been investigated before: if a trigger point is a pathological tissue process, which receptor tyrosine kinases are activated in it?

Receptor tyrosine kinases (RTKs) — protein receptors on cell surfaces that, when activated, trigger cascades of intracellular signals. Think of them as «antennas» receiving molecular messages. PDGFR-α is one such receptor, typically associated with cell growth and wound healing.

The researchers biopsied the upper trapezius muscle from 11 patients with chronic myofascial pain and 7 healthy volunteers. Using an RTK phosphorylation microarray, they screened dozens of receptors simultaneously — and found that one stood out dramatically from the rest.

PDGFR-α — platelet-derived growth factor receptor alpha. Its activation in trigger point tissues was significantly elevated (p < 0.001). Moreover, the level of activated PDGFR-α correlated with pain intensity on the visual analog scale (r = 0.711). The worse the pain, the more phosphorylated receptor in the tissue.

But what activates this receptor? The classic PDGFR-α ligand is PDGF-AA. Its blood levels in patients were also elevated (5.97 ng/ml vs. 3.74 in controls). However, the real surprise came next.

Collagen as a Signaling Molecule

Using mass spectrometry and co-immunoprecipitation, the authors discovered that PDGFR-α physically binds to COL1A1 — collagen type I, the primary structural protein of connective tissue.

This was unexpected. Collagen I is a «scaffolding» protein that everyone considered a passive structure — essentially, the rebar of tissues. But it turns out COL1A1 also functions as a signaling molecule: it binds PDGFR-α and activates it directly, without the classical PDGF ligand.

Molecular docking revealed specific binding sites: amino acids LYS35–ASP846, GLU55–THR894, HIS845–ARG34.

From Molecule to Pain

The authors then validated the entire chain in a rat model. Here is the complete cascade:

1. COL1A1 accumulates in damaged muscle areas — from microtrauma, overload, chronic tension
2. COL1A1 binds to PDGFR-α and triggers its phosphorylation
3. Activated PDGFR-α engages the JAK2/STAT3 pathway — a well-known inflammatory signaling cascade
4. JAK2/STAT3 upregulates pro-inflammatory cytokines: IL-1β, IL-6, TNF-α
5. Simultaneously, myosin light chain kinase (MLCK) is activated, phosphorylating myosin
6. Phosphorylated myosin causes sustained contraction — sarcomeres shorten from 2.13 μm to 1.63 μm
7. The result: a contraction knot — sustained contraction + inflammation + pain

JAK2/STAT3 — one of the key intracellular signaling pathways. JAK2 is a kinase enzyme that, when activated, phosphorylates the transcription factor STAT3. Activated STAT3 enters the cell nucleus and switches on genes for inflammation and contraction. This pathway is well known in oncology — and now it turns out to be involved in muscle pain.

The critical finding: when the researchers blocked this pathway — either by knocking down PDGFR-α or by using the JAK2/STAT3 inhibitor AZD1480 — pain behavior in rats decreased, sarcomeres returned to normal length, and inflammatory cytokine levels dropped.

Why Muscle Knots Are Harmful

«Just some neck tension, ” someone might say. But myofascial trigger points are more than mere discomfort. Here is what they actually threaten:

Pain chronification. A constant stream of pain signals from trigger points causes central sensitization — the nervous system begins to «turn up the volume» on pain at the spinal cord level. Over time, less and less stimulus is needed to produce pain. A touch that previously went unnoticed starts hurting — a phenomenon called allodynia.

Chain reaction. A single trigger point can activate others — in neighboring muscles, antagonist muscles, even in areas far from the original site. Someone who came in with neck pain may find painful spots in their lower back and thighs six months later.

Sleep and mental health disruption. Chronic pain wrecks sleep architecture. Poor sleep amplifies pain sensitivity. Add increased risk of anxiety and depression — which in turn increase muscle tension. Three interlocking vicious cycles.

Loss of function. Restricted range of motion, guarding postures, reduced strength. Studies show that trigger points in the trapezius muscle significantly reduce neck mobility and increase the risk of chronic tension-type headaches.

The Scientific Debate: Do Trigger Points Even Exist?

It would be dishonest not to mention that trigger points remain one of the most contested topics in medicine.

Skeptics, led by John Quintner from the IASP (International Association for the Study of Pain), point to serious issues:

• Different clinicians palpating the same patient often locate trigger points in different places
• Treatment effects are difficult to distinguish from placebo
• Diagnosis relies on circular logic: «it hurts → found a tender spot → therefore the spot causes pain»

Proponents counter that:

• Biochemical changes in trigger point zones are reproducible — substance P, cytokines, local acidosis
• 2024 ultrasound elastography showed trigger points are objectively stiffer than surrounding tissue, with measurable parameters
• The Liu et al. study provides the first concrete molecular mechanism

The modern compromise (as of 2024–2025): painful muscle lumps are a real clinical phenomenon. But they are probably not a separate «disease» — rather, a combination of local muscular changes and overall nervous system sensitivity. The PDGFR-α work bolsters the «peripheral» component, but the role of central sensitization in chronification remains crucial.

How to Get Rid of Them: What the Evidence Says

Systematic reviews from 2024–2025 allow us to rank methods by strength of evidence:

Dry needling — the most studied method. Meta-analyses show moderate-to-strong short-term pain reduction and increased pain thresholds. Effects last up to 6 weeks. Requires a trained practitioner.

Dry needling — insertion of a thin needle directly into the trigger point. Unlike acupuncture, there are no «meridians» — the needle targets the spasm zone specifically, provoking a local twitch response followed by muscle relaxation.

Massage and manual therapy — moderate evidence. Friction massage of trigger points raises pain thresholds and increases range of motion. Multiple sessions work better than one. Safe, accessible, pairs well with exercise.

Extracorporeal shockwave therapy (ESWT) — emerging evidence for trigger points in the lower back. Evidence quality remains low to moderate.

Foam rolling and self-massage — reduces soreness and improves mobility in the short term. But rigorous data specifically on clinical trigger points are sparse. Cheap, safe, and convenient for daily use.

Exercise — the cornerstone of any protocol. Stretching + strengthening target muscles + ergonomic correction. Without this, all other methods deliver only temporary relief.

Trigger point injections — a 2023 meta-analysis showed moderate advantage over medication for acute myofascial pain. Practitioners use lidocaine, botulinum toxin, or even just saline — interestingly, the «dry needle» effect is often comparable to injection.

Critical Assessment

Strengths of the Liu et al. study:

• First research to use an unbiased RTK screen — they did not test one hypothesis but searched across dozens of receptors
• Combined human patient data with an animal model
• Complete chain from molecular binding to behavioral changes
• Both pharmacological and genetic confirmation of causality — blocking the pathway eliminates symptoms

Limitations:

• Small human sample: only 11 patients and 7 controls. Clinical significance requires hundreds
• The rat trigger point model — blunt trauma to the gastrocnemius — only approximates human pathology
• Therapeutic application of PDGFR-α or JAK2/STAT3 inhibitors for muscle pain is years of clinical trials away

Open questions:

• Is the COL1A1/PDGFR-α axis a universal mechanism for all trigger points, or just one of several pathways?
• How does this molecular pathway connect to the effectiveness of existing treatments — dry needling, massage, exercise?

Disclaimer. The described study was published in the peer-reviewed journal Anesthesiology (impact factor ~9). This is serious work — but a single study, however excellent, is not the final word. The results need independent replication. This article is a popular science review, not medical advice.

What Comes Next

The discovery of the COL1A1/PDGFR-α/JAK2/STAT3 axis opens several avenues:

New therapeutic targets. JAK2 inhibitors already exist — ruxolitinib, baricitinib, tofacitinib. They are used in rheumatology and oncology. Theoretically, local injection of such drugs into the trigger point zone could be more effective than existing injections. But this remains pure hypothesis for now.

Objective diagnostics. If phosphorylated PDGFR-α levels correlate with pain intensity, this could become the first objective biomarker of myofascial pain — replacing subjective palpation.

Bridging the camps. The Liu et al. data could reconcile trigger point skeptics and proponents: there is an objective molecular substrate, but it is tightly linked to neuroinflammation and central sensitization. Both sides of the debate are partially right.

In the meantime, if your neck hurts right now — stand up, stretch, move your shoulders. Exercise is the only method with zero cost and zero side effects that works whether you believe in «mysterious trigger points» or «just tense muscles.» Whichever camp turns out to be right.

Frequently Asked Questions

Are muscle knots the same as muscle spasms?

No. A muscle spasm is an involuntary contraction of an entire muscle or a large portion of it, usually brief. A muscle knot is a sustained contraction of just a few sarcomeres within a single muscle bundle. It can persist for weeks or months, unlike a spasm that typically resolves within minutes.

Can I identify a trigger point on my own?

Typical signs during self-palpation: a firm nodule in the muscle, sharp tenderness when pressed, and pain that radiates to another area — for instance, from the neck to the temple. However, research shows that even professionals do not always agree when palpating the same patient. If the pain is chronic or significantly affects your quality of life, consult a specialist rather than relying on self-diagnosis.

Does stress really cause muscle knots?

Yes, the link is supported by research. Psychological stress raises muscle tone via sympathetic nervous system activation, impairs microcirculation, and lowers pain thresholds. During exam periods, for example, students show significantly more active trigger points in the trapezius muscle. But stress is more of a perpetuating factor than the sole cause.

How effective is foam rolling against trigger points?

Foam rolling moderately reduces muscle soreness and improves mobility — systematic reviews confirm this. However, rigorous data specifically on clinical trigger points remain limited. A foam roller is a solid daily prevention tool, but for persistent chronic pain, it is unlikely to replace targeted massage, dry needling, or an exercise program.

When can we expect new drugs based on the PDGFR-α discovery?

Not anytime soon. The Liu et al. findings are basic science: they demonstrate a molecular mechanism in rats and a small group of patients. Years of additional research are needed before clinical trials of targeted therapy — validation in larger cohorts, safety assessment of local JAK2 inhibitor administration, and dosing protocol development. An optimistic estimate is 5–10 years before the first clinical protocols emerge.