Ultrasound for Trigger Points
What Ultrasound and Biopsies Reveal About Trigger Points and Why Dry Needling Works
If you’ve ever felt a stubborn knot in your upper back or neck that just wouldn’t go away, you’re not alone. Myofascial trigger points—commonly called “muscle knots”—are among the most frequent causes of chronic musculoskeletal pain. These points often feel like tight bands or nodules in the muscle and can cause local or referred pain, movement restriction, and discomfort during daily activities.
The upper trapezius is one of the most common muscles affected by trigger points, especially among people with stress, poor posture, or high physical demand.
A new 2025 study published in Scientific Reports (2025) takes a unique approach to understanding these trigger points—not just through symptoms or palpation, but by combining ultrasound imaging and muscle biopsy. Even more importantly, the researchers investigated what happens to these trigger points after dry needling, offering new insight into how and why this technique works.
Muscle Ultrasound on Upper Trapezius
Key Points
Trigger points in the upper trapezius were thicker, stiffer, and had reduced blood flow compared to healthy muscle.
Dry needling significantly reduced muscle stiffness and improved local circulation within just one hour.
Pain levels dropped by nearly 3 points on the visual analog scale.
Biopsies showed muscle fiber atrophy, fibrosis, inflammation—and no contraction knots.
These findings suggest a new way of understanding how trigger points form and how dry needling helps resolve them.
How the Study Was Designed to Evaluate Trigger Points
Researchers at Beijing Chao-Yang Hospital recruited 49 adults with active myofascial trigger points in the upper trapezius. Each participant had one painful side and one healthy side, which was used as a comparison. Here's what made this study unique:
Ultrasound imaging was used to measure:
Muscle and fascia thickness
Tissue stiffness using shear wave elastography (SWE)
Blood flow using Doppler ultrasound, including:
Resistance Index (RI) – how restricted the blood flow is
Vascularity Index (VI) – how many blood vessels are perfusing the muscle
Peak Systolic Velocity (PSV) – blood flow speed
Pain levels were recorded using a Visual Analog Scale (VAS) before and one hour after dry needling.
Muscle biopsies were performed on 5 participants to analyze tissue under a microscope.
All participants received ultrasound-guided dry needling into the affected trapezius muscle, and imaging and pain scores were repeated 60 minutes later.
Study Findings
| Findings | What It Means (in Plain English) |
|---|---|
| Upper trapezius trigger points were thicker and stiffer than healthy muscle | The affected muscle was swollen and tight, confirming what you feel as a knot is a real structural change. |
| Blood flow to the trigger point was significantly reduced | Poor circulation may contribute to pain, fatigue, and the muscle’s inability to heal. |
| Dry needling reduced thickness and stiffness within 1 hour | Needling quickly helped restore normal texture and flexibility to the muscle. |
| Vascularity index increased fivefold after dry needling | Blood flow improved dramatically—more oxygen and nutrients can reach the area. |
| Pain dropped nearly 3 points on the visual analog scale (VAS) | Patients felt significantly better right after treatment. |
| Muscle biopsies showed fibrosis, fat replacement, and inflammation—but no contraction knots | The pain is caused by tissue damage and inflammation, not just muscle spasm or tension. |
| Mitochondrial changes suggest local metabolic stress | The muscle is energy-deprived and working inefficiently—likely contributing to pain and fatigue. |
What Ultrasound Revealed Before and After Dry Needling
Before treatment, the trigger points clearly showed measurable dysfunction compared to the healthy side:
Muscles were thicker: 11.24 mm vs. 10.00 mm
Tissue was stiffer: 32.28 kPa vs. 19.16 kPa
Blood flow was reduced:
Higher resistance (RI = 0.86 vs. 0.78)
Lower vascularity (VI = 2.53 vs. 8.23)
After just one session of dry needling, dramatic changes occurred:
Muscle thickness dropped to 9.64 mm, even thinner than the healthy side
Stiffness reduced to 24.14 kPa
Vascularity improved 5x, jumping to 12.90
Pain scores decreased from 7.86 to 5.00 on average—a drop of nearly 3 points in just 1 hour
These changes suggest dry needling not only relieves pain but also improves muscle structure and restores circulation.
What Biopsies Reveal About Trigger Point Tissue
Five patients consented to undergo muscle biopsy in the area of their upper trapezius trigger points. What researchers found was both fascinating and surprising:
Muscle fiber atrophy: Instead of healthy contractile tissue, many fibers showed signs of degeneration.
Fibrofatty infiltration: Muscle was partially replaced by fibrous tissue and fat, contributing to stiffness.
Inflammation: T-cells surrounded small blood vessels, indicating immune system involvement.
No contraction knots: Despite being a classic theory in myofascial pain, no true contraction knots were found.
Mitochondrial changes: Suggestive of chronic stress and energy depletion in the muscle.
These findings challenge the idea that trigger points are simply localized knots of over-contracted muscle. Instead, they appear to be zones of tissue degeneration, fibrosis, inflammation, and impaired circulation.
How Dry Needling Treats Trigger Points on a Physiological Level
This study provides compelling evidence that dry needling offers more than temporary relief. It likely works through multiple mechanisms:
Restoring blood flow to ischemic, oxygen-deprived muscle
Reducing stiffness by disrupting fibrotic tissue and allowing normal elasticity
Improving mitochondrial activity and cellular function
Modulating inflammation, possibly influencing local immune signaling
Affecting both muscle fibers and surrounding fascia, which is often overlooked
In short, dry needling appears to mechanically and physiologically remodel dysfunctional tissue, not just stimulate a twitch.
Why This Matters for People with Chronic Neck and Shoulder Pain
If you’ve been told “you’re just tight” or “it’s probably stress,” this study provides something invaluable: proof that trigger points involve real, measurable tissue dysfunction.
Here’s what this means for you:
You don’t need to feel a twitch for treatment to work. Structural and blood flow improvements occurred even without twitch responses.
It’s not just muscle—it’s fascia, blood vessels, and inflammation too.
Your pain isn’t in your head. Ultrasound and biopsy show it’s in your tissue.
Dry needling may help even if other treatments didn’t. Especially if you haven’t addressed the fascial and vascular side of your pain.
Ready to Try Dry Needling?
Whether you’re struggling with upper trapezius pain, tension headaches, or limited mobility, dry needling may help restore muscle function and reduce pain—quickly and safely.
📍 Conveniently located in New York City
🧠 Experts in trigger point therapy, acupuncture, and dry needling
Book your appointment today with the experts at Morningside Acupuncture, the top-rated acupuncture and dry needling clinic in New York City.
Let us help you move better, feel stronger, and live pain-free.
Related Questions:
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Myofascial trigger points are hypersensitive spots in muscle tissue, often felt as tight knots or bands that can cause local or referred pain. They're especially common in muscles like the upper trapezius and are linked to overuse, poor posture, stress, and injury.
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Trigger points are most commonly diagnosed through palpation. A skilled practitioner feels for taut bands in the muscle that are tender to the touch and may reproduce referred pain. While palpation remains the standard, this study shows how ultrasound can provide additional objective confirmation.
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Dry needling is a style of acupuncture that uses the same type of acupuncture needle to target trigger points and dysfunctional muscle. It’s often used to relieve muscle stiffness, reduce pain, and restore mobility. Unlike traditional acupuncture, which may follow meridian theory, dry needling is focused on musculoskeletal structure and function.
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The study found that trigger point areas in the upper trapezius are:
Thicker and stiffer than healthy muscle
Poorly perfused (lower blood flow)
Associated with pain and structural changes seen on biopsy
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One hour after treatment:
Muscle stiffness and thickness decreased
Blood flow improved dramatically
Pain scores dropped by nearly 3 points
These changes were confirmed with ultrasound imaging and support the idea that dry needling can quickly normalize muscle function.
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SWE is an advanced ultrasound technique that measures tissue stiffness in real time. In this study, it helped quantify how stiff trigger points were before treatment—and how much that stiffness improved after dry needling. It’s a valuable tool for understanding and tracking myofascial dysfunction.
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Yes. Although some clinicians aim for a local twitch response during dry needling, this study showed significant improvement in tissue properties and pain reduction without relying on twitch response alone. Clinical outcomes matter more than the twitch itself.
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Anyone dealing with:
Chronic upper trapezius or neck pain
Persistent muscle knots that don’t respond to massage or stretching
Tension headaches originating from the upper shoulders
Stiffness, tightness, or weakness after injury
Sources:
Cao, W., Li, Y., Sun, H., Ge, H., Guo, R., & Lyu, X. (2025). Ultrasound features of myofascial trigger points: A multimodal study integrating preliminary histological findings from the upper trapezius. Scientific Reports, 15, 20510. https://doi.org/10.1038/s41598-025-05869-2
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