Laser therapy for trapezius trigger point pain showed no advantage over sham in a blinded trial

A randomized, double-blind, sham-controlled trial enrolled 52 adults with chronic trapezius pain and myofascial trigger points, assigning them to either active near-infrared laser therapy or an identical inactive procedure across eight sessions over four weeks. Active laser treatment did not outperform the sham condition on pain, trigger point count, skin temperature, or overall perceived improvement, though cervical function showed a statistically significant advantage in the active group.

What the study found

The primary finding is null: active laser therapy was not superior to sham treatment for the main outcomes of pain intensity, number of active trigger points, or skin temperature over the four-week intervention period. Effect sizes for these non-significant comparisons were very small, suggesting the absence of a meaningful between-group difference rather than simply insufficient statistical power.

One outcome did reach statistical significance: cervical function improved more in the active laser group than in the sham group, with a modest effect size. The authors interpret this as a possible functional benefit that did not translate into subjective pain relief, though the mechanism and clinical relevance of this isolated finding remain unclear.

Notably, both groups reported clinically meaningful reductions in pain over the course of the study. This pattern — improvement in both arms — is consistent with a strong placebo response, natural symptom fluctuation, or non-specific effects of repeated clinical contact, and makes it difficult to attribute any benefit specifically to the laser intervention.

Adverse events were reported as mild and infrequent, with transient warmth at the treatment site being the most common. No serious safety concerns were identified in this population.

Limits worth knowing

The trial was conducted at a single site and enrolled 52 participants, which, while adequate for a pilot-level RCT, limits generalizability. The population was adults aged 18 and older with chronic trapezius pain, so findings may not extend to other muscle groups, pain types, or age profiles. The intervention was fixed at a single energy dose and wavelength, meaning results cannot speak to whether different parameters might produce different outcomes. The study duration was four weeks with eight sessions, leaving longer-term effects unmeasured. No funding source is disclosed in the available information, so potential conflicts of interest cannot be assessed. The trial was registered prospectively on a Brazilian registry, supporting methodological transparency.

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