Effectiveness of Photobiomodulation Therapy in the Treatment of Myofascial Pain Syndrome of the Upper Trapezius Muscle: A Systematic Review and Meta-Analysis

Myofascial pain syndrome (MPS) is a chronic condition affecting approximately 74% of patients visiting outpatient clinics with muscle pain. It's characterized by trigger points—localized tender spots in tight muscle bands that cause pain, stiffness, and limited movement. The upper trapezius muscle, which spans from your neck to your shoulder, is commonly affected. While various treatments exist including medications, injections, and physical therapies, photobiomodulation therapy (PBMT)—previously known as low-level laser therapy—has emerged as a promising option.

PBMT uses specific wavelengths of light to stimulate healing and reduce pain, but results across studies have been inconsistent, and no comprehensive analysis had examined its effectiveness specifically for upper trapezius trigger points.

Researchers conducted a thorough systematic review and meta-analysis, searching multiple medical databases through December 2020 for randomized controlled trials testing PBMT in patients with upper trapezius MPS. They included 17 studies with 944 total patients, all adults with chronic myofascial pain and confirmed trigger points in the upper trapezius muscle. The studies compared PBMT alone or combined with exercise against various control treatments including placebo laser, medical treatment, other physical therapy modalities, and manual therapy. They assessed study quality using standardized scales and combined results statistically to determine overall effectiveness for pain reduction and pressure pain threshold (PPT)—a measure of how much pressure triggers pain.

The analysis revealed significant benefits from PBMT treatment. When used alone, PBMT showed moderate effectiveness in reducing pain with a standardized mean difference of -0.54, meaning meaningful pain reduction compared to control treatments. However, PBMT combined with exercise was even more effective, producing large effect sizes for both pain reduction (-0.80) and improved pressure pain threshold (1.11). This combination approach consistently outperformed control treatments across multiple measures.

The effects were sustained at follow-up periods ranging from 4 weeks to 6 months. Studies using higher-intensity laser therapy and combination treatments showed particularly strong results. Of the 17 studies analyzed, 12 were rated as high quality, though the overall evidence quality was considered low to moderate due to variations in treatment protocols and some methodological limitations.

This comprehensive review provides strong evidence that photobiomodulation therapy is an effective treatment for myofascial pain in the upper trapezius muscle, particularly when combined with exercise. For patients suffering from chronic neck and shoulder pain due to trigger points, PBMT offers a non-invasive, drug-free treatment option that can provide meaningful pain relief and improved function. The therapy appears to work by stimulating the body's natural healing processes, increasing blood flow, reducing inflammation, and modulating pain signals. Clinicians can feel confident recommending PBMT, especially as part of a comprehensive treatment plan that includes therapeutic exercises.

However, the review also highlights the need for standardized treatment protocols, as studies used varying laser parameters, treatment durations, and energy levels, making it difficult to establish optimal treatment guidelines.