The Science of Laser Therapy
Laser therapy, also known as photobiomodulation, is a non-invasive treatment that uses specific wavelengths of light to influence how cells function. Unlike surgical lasers, it is not designed to cut, burn, or heat tissue. Instead, its effects are primarily photochemical: light energy is absorbed by cells and triggers biologic changes that can help reduce inflammation, improve circulation, and support tissue recovery.
The most important target appears to be the mitochondria, the part of the cell responsible for energy production. In the attached MLS literature, synchronized 808 nm and 905 nm wavelengths are described as interacting with different parts of the mitochondrial respiratory chain. The 808 nm wavelength is associated with cytochrome oxidase (complex IV), while 905 nm is described as interacting with multiple respiratory complexes. The result is increased ATP production, which gives cells more energy to repair and recover.
Preclinical muscle studies in the same literature also found that laser exposure increased MyoD, an important marker of muscle-cell differentiation, by about 26%, while also increasing collagen I expression and reducing enzymes involved in tissue breakdown. In practical terms, that suggests laser therapy may help shift injured tissue toward a more organized healing response.
Laser therapy does not appear to work simply by masking pain. The literature suggests that it may actually modulate inflammatory pathways. In the tendon-healing literature you attached, laser treatment is described as reducing PGE2, inhibiting cyclo-oxygenase, and influencing fibroblast metabolism and collagen deposition. In an experimental sheep tendinopathy model, laser treatment was associated with an anti-inflammatory effect, reduced cellularity, decreased vascular changes, and improved collagen fiber organization.
Additional clinical evidence in the attached MLS compendium reports that, after hip arthroplasty, active photobiomodulation was associated with reduced pain and lower TNF-a and IL-8 levels compared with placebo, which supports the idea that laser therapy may influence inflammatory signaling in living tissue.
Another proposed mechanism is improved microcirculation. Better local circulation may help deliver oxygen and nutrients to injured tissue while also helping clear inflammatory metabolites. The TMJ review describes increased vasodilation and pain threshold, while the Japanese sports-injury review explains pain relief in part through improved blood flow and washout of pain-producing substances.
That mechanism also appears in human knee osteoarthritis research. In one placebo-controlled trial included in the attached MLS literature, patients treated with laser therapy had significant improvement in pain, pressure sensitivity, and joint flexion, along with thermographic evidence of improved microcirculation in the treated area.
The strongest clinical evidence today supports laser therapy as a treatment to improve pain and function, especially in musculoskeletal conditions such as knee osteoarthritis. The AAOS 2021 guideline states that FDA-approved laser treatment may be used to improve pain and function in patients with knee osteoarthritis, although the strength of recommendation is listed as limited.
The attached Australian review highlights a later meta-analysis that included 22 randomized controlled trials and 1,063 patients, finding strong evidence for reduced pain and disability with low-level laser therapy in knee osteoarthritis. That review also emphasizes an important point: outcomes were best when recommended treatment parameters were used, including approximately 4-8 J per point at 785-860 nm and 1-3 J per point at 904 nm.
One of the most important scientific takeaways is that not all laser therapy is the same. Results depend on the wavelength, power, pulse pattern, dose, treatment location, and number of sessions. This is why some studies are positive and others are less impressive: different devices and protocols can produce very different biologic effects. The Australian review specifically found that clinical benefit was closely tied to using the right dose, and the sheep tendon study suggests the same, with the lower-dose protocol showing more favorable anti-inflammatory and collagen-organizing effects than the higher dose.
Laser therapy is best understood as a biologic signaling treatment. It is not simply a heat treatment, and it does not work by “covering up” symptoms alone. When the correct wavelength and dose are used, the attached literature suggests that laser therapy can increase cellular energy production, modulate inflammation, improve local circulation, and reduce pain. The strongest human evidence currently supports improvements in pain and function, while the more detailed tissue-repair mechanisms are supported most strongly by laboratory and preclinical studies. That distinction matters, because it allows us to discuss laser therapy accurately: as a science-based, non-invasive treatment with real biologic effects, but one whose results depend heavily on using the right protocol for the right condition.
