Equis ISSN 2398-2977

Musculoskeletal: laser therapy

Synonym(s): Low level laser therapy, LLLT, Photobiomodulation

Contributor(s): Graham Munroe, Ronald Riegel


  • Low-level laser therapy (LLLT) has been a popular modality in the physiotherapeutic management of musculoskeletal injuries and skin wounds in humans, dogs and horses for over 25 years. There is preponderance of scientific literature available in both the human and veterinary fields. There are currently a number of studies being conducted at numerous veterinary schools. This scientific evidence together with a large number of documented clinical case studies allows laser therapy to be deemed: Evidence based healthcare.
  • In 2012 the World Association of Laser Therapy (WALT) and the North American Association of Light Therapy (NAALT) adopted the nomenclature Photobiomodulation (PBM) to be used as the term for LLLT.
  • High-power lasers (>0.5 Watts) are used in the Veterinary field for both surgical and physiotherapeutic applications.
  • Low-power lasers (<0.5 Watts) are only used in superficial physiotherapeutic applications such as the management of wounds.
  • Laser therapy uses light wavelengths of between 600 and 1200 nm with unique properties of a single wavelength (monochromatic), waves in phase (coherence) and collimation (waves in parallel). As a result, it can deliver large amounts of energy to a small region over a short period of time.
  • Wavelength determines the depth of penetration within the tissue and the power (in Watts) determines the number of photons that reach that depth. Studies are underway to try to isolate ideal wavelengths for individual clinical applications.
  • The substance which is used to generate the laser determines its wavelength and can include helium neon (HeNe) 632 nm, gallium arsenide (GaAs) 904 nm and gallium-aluminum-arsenide (GaAlAs) 820 nm. Most therapeutic lasers are diode lasers.
  • The interaction of the laser light with tissue depends on the wavelength of the light, the power of the laser, the nature of the tissue itself, and the way it is applied. The effects on the tissue are photobiochemical rather than temperature-based. Current research and proposed theories include: stimulation of cytochrome and mitochondrial respiratory activity resulting increased ATP production, the release of nitric oxide and reactive oxygen species; plus numerous virtual biochemical cascades of events concluding in a state of analgesia, a modulation of the inflammatory cycle and an increase in circulation.
  • The energy density that is applied (J/cm2) as well as the specific tissue upon which it is targeted is important in measuring the effect of laser treatments. 
  • The wavelength of the laser will determine the depth of penetration of the beam. He-Ne lasers with wavelength of 632 nm (visible red beam) have been found to penetrate up to 2 cm through skin at a level adequate to stimulate the cells. Wavelengths of 700 -1100 nm (infrared) penetrate further and are used to treat deeper structures such as tendons and ligaments. A general rule of physics applies here that states the higher the wavelength up to 1100 nm, the deeper the penetration within the tissue.
  • There is considerable evidence in the literature proving that He-Ne or GAA diode lasers significantly accelerate wound healing, modulate the inflammatory reaction and provide analgesia (this was done at a very low dose).
  • Proceedings from the American Society of Lasers in Medicine and Surgery for the last three years have published a great deal of evidence supporting the efficacy of wound healing, eg:
    • Triple-blind, sham-controlled in vivo human study identical skin wound were created in 22 volunteers aged 21 +/-1 year.
    • Randomly placed in a control, sham laser or laser treatment group.
    • 8 J/cm2, 820 nm laser.
    • Measured epithelial migration.
    • 153% greater wound contraction at day 6 in the laser group.
  • There is a biochemical cascade of events that is the result of the reduced reaction time for the oxidation of cytochrome C therefore increasing the respiratory rate of the cell. Stimulation of fibroblasts to myofibroblasts which would increase the rate of granulation and wound contraction is one example. Cellular research has also demonstrated that LLLT (PBM) reduced experimentally induced inflammation by 20-30%. The ideal wavelength is still being determined for this; current literature suggests 810 nm.
  • LLLT (PBM) has been used extensively in treating joint disease in the human, including degenerative osteoarthritis of the knees and cervical vertebrae, with reports of improvement in range of motion, pain relief and decrease in muscle spasm. A variety of lasers with different wavelength and power outputs, duration and frequency of treatment have been used.  In all of the studies the common denominator was that all laser therapy worked to some degree. Two studies reported pain relief in both RA (rheumatoid arthritis) and fibromyalgia human patients post irradiation with LLLT. One study displayed an ultrasound assessed decrease in tendon diameter of tenosynovitis diagnosed tendons after laser application. LLLT (PBM) can be applied in conjunction with traditional pharmaceutical approaches such as glycosaminoglycan   Polysulfated glycosaminoglycan  .
  • A retrospective paper given at the April 2015 meeting of the American Society of Lasers in Medicine and Surgery depicted success in the treatment of OA in all 35 cases of osteoarthritis within the coxofemoral joint in the dog.
  • It is difficult to compare results of the various studies utilizing laser therapy. Often human studies are extrapolated to fit the animal model.  Parameters often vary with different conditions treated, different dosages utilized and different outcome measures recorded. LLLT (PBM) is a proven scientific and clinical evidenced based modality.  Further investigative work is always warranted as the technology and new software programs appear. When surveyed, practicing physiotherapists corroborated the beneficial clinical effects of LLLT (PBM), and the FDA (Federal Drug Agency, USA) has approved the use of LLLT (PBM).


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
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  • Cuervo B et al (2014) Hip osteoarthritis in dogs: a randomized study using mesenchymal stem cells from adipose tissue and plasma rich in growth factors. Int J Mol Sci 15 (8), 13437-13460. doi: 10.3390/ijms150813437 PubMed.
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  • Fahie M A et al (2013) A randomized controlled trial of the efficacy of autologous platelet therapy for the treatment of osteoarthritis in dogs. JAVMA243(9), 1291-1297. doi: 10.2460/javma.243.9.1291 PubMed.
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Other sources of information

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