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Musculoskeletal: laser therapy

ISSN 2398-2977

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

Podcast: Musculoskeletal: laser therapy


  • 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, with scientific literature available in both the human and veterinary fields. 
  • 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. 
  • The proposed theories of action 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. 
  • There is literature demonstrating that He-Ne or GAA diode lasers accelerate wound healing, modulate the inflammatory reaction and provide analgesia.



  • Time-efficient, non-invasive, non-pharmacological anti-inflammatory treatment.


  • The exact parameters for treating individual types of problems are not very clear. 
  • Repeated treatments are required to achieve long-lasting effects.
  • Costs of the machine. 
  • Lasers can be dangerous, particularly to the eye (retina) of the operator, patient or handler. Protective eyewear is a must when using any Class III or Class IV laser!

The beam of an infrared laser is invisible making it even more potentially dangerous.



Veterinarian expertise
  • Physiotherapist requires an understanding of the science behind LLLT (PBM) and training in proper application techniques.

Materials required

Minimum equipment
  • Low Level Laser: 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.


  • Results from equine research suggest that, when applying laser to a subcutaneous structure in the horse, the area should be clipped and cleaned beforehand to improve penetration of the laser beam.
  • Use of alcohol without clipping was not associated with an increase in light transmission.

Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Haussler K K, Manchon P T, Donnell J R & Frisbie D D (2020) Effects of low-level laser therapy and chiropractic care on back pain in quarter horses. J Equine Vet Sci 86 PubMed.
  • Dahlgren L A (2018) Regenerative medicine therapies for equine wound management. Vet Clin North Am Equine Pract 34 (3), 605-620 PubMed.
  • Duesterdieck-Zellmer K F et al (2016) Ex vivo penetration of low-level laser light through equine skin and flexor tendons. Am J Vet Res 77 (9), 991-9 PubMed.
  • Ryan T & Smith R (2007) An investigation into the depth of penetration of low level laser therapy through the equine tendon in vivo. Ir Vet J 60, 295-299 PubMed.
  • Brousseau L et al (2005) Low level laser therapy (Classes I, II and III) for treating rheumatoid arthritis (Cochrane review). Cochrane Database Syst Rev 19 (4), CD002049 WileyOnline.
  • Porter M (2005) Equine rehabilitation therapy for joint disease. Vet Clin North Am Equine Pract 21 (3), 599-607 PubMed.
  • Gur A et al (2003) Efficacy of different therapy regimes of low power laser in painful osteoarthritis of the knee: a double blind and randomised controlled trial. Lasers Surg Med 33 (5), 330-338 PubMed.
  • Ramsey D W & Bashford J R (2000) Laser therapy in horses. Comp Cont Educ 22, 263-272.
  • Petersen S L et al (1999) The effect of low level laser therapy (LLLT) on wound healing in horses. Equine Vet J 31 (3), 228-231 PubMed.
  • Fretz P B & Li Z (1992) Low energy laser irradiation treatment for second intention wound healing in horses. Can Vet J 33 (10), 650-653 PubMed.
  • Martin B J & Kilde A M (1987) Treatment of chronic back pain in horses: Stimulation of acupuncture points with a low powered infrared laser. Vet Surg 16 (1), 106-110 PubMed.
  • Kaneps A J, Hultgren B D, Riebold T W & Shires G M H (1984) Laser therapy in the horse: Histopathological response. Am J Vet Res 45 (3), 581-582 PubMed.

Other sources of information

  • Riegel R J et al (2015) Efficacy of Photobiomodulation in the Treatment of Osteoarthritis with the Coxofemoral Joint of the Canine. In: Proc American Society of Lasers in Medicine and Surgery.
  • Fox S (2014) Pain Management in Small Animal Practice. CRC Press USA. pp 36-45.
  • Sutton A & Watson T (2011) Electrophysical Agents in Physiotherapy. In: Diagnosis and Management of Lameness in the Horse. 2nd edn. Eds: Ross M W & Dyson S J. Elsevier Saunders, USA. pp 901-907.
  • Gaynor J & Muir W (2009) Handbook of Veterinary Pain Management. 2nd ed. Mosby, USA. pp 83-99.
  • Millis D L, Levine D & Taylor R A (2004) Canine Rehabilitation and Physical Therapy. 2nd edn. Saunders, USA. pp 213-222.
  • Baxter G D (2002) Low-Intensity Laser Therapy. In: Electrotherapy: Evidence-Based Practice. Eds: Kitchen S & Bazin S. Churchill Livingstone, UK. pp 171-190.
  • Bromiley M (1993) Equine Injury, Therapy and Rehabilitation. 2nd edn. Blackwell Science, UK. ISBN: 978-0632036080.