Let There Be Light: Why Laser Therapy Is Evidence-based Medicine

Check out 10 common criticisms of laser therapy heard around the virtual veterinary water cooler and evidence-based responses.

For those who view drugs and surgery as mainstay treatments, laser therapy may seem odd. Nothing is injected, swallowed or even tangible, yet proponents claim that light can help tissue heal and injured nerves regrow. Here are 10 common criticisms heard around the virtual veterinary water cooler and evidence-based responses.

1. “Some studies show that laser therapy does not work.” True.

A number of negative studies on laser therapy have appeared in the medical literature over decades of research. However, several parameters influence outcomes, including wavelength, fluence, irradiance, treatment repetition and timing, as well as pulsing.1

Ineffective doses and lack of laser output testing further muddy the interpretation of outcomes in laser research.2 In order to identify and prevent more methodological flaws in laser research, the World Association for Laser Therapy publishes standards for the design and conduct of clinical studies,3 systematic reviews and meta-analyses.4

2. “Most laser research is of too poor quality to allow interpretation of effectiveness.” False.

Several systematic reviews and meta-analyses (i.e., high grade evidence) have found in favor of laser therapy for various conditions. These include neck pain,5,6 frozen shoulder,7 tennis elbow,8 Achilles tendinitis,9 neurosensory deficit after third molar surgery,10 pain and stiffness from rheumatoid arthritis,11 cancer therapy-induced mucositis,12 stiffness in hand osteoarthritis13 and more.

3. “The price of the laser has little to do with its clinical value.” Yes and no.

One could spend well over 10 grand for a very low-level laser in the milliwatt range or a similar price for one thousands of times more powerful. Veterinarians’ best defense against buying an inadequate machine based on advertising hype is education through channels other than sales staff and their paid lecturers, who may invent or perpetuate unfounded mechanisms of action and clinical outcomes based on little more than a fanciful imagination.

Speakers should be able to point to or produce evidence that backs their claims. A common practice involves making claims for one type of machine but supplying evidence that utilized much different equipment. 

4. “Laser therapy is the latest gimmick from the holistic veterinary community.” False.

Laser therapy has existed for decades and was adopted by human medicine long before it fully emerged as an adjunctive healing technique for animals.  It has gained a foothold in the U.S. and British military, Olympic teams, and pain clinics across the United States and Europe.14

5. “Laser therapy is essentially heat therapy, but much more expensive than a simple hot pack.” Incorrect.

Not all units cause tissue warming; whether a patient perceives heat depends on the wavelength of the light and the power applied. The main effect of laser does not arise from thermal effects, however. Instead, results manifest by dint of a photochemical reaction in tissue called photobiomodulation.

This term refers to the changes that take place after either visible or near infrared (NIR) light enters mitochondria and subsequently induces a variety of physiologic changes. These include upregulation of cellular respiration along with accentuated transcription of stimulatory and protective genes.

Laser therapy affects a plethora of tissues, including neurons. Exciting research on laser therapy and nerve regeneration is showing how low power laser promotes nerve regeneration in corticospinal tract axons, facilitating return of function after acute spinal cord injury in a rat model.15

6. “No guidelines exist for treatment; it’s a veritable free-for-all when it comes to figuring out the right laser dose.” Incorrect.

The World Association of Laser Therapy provides a list of recommended treatment doses for numerous musculoskeletal pain problems.16

The approaches are geared for humans and arise from results of clinical trials or extrapolation of results from studies in nonhumans focused on animal models involving similar pathology. Current recommendations for veterinary patients align closely with these guidelines until evidence from clinical veterinary trials indicates otherwise.

7. “Laser only benefits joints by reducing pain. It does nothing for other aspects of osteoarthritis.” Untrue.

Laser irradiation, especially at 808nm, helps repair injury to cartilage, promote angiogenesis and limit the development of fibrosis in a rodent model of osteoarthritis.17

Laser therapy reduces the total number of leukocytes and neutrophils in the joint cavity of rodents with experimentally induced stifle inflammation. Furthermore, laser irradiation inhibits production of interleukin (IL)-1, IL-6, and prostaglandin E2.18

8. “There is no evidence that Class IV (i.e., higher powered, > 500 mW) therapy lasers do much except treat pain.” False.

A recent study of Class IV laser therapy found that a 3W protocol at 50 percent duty cycle applied to the biceps brachii muscle (360 J) improved circulation to the distal limb, implicating its ability to benefit tissue health through better blood flow.19 With enthusiasm for Class IV lasers growing at a rapid pace, more research is expected in the near future.

9. “The only clinical trials available on laser therapy have been done on humans.” Mostly true, but changing.

Laser therapy clinical trials are taking place or have been recently completed at veterinary colleges such as Colorado State University and the University of Florida. CSU is pursuing a randomized, controlled clinical trial on Class IV laser for snake envenomation in dogs.20

Neurologists at the University of Florida have completed a study applying Class IIIb laser for dogs with intervertebral disk disease.21 Their results showed that after spinal cord injury and surgery, dogs who received laser therapy walked sooner, avoided medical complications and were discharged sooner, resulting in lower costs.  Dr. Tom Schubert, one of the researchers, reported, “The results were so profound that we’re doing this procedure now on all dogs that come to us with this condition.”

10. “Many cannot explain the science behind laser therapy.” Unfortunately, yes.

This does not mean that the science is unavailable. Instead, the rationale behind laser therapy escapes many, even those who use it regularly.

As more veterinary schools adopt laser therapy and teach its basic science to students, growing numbers of practitioners will recognize that laser therapy, when properly applied and appropriately dosed, provides clinically significant benefits and expands our options for delivering compassionate veterinary care with fewer drugs and less surgery.



1. Hashmi JT, Huang Y-Y, Osmani BZ, et al. Role of low-level laser therapy in neurorehabilitation. PM R.  2010;2:S292-S305.

2. Bjordal JM and Baxter GD. Ineffective dose and lack of laser output testing in laser shoulder and neck studies.  Photomed Laser Surg. 2006;24(4):533-534.

3. World Association for Laser Therapy. Consensus agreement on the design and conduct of clinical studies with low level laser therapy and light therapy for musculoskeletal pain and disorders. Obtained on 5/7/12 at /redirect.aspx?location=http://www.walt.nu/images/stories/files/walt_standard_for_conduct_of_randomized_controlled_trials.pdf.

4. World Association for Laser Therapy. Standard for the design and conduct of systematic reviews with low level laser therapy for musculoskeletal pain and disorders. Obtained on 5/7/12 at /redirect.aspx?location=http://www.walt.nu/images/stories/files/walt_standard_for_conduct_of_systematic_reviews_and_meta-analyses.pdf.

5. Chow RT, Johnson MI, Lopes-Martins RAB, et al. Efficacy of low-level laser therapy in the management of neck pain: a systematic review and meta-analysis of randomised placebo or active-treatment controlled trials.  The Lancet. 2009;374(9705):1897-1908.

6. Haldeman S, Carroll L, Cassidy JD, et al. The Bone and Joint Decade 2000-2010 Task Force on Neck Pain and Its Associated Disorders:  Executive Summary. Wpine. 2008;33(4S):S5-S7.

7. Favejee MM, Huisstede BM, Koes BW. Frozen shoulder: the effectiveness of conservative and surgical interventions – systematic review.  Br J Sports Med. 2011;45(1):49-56.

8. Bisset L, Coombes B, and Vicenzino B. Tennis elbow. Clin Evid (Online). 2011;pii:1117.

9. Carcia CR, Martin RL, Houck J, et al. Achilles pain, stiffness, and muscle power deficits: Achilles tendinitis. J Orthop Sports Phys Ther. 2010;40(9):A1-A26.

10. Leung YY, Fung PP, and Cheung LK. Treatment modalities of neurosensory deficit after lower third molar surgery: a systematic review. J Oral Maxillofac Surg. 2012;70(4):768-778.

11. Brosseau L, Welch V, Wells G, et al. Low level laser therapy for osteoarthritis and rheumatoid arthritis:  a metaanalysis. J Rheumatol. 2000;27:1961-1969.

12. Bensadoun R-J and Nair RG. Low-level laser therapy in the prevention and treatment of cancer therapy-induced mucositis: 2012 state of the art based on literature review and meta-analysis. Current Opinion in Oncology. 2012. ISSN: 1040-8746.

13. Ye L, Kalichman L, Spittle A, et al. Effects of rehabilitative interventions on pain, function and physical impairements in people with hand osteoarthritis: a systematic review. Arthritis Research & Therapy.  2011;13:R28.



16. http://www.walt.nu/images/stories/files/Dose_table_780-860nm_for_Low_Level_Laser_Therapy_WALT-2010.pdf

17. da Rosa AS, dos Santos AF, da Silva MM, et al. Effects of low-level laser therapy at wavelengths of 660 and 808 nm in experimental model of osteoarthritis. Photochemistry and Photobiology. 2012;88:161-166.

18. Pallotta RC, Bjordal JM, Frigo L, et al. Infrared (810-nm) low-level laser therapy on rat experimental knee inflammation. Lasers Med Sci. 2012;27:71-78.

19. Larkin K. Limb blood flow after class 4 laser therapy. J Athletic Training. 2012;47(2):178-183.

20. Author’s study.

21. Carey S. Laser therapy shown to benefit dogs with intervertebral disc disease. UF Health Science Center News Communications. Accessed on 5/8/12 at /redirect.aspx?location=http://news.health.ufl.edu/2011/17650/colleges/college-of-veterinary-medicine/laser-therapy-shown-to-benefit-dogs-with-intervertebral-disc-disease/.

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