Laser Therapy Basics

Originally posted to The Smart Chiropractor blog

You might have seen the ads and heard others mention using light for pain relief and healing. If you read this recent TSC blog, you noticed that laser therapy was recommended in the clinical practice guidelines for chronic neck and lower back pain. But is laser therapy truly a beneficial modality? How does non-invasive light do anything to the tissues? Is it just a fancy placebo?

Let’s define laser therapy quickly. Laser therapy is the use of light to produce a specific stimulatory effect on biological tissues, usually repair, regeneration, and pain reduction. Using laser and LED light to stimulate the body’s healing mechanisms is now termed “photobiomodulation,” but for this post I’m going to mostly use the much sexier term “laser therapy.” Laser therapy has been studied since the 1960s, when a Hungarian surgeon named Endre Mester accidentally found that red laser stimulated faster hair growth in mice. Since then, over 4000 studies have been conducted on hundreds of conditions (nearly 400 studies were published in 2020 alone). Overwhelmingly, the studies demonstrate excellent safety, and in many cases, good effects on painful conditions. Now I’ll get back to this at the end, but first you need to know how laser therapy works.

For light to have an effect on tissues, you need 3 things: absorption of light energy by critical cellular components, penetration of light to the depth of the tissues to be effected, and an effective dose delivered to that depth. This is a bit complex, so let’s break these down one at a time.



Light is absorbed by colored matter that matches the light’s wavelength. Think about wearing a dark shirt outside on a sunny day- you’ll get much warmer than you would with a light colored shirt because the dark material absorbs the sun’s UV and far infrared waves more easily. Wavelengths in the 640-1100nm spectrum (visible red through near-infrared) are absorbed by “colored” chromophores in human cells. Two of these chromophores are cytochrome C oxidase and mitochondrial-bound water molecules, important components in the mitochondrial production of ATP. When CCO and bound water absorb this near-infrared light, they change conformation and position, which increases the rate of ATP formation.

This process also releases limited amounts of nitric oxide (NO) and reactive oxygen species (ROS), which activate transcription factors for growth factor and mediator proteins involved in wound healing. NO also causes vasodilation that improves transport of oxygen and immune cells to the tissue leading to enhanced cell repair. Red and infrared light enhances phagocytosis, angiogenesis, collagen synthesis, keratinocyte and fibroblast proliferation. Laser therapy-induced changes in blood flow and microcirculation promote healing by controlling ischemia, hypoxia, and edema after injury and creating a favorable environment for biological repair after musculoskeletal injury.


Most people don’t really think light can travel through the tissues, but the right kind of light definitely can. Think about shining a flashlight through one side of your hand and seeing your hand glow red- that’s an example of light penetrating the tissues and even coming out the other side. Near-infrared light at 800-1100nm can actually go quite deep into the tissues, even going right through bone! Good penetration of light allows the absorption of photons in deep tissue injuries, and as we saw above, these wavelengths produce multiple beneficial cellular effects. One thing before we move on- even with good penetration, light is absorbed and diffused into the tissues and you get less and less light the deeper you go.


The right dose of light is the third important factor. Take exercise dosing as an example. Working out too briefly with minimal exertion will get you almost no results, but going too hard for too long simply results in more soreness and less benefit. Laser dose is similar in that doing too much or too little will result in minimal results. Laser dose is measured in Joules and most experts have settled on proper dosage of laser being 4-10J/cm2, meaning that if you have a 10 x 10 cm area to treat, your total dose should be 400-1000 Joules total. This is something your laser device should show you.

Now the difficulty with proper dosing comes about when you start thinking about the depth of the tissues you want to treat. Superficial painful wound? 4 J/cm2 should work well. What about a lumbar disc? Or the hip joint? You’ll need to deliver 4-10 J/cm2 to that depth! That means you can no longer simply look at total superficial area for dose calculation. You’ll need much higher amounts of light to get effective doses that deep. But relax, most high-end lasers will have presets that do a lot of the work for you.


Laser Types

Laser devices are divided into classes based on their power output. There are two main types that you’ll find in a PT or chiropractic office: Class 3 and Class 4 units, with class 3 machines producing 0.5 watts or less, and class 4 lasers producing more than 0.5 watts. Both classes of therapy lasers are safe to operate. The main difference between the two classes is that class 4 units deliver their doses faster than class 3 machines do. Quick example- delivering 400 J with a 0.5W class 3 machine will take more than 13 minutes, while a 5W class 4 machine will take less than 2 minutes.

This higher power is important when treating injuries to deeper tissues such as ligaments, muscles, tendons, and cartilage. Beam intensities greater than 1W greatly improve light transmission through soft tissues when compared with lower beam intensities. Several published reports have questioned the ability of low-power lasers to effectively transmit energy beyond the skin into deep tissues.

Class IV laser therapy

Prove it!

I talked about evidence for the effectiveness of laser therapy at the top, and I won’t leave you hanging. Here’s just a few quotes I picked out. For a complete database of research click here.

  • Neuropathy- Laser therapy “has beneficial effects on the recovery of nerve lesion, especially when related to a faster regeneration and functional improvement.”

  • Headaches- Laser for chronic migraines is just as effective as botox injections while being cheaper and reducing sleep disturbance better.

  • Musculoskeletal conditions- 94% of articles included in this study on class 4 laser for musculoskeletal pain revealed positive effects.

  • Athletic performance- Light therapy produces better muscle recovery and strength gains post-exercise than ice does, while still reducing soreness.

  • Complex diseases- Light therapy can raise the standard of care and improve the quality of life of patients for a fraction of the cost of many current approaches. “Progress will lead to the imminent inception of light therapy as a mainstream treatment for multiple complex diseases...It is time to begin considering light therapy as a potential drug equivalent.”


So, how does laser therapy work? Specific colors of light induce faster ATP production, which also produces increased NO and ROS, causing vasodilation for improved blood flow and cellular repair. This means that laser therapy, when used with the right equipment and techniques, can produce good results in dozens of conditions, from neuropathy to arthritis to acute injuries. Because you’re simply accelerating the body’s natural healing processes, this perfectly aligns with the drug-free natural healing philosophy that most of us chiropractors operate with. Light therapy reduces pain and so the consumption of pain killers and anti-inflammatory pharmaceuticals with their long-term side-effects can be reduced.

Laser therapy enables non-invasive practitioners to amplify patient results, and of course, patient results drive patient referrals. Laser also provides an additional revenue stream that in many cases is reimbursed by insurance companies, and is legal for chiropractors to operate in all 50 states. Many other providers can also provide photobiomodulation treatments. Lastly, by adding laser therapy to their practice, providers expand the spectrum of conditions that can be addressed through natural, drug-free methods.

Class IV Laser Treatment
Class 4 Laser Therapy

Look, simply buying a laser won’t guarantee patient results and financial success. Along with the right laser equipment, you also need to have the right training and protocols, and figuring all that out can be daunting. I founded Laser Therapy Institute to provide that training because I believe laser is a great tool for non-invasive practitioners like chiropractors and physical therapists. For more information on how laser works, check out our website or listen to the podcast. Need training on laser techniques, guidance on finding the right equipment, or help implementing laser in your clinic? Check out our full suite of resources or schedule a demo here!