Published on December 16, 2025
Why Most Laser Therapy Research Got It Wrong
Reviewed by: Dr. David Drazic, D.C.
Reviewed for: clinical accuracy, patient safety, scope-of-practice accuracy, and service appropriateness
Laser therapy is one of those treatments where two devices can share the same name while delivering very different interventions.
One system may operate below half a watt. Another can deliver several watts. Wavelengths vary. Treatment times vary. Energy density varies. Some lasers are pulsed. Others are continuous.
That creates a legitimate problem when people ask a simple question:
“Does laser therapy work?”
The answer depends partly on which laser, at what dose, for which condition.
High-intensity Class IV laser therapy has produced encouraging results for several musculoskeletal conditions. But the evidence does not support writing off low-level laser research as worthless or treating high power alone as proof of superior healing.
What Makes A Class IV Laser Different?
Laser classifications are commonly misunderstood.
“Class IV” is primarily a laser-safety classification related to accessible power and potential exposure hazards. It does not mean “Level 4 effectiveness.”
The FDA explains that higher laser classes generally involve greater power and a greater potential for serious eye or skin injury if the beam is used improperly. (U.S. Food and Drug Administration)
Therapeutically, higher output has one practical advantage.
It allows clinicians to deliver greater amounts of optical energy relatively quickly.
That can be particularly useful when treating a large area or trying to deliver a selected dose to deeper tissues.
What it does not mean is that every Class IV device produces better clinical outcomes than every lower-powered device.
Power Is Only One Part Of Laser Dose
Laser treatment involves several interacting parameters.
Power is measured in watts.
Total energy is measured in joules.
Energy density, or fluence, describes how much energy is delivered over a particular area.
Then there is wavelength, irradiance, pulse structure, treatment time, and tissue characteristics.
That means two clinicians can both say they used “Class IV laser therapy” while delivering substantially different treatments.
This helps explain why studies frequently disagree.
The research is not simply comparing strong lasers with weak lasers.
It is often comparing completely different optical doses.
The Study That Put 10-Watt Laser Therapy On The Map
A frequently cited Class IV study examined chronic lateral epicondylitis, commonly known as tennis elbow.
Researchers used a dual-wavelength 810/980 nm system capable of 10 watts.
Previous research referenced by the investigators had commonly used devices below 0.5 watts, so the study deliberately examined whether a higher-power treatment could produce meaningful clinical results. (PubMed)
Participants received eight treatments over 18 days.
At 3, 6, and 12 months, the laser group demonstrated improvements in grip strength, function, and pain during a resisted middle-finger extension test.
At 12 months:
- Grip strength improved approximately 66%
- Function improved approximately 82%
- Pain during the resisted test declined approximately 100%
Those numbers sound extraordinary. (PubMed)
There is an important limitation.
The study included only 16 people.
Why The Tennis-Elbow Results Need Context
A randomized, double-blind, sham-controlled study is a strong design.
Sixteen participants is still an extremely small sample.
The “100% pain reduction” also represented improvement from baseline during a specific provocative test. It was not evidence that every patient had absolutely no elbow pain under every circumstance.
The sham group improved substantially as well.
By 12 months, sham participants demonstrated:
- Approximately 13% greater strength
- Approximately 52% greater function
- Approximately 76% less pain during the resisted test
(PubMed)
The authors therefore did not conclude that the treatment was a proven cure.
They concluded that the promising findings warranted further study.
That is the appropriate way to use this trial.
What New Research Says About High-Power Versus Low-Power Laser
We now have considerably more evidence than existed when that trial was published.
A 2026 systematic review directly compared high-intensity laser therapy with low-level laser therapy across musculoskeletal conditions.
Some analyses favoured HILT for pain reduction.
But the average differences were generally modest and frequently below established minimal clinically important difference thresholds. Disability and range-of-motion findings were too heterogeneous to support firm conclusions.
The certainty of evidence was predominantly very low. (PubMed)
The conclusion was not that low-level lasers had failed.
The researchers stated that both HILT and LLLT could be considered therapeutic options and that HILT should be used cautiously as part of multimodal rehabilitation.
Does Class IV Laser Work For Musculoskeletal Pain?
There is reasonable evidence that high-intensity laser therapy can improve some pain and functional outcomes.
A systematic review containing 48 randomized trials found HILT reduced pain and improved function across a range of musculoskeletal disorders.
The benefit was larger when HILT was compared with inactive controls than when it was compared with other conservative treatments. Evidence quality was low for pain and moderate for function. (PubMed)
Another umbrella review evaluated 20 systematic reviews involving conditions including:
- Knee osteoarthritis
- Frozen shoulder
- Low back pain
- Neck pain
- Lateral epicondylalgia
- Plantar fasciitis
- Myofascial pain
The authors found encouraging analgesic effects but rated the methodological quality of the available systematic reviews as generally low to critically low. (PubMed)
That makes high-intensity laser a legitimate conservative modality.
It does not make it a universal standard of care.
What About Conditions Where HILT Has Not Shown Clear Superiority?
Not every recent review favours high-intensity laser.
A 2025 systematic review of HILT for De Quervain’s tenosynovitis found no statistically significant advantage in pain or disability compared with conventional treatments such as splinting or splinting with exercise. (PubMed)
This is exactly why laser therapy should be discussed condition by condition.
A treatment can have encouraging evidence in one musculoskeletal problem without automatically being effective for every tendon, joint, or nerve condition.
Does More Power Make The Laser Reach Deeper?
Power can influence how efficiently energy is delivered.
It is still inaccurate to imagine that a 10-watt beam simply travels deep into the body while a 500-milliwatt beam stops at the skin.
Biological tissue absorbs and scatters light.
Penetration depends on:
- Wavelength
- Tissue type
- Skin pigmentation
- Blood and water content
- Beam characteristics
- Target depth
- Irradiance
- Treatment technique
Higher output may allow a clinically useful dose to be delivered more quickly and may improve the amount of energy available to deeper tissues.
But the relationship between surface wattage, penetration depth, and clinical benefit is not one-to-one.
What Is Photobiomodulation Actually Doing?
The biological effects of therapeutic red and near-infrared light are usually discussed under the term photobiomodulation.
Unlike surgical lasers, the intention is not to destroy or remove tissue.
Researchers have proposed several cellular mechanisms.
One leading model involves cytochrome c oxidase in mitochondria. Photons may influence the interaction between cytochrome c oxidase and nitric oxide, potentially increasing electron transport, mitochondrial membrane potential, ATP production, and downstream cellular signalling. (PubMed Central (PMC))
Other proposed mechanisms involve light-sensitive ion channels and changes in:
- Calcium signalling
- Reactive oxygen species
- Nitric oxide
- Gene transcription
- Protein production
- Cell migration and proliferation
- Inflammatory signalling
These are plausible and actively studied mechanisms.
They are not a complete, settled explanation for every clinical benefit attributed to photobiomodulation.
Does Laser Therapy Create “Actual Healing”?
This phrase needs definition.
If a therapy reduces pain while function improves, that is clinically useful even if we cannot prove a tendon has regenerated structurally.
Laboratory studies suggest photobiomodulation can affect cellular pathways involved in tissue repair, including protein synthesis and inflammatory signalling. (PubMed Central (PMC))
What we cannot infer automatically is:
laser exposure → increased ATP → complete tissue regeneration.
Human tendon, cartilage, muscle, nerve, and joint conditions all behave differently.
Clinical healing should be evaluated through meaningful outcomes such as:
- Pain
- Strength
- Range of motion
- Functional ability
- Return to work or sport
- Recurrence
Mechanistic research explains why a treatment might work.
Clinical trials tell us whether patients actually benefit.
The Cortisone Comparison Needs More Nuance
Corticosteroid injections are sometimes presented as the opposite of laser therapy.
Cortisone suppresses inflammation, the argument goes, while laser promotes genuine healing.
Clinical medicine is not that simple.
Corticosteroid injections can be useful for certain conditions and less attractive for others.
For Tennis Elbow
There is good reason to be cautious.
A large randomized trial found that people receiving corticosteroid injections for chronic lateral epicondylalgia had worse one-year recovery and a much higher recurrence rate than those receiving placebo injections.
Recurrence reached 54% after corticosteroid injection compared with 12% following placebo. (PubMed)
A systematic review found a similar pattern: substantial short-term pain relief from corticosteroid injection followed by worse intermediate and long-term outcomes for lateral epicondylalgia. (PubMed)
For this particular condition, a discussion about alternatives is reasonable.
Can Cortisone Harm Tendons?
Laboratory and animal evidence demonstrates legitimate biological concerns.
A systematic review found that local glucocorticoid exposure can reduce fibroblast viability and proliferation, decrease collagen synthesis, disrupt collagen organization, and reduce tendon mechanical properties. (PubMed)
Rotator-cuff research has similarly identified reduced collagen and tendon-cell viability and increased apoptosis after corticosteroid exposure. Effects appear related to dose and frequency and may be transient. (PubMed)
That does not justify saying corticosteroids inevitably “necrose tissue.”
There is a difference between measurable adverse cellular effects and claiming that an appropriately selected injection destroys a patient’s joint.
Steroid Injections Can Also Be Effective
De Quervain’s tenosynovitis provides a clear counterexample.
A 2024 meta-analysis involving 16 studies and 1,206 patients found corticosteroid injection was more successful than immobilization, while combining injection and immobilization produced the best outcomes. (PubMed)
The right question is therefore not:
“Laser or cortisone, which one actually heals?”
It is:
“What condition are we treating, and what does the evidence support for this patient?”
What About Repeated Knee Injections?
Repeated intra-articular corticosteroid injections deserve separate consideration.
A two-year randomized clinical trial in people with knee osteoarthritis found triamcinolone injections every three months resulted in greater cartilage loss than saline and no significant difference in pain. (PubMed)
An older randomized trial using repeated injections over two years found no significant increase in radiographic joint-space loss and reported some symptom benefit. (PubMed)
The evidence is therefore not captured accurately by saying cortisone either “only reduces inflammation” or “destroys the joint.”
Dose, frequency, diagnosis, injection location, and treatment goals all matter.
Can Class IV Laser Help Knee Arthritis?
High-intensity laser therapy has been studied for knee osteoarthritis, and several reviews have reported improvements in pain and function.
However, overall methodological quality remains variable, and study protocols differ considerably. (PubMed)
Laser may be used as an adjunct to a broader conservative program.
For knee osteoarthritis, that broader program can still include exercise, strength work, physical activity, weight management where relevant, medication, injections, and orthopaedic consultation depending on disease severity.
A modality should add to appropriate care rather than replace the clinical decision-making around it.
Can Laser Heal A Meniscus And Prevent Surgery?
Current evidence is not strong enough to promise that Class IV laser repairs a torn meniscus or prevents surgery.
Many meniscal problems can already be managed without surgery depending on the type of tear, age, symptoms, mechanical locking, osteoarthritis, physical demands, and response to rehabilitation.
If someone receives laser therapy and ultimately does not need surgery, that individual experience can be meaningful.
It does not establish that laser regenerated the meniscus or that most patients will avoid surgery because of it.
Claims about avoiding surgery require direct comparative evidence.
Class IV Laser At Lakeview Chiropractic & Acupuncture Wellness Centre
Lakeview Chiropractic & Acupuncture Wellness Centre offers Class IV laser therapy as one of its adjunctive treatment modalities for selected musculoskeletal conditions.
The clinic currently uses the treatment for problems including joint and soft-tissue complaints and incorporates it alongside chiropractic care, exercise guidance, interferential therapy, shockwave therapy, acupuncture, or other approaches when appropriate. (Lakeview Chiropractic & Acupuncture)
Dr. David Drazic develops the treatment plan according to the diagnosis and clinical assessment rather than using laser as a universal treatment for pain. (Lakeview Chiropractic & Acupuncture)
That is particularly important given what the research tells us.
A Class IV laser is not automatically the best treatment because of its wattage.
The value comes from selecting an appropriate patient, condition, wavelength, dose, treatment schedule, and broader rehabilitation plan.
Frequently Asked Questions About Class IV Laser Therapy
What Is The Difference Between Class III And Class IV Laser Therapy?
Class designations primarily describe laser-output hazard categories. Class IV systems generally allow greater accessible power than Class III devices and therefore require greater safety precautions. In therapeutic use, higher output can also allow larger doses to be delivered more quickly. (U.S. Food and Drug Administration)
Is Class IV Laser More Effective Than Cold Laser?
Not in every situation. Recent comparisons have shown modest advantages for HILT in some pain outcomes, but overall certainty is low and clinical differences are often small. Both high- and low-intensity photobiomodulation have supportive evidence for selected conditions. (PubMed)
Is Class IV Laser Really A “Cold Laser”?
The terminology is inconsistent. Low-level photobiomodulation is traditionally called cold laser because it produces little meaningful heating. Higher-powered Class IV systems may produce perceptible warmth, so “cold laser” is not a particularly precise technical description.
Does Class IV Laser Reach Deep Tissue?
Near-infrared wavelengths can penetrate into biological tissue, but energy decreases with depth because light is absorbed and scattered. Higher power can make it easier to deliver an adequate treatment dose, but surface wattage does not tell you exactly how much energy reaches a deep tendon or joint.
Does Laser Therapy Increase ATP And Collagen?
Photobiomodulation may influence mitochondrial signalling, ATP production, and pathways related to protein synthesis and tissue repair. These mechanisms are actively researched and should not be interpreted as proof that laser completely regenerates damaged human tissue. (PubMed Central (PMC))
Can Class IV Laser Cure Tennis Elbow?
A very small 10-watt randomized trial reported promising long-term improvements in chronic lateral epicondylitis, but only 16 people participated. The evidence is not strong enough to describe Class IV laser as a cure. (PubMed)
Is Class IV Laser Better Than Cortisone For Tennis Elbow?
Corticosteroid injections have demonstrated poor longer-term outcomes and high recurrence in lateral epicondylalgia. Class IV laser has promising evidence, but direct high-quality comparisons are insufficient to declare one universally superior. (PubMed)
Does Cortisone Destroy Tendons?
Repeated or high-dose corticosteroid exposure can negatively affect tendon cells, collagen synthesis, and mechanical properties. The clinical risk depends on injection site, frequency, dose, and condition. It is inaccurate to say that every corticosteroid injection causes tissue necrosis. (PubMed)
Can Class IV Laser Help Me Avoid Surgery?
Possibly in the sense that successful conservative treatment can sometimes make surgery unnecessary. Current evidence does not support promising that Class IV laser itself prevents surgery or repairs every structural problem that might otherwise require an operation.
Laser Therapy Is Better Understood Through Dose Than Hype
The most useful lesson in the laser literature is that the details matter.
A 10-watt laser and a 300-milliwatt laser are not identical treatments.
Neither should be judged on wattage alone.
High-intensity Class IV laser therapy has encouraging evidence for pain and functional improvement across several musculoskeletal conditions. It may also offer practical advantages when clinicians need to deliver therapeutic energy efficiently.
At the same time, current reviews show considerable variability in treatment protocols and generally limited certainty when HILT is compared directly with other active treatments. (PubMed)
That makes Class IV laser a tool, not a miracle.
If a tendon, joint, or other musculoskeletal problem is continuing to limit work, sport, or everyday activity, Lakeview Chiropractic & Acupuncture Wellness Centre can assess the condition and determine whether Class IV laser therapy, chiropractic care, exercise, shockwave therapy, acupuncture, further investigation, or another treatment strategy is appropriate.
Medical Disclaimer
This article is for educational purposes only and does not replace an individualized examination, diagnosis, or treatment recommendation from a licensed healthcare professional. Class IV laser therapy, corticosteroid injections, rehabilitation, medications, and surgical procedures have different indications, evidence, limitations, and risks depending on the condition. Treatment choices should be made after appropriate clinical assessment.
Sources And Clinical References
Lasers In Surgery And Medicine: The Effectiveness Of Therapeutic Class IV 10-Watt Laser Treatment For Epicondylitis. Small randomized, double-blind sham-controlled trial reporting promising long-term improvements after Class IV laser treatment while involving only 16 participants and calling for additional investigation. (PubMed)
Lasers In Medical Science: High-Intensity Versus Low-Level Laser Therapy In Musculoskeletal Disorders. 2026 systematic review and network meta-analysis finding modest HILT advantages for some pain outcomes but predominantly very low-certainty evidence and limited evidence of meaningful superiority in disability or range of motion. (PubMed)
High-Intensity Laser Therapy For Musculoskeletal Disorders: Systematic Review And Meta-Analysis. Supports possible improvements in pain and function while demonstrating greater effects against inactive controls than against other conservative treatments. (PubMed)
Umbrella Review Of High-Intensity Laser Therapy For Musculoskeletal Pain. Finds favourable results across several musculoskeletal conditions but identifies generally low or critically low methodological quality among existing systematic reviews. (PubMed)
Proposed Mechanisms Of Photobiomodulation Or Low-Level Light Therapy. Reviews proposed mitochondrial, ATP, nitric-oxide, calcium, cell-signalling, inflammatory, and protein-synthesis pathways relevant to photobiomodulation. (PubMed Central (PMC))
JAMA: Corticosteroid Injection, Physiotherapy, Or Both For Lateral Epicondylalgia. Randomized trial supporting poorer one-year recovery and substantially greater recurrence following corticosteroid injection compared with placebo. (PubMed)
British Journal Of Sports Medicine: Risks And Benefits Of Glucocorticoid Treatment For Tendinopathy. Supports adverse cellular and collagen effects of local glucocorticoids on tendon tissue while showing that effects depend on dose, frequency, and experimental context. (PubMed)
FDA: Frequently Asked Questions About Lasers. Clarifies that Class IV is fundamentally a laser hazard and output classification requiring appropriate safety controls rather than a rating of therapeutic effectiveness. (U.S. Food and Drug Administration)