Low-Level Laser Therapy (LLLT) / Photobiomodulation Therapy: Uses, Benefits, Safety and What the Evidence Says
Low-Level Laser Therapy (LLLT), now commonly referred to as Photobiomodulation Therapy (PBM or PBMT), is a non-invasive physiotherapy modality that uses specific wavelengths of red or near-infrared light to influence biological tissues.
It is used in rehabilitation and pain management for a range of musculoskeletal and other conditions. Unlike therapeutic ultrasound, PBM does not use sound waves, and unlike TENS, it does not deliver an electrical current through the skin.
Research into photobiomodulation has expanded considerably, but the evidence is not equally strong for every condition. Recent systematic reviews suggest potential benefits for pain and function in selected musculoskeletal disorders, while considerable uncertainty remains around optimal dosage, wavelength, treatment frequency and long-term effects. (PubMed)
This article explains what PBM is, how it may work, where it may be useful, its potential benefits and limitations, and what current research tells us.
What Is Photobiomodulation Therapy?
Photobiomodulation is the application of non-ionizing light to biological tissue with the intention of producing a therapeutic effect.
Historically, the treatment was commonly called:
Low-Level Laser Therapy (LLLT)
Low-Level Light Therapy
Cold Laser Therapy
Low-Power Laser Therapy
The term photobiomodulation is now increasingly used because modern devices may use either lasers or light-emitting diodes (LEDs).
Depending on the device, PBM may use red light, near-infrared light, or combinations of wavelengths.
The treatment is generally non-invasive and does not normally cause the tissue heating associated with surgical or high-powered lasers.
How Does Photobiomodulation Work?
The exact biological mechanisms of PBM are still being investigated.
One proposed mechanism involves the interaction of light with cellular chromophores, particularly structures associated with mitochondrial function.
Researchers have proposed that PBM may influence:
Cellular energy metabolism
Mitochondrial activity
Nitric oxide signaling
Oxidative stress
Inflammatory signaling
Cellular proliferation and repair processes
Pain-related neural activity
These biological effects provide a plausible explanation for why PBM might influence pain or tissue function.
However, it is important to distinguish biological plausibility from proven clinical effectiveness.
A mechanism observed in laboratory research does not automatically mean that a patient with a particular musculoskeletal condition will experience a clinically meaningful improvement.
What Is the Difference Between LLLT and PBM?
For most physiotherapy discussions, LLLT and PBM refer to closely related treatment concepts.
LLLT traditionally emphasizes the use of low-level laser devices.
PBM is a broader term that includes therapeutic use of appropriate red or near-infrared light delivered by lasers or LEDs.
Therefore, you may see scientific papers using LLLT while newer clinical literature uses PBM or PBMT.
What Does the Research Say?
The overall evidence is promising but heterogeneous.
A 2025 systematic review of laser therapies for orthopedic pain concluded that LLLT and high-intensity laser therapy have potential analgesic effects, but the clinical evidence remains heterogeneous and fragmented. (PubMed)
An important reason for this variability is that PBM is not a single standardized treatment.
Studies can differ in:
Wavelength
Power
Energy density
Irradiance
Treatment time
Number of treatment points
Frequency of treatment
Total treatment dose
Whether PBM is combined with exercise or another treatment
Consequently, a positive result from one PBM protocol cannot necessarily be applied to every laser or LED device.
PBM for Knee Osteoarthritis
Knee osteoarthritis is one of the better-studied musculoskeletal applications of PBM.
A 2024 systematic review and meta-analysis specifically evaluated PBM for pain and disability in people with knee osteoarthritis. The review found evidence of improvement in pain and disability, although the authors emphasized the importance of treatment parameters and the variability between studies. (PubMed)
This suggests that PBM may have a role as an adjunctive treatment for some people with knee osteoarthritis.
However, PBM should not be described as reversing osteoarthritis or rebuilding damaged cartilage.
Osteoarthritis is a complex joint condition, and appropriate management may include:
Exercise
Strength training
Weight management when appropriate
Education
Activity modification
Pain-management strategies
Other evidence-based interventions
PBM may be considered alongside these approaches rather than as a replacement for them.
PBM for Patellofemoral Pain
Recent evidence has also examined PBM in people with patellofemoral pain syndrome.
A 2025 systematic review and meta-analysis included eight trials involving 340 participants. The analysis found statistically significant improvements in pain and function with PBM, but substantial heterogeneity was present and the certainty of evidence was rated very low because of study limitations, imprecision and inconsistency. (PubMed)
This is a good example of how evidence should be interpreted.
The results are encouraging, but low-certainty evidence means we should remain cautious about claiming that PBM is definitively effective for every patient with patellofemoral pain.
PBM for Tendon and Other Musculoskeletal Problems
PBM has been studied in a variety of musculoskeletal disorders, including tendon-related conditions and other orthopedic pain problems.
The overall literature suggests potential pain-relieving effects, but results differ between diagnoses and protocols.
A 2025 systematic review comparing laser therapies with extracorporeal shockwave therapy across musculoskeletal disorders found no clear major difference between LLLT/HILT and shockwave therapy for several outcomes, although the certainty of evidence ranged from very low to moderate. (PubMed)
This reinforces the idea that PBM should be selected according to the individual clinical situation rather than assuming one modality is universally superior.
PBM and Sports Injuries
Photobiomodulation has attracted interest in sports rehabilitation because of its proposed effects on pain and muscle recovery.
A 2024 systematic review and meta-analysis specifically examined PBM for pain and return to play in injured athletes. The research assessed randomized controlled trials involving athletes with musculoskeletal injuries. (PubMed)
The evidence suggests potential benefits, but the question of whether PBM consistently allows athletes to return to sport faster remains less certain than the question of whether it can influence pain.
Therefore, PBM should not be marketed as a guaranteed method for accelerating return to sport.
A return-to-play decision should consider:
Pain
Strength
Range of motion
Tissue capacity
Sport-specific function
Training tolerance
Injury characteristics
PBM for Temporomandibular Disorders
PBM has also been investigated outside conventional orthopedic physiotherapy.
A systematic review and meta-analysis comparing LLLT with TENS and therapeutic ultrasound for temporomandibular disorders found evidence favoring LLLT for some pain and mouth-opening outcomes. (PubMed)
However, this evidence should be interpreted within the specific context of temporomandibular disorders and should not automatically be generalized to every type of musculoskeletal pain.
How Is PBM Applied?
A typical treatment may involve:
Assessment of the patient's diagnosis and treatment goals.
Selection of an appropriate wavelength and treatment protocol.
Positioning the patient comfortably.
Placement of the laser or LED applicator over the target area.
Delivery of the predetermined dose.
Monitoring the patient's response.
Reassessment of pain, movement or function where appropriate.
The applicator may be held directly against the skin or positioned close to it, depending on the device and protocol.
Treatment is usually painless.
Some patients may feel little or no sensation during the procedure.
Does PBM Feel Hot?
Generally, therapeutic PBM is not intended to produce substantial heating.
Patients may feel:
Nothing noticeable
Mild warmth
A slight sensation at the treatment site
The sensation depends on the device, wavelength, power and treatment protocol.
PBM should not be confused with high-powered surgical laser procedures, which have very different purposes and tissue effects.
Potential Benefits of PBM
Depending on the condition and treatment protocol, potential benefits may include:
Pain reduction
Pain reduction is one of the most commonly investigated outcomes.
Recent evidence supports potential improvements in pain for selected musculoskeletal conditions, including knee osteoarthritis and patellofemoral pain. (PubMed)
Improved function
Some clinical trials and meta-analyses report improvements in functional outcomes.
However, functional improvements are generally less consistent than pain outcomes, and evidence quality varies.
Non-invasive treatment
PBM does not require injections or surgical intervention.
Potential adjunct to exercise
If PBM reduces symptoms sufficiently to make movement more comfortable, it may potentially be incorporated alongside therapeutic exercise.
Generally good tolerability
PBM has generally demonstrated a favorable safety profile in clinical research when appropriate parameters are used. A 2025 evidence-based consensus reported PBM as a safe treatment modality for adults for several established clinical applications. (PubMed)
Does PBM Actually “Heal” Tissue?
This is one of the most commonly misunderstood aspects of laser therapy.
Laboratory research has identified biological effects associated with PBM, and clinical studies have investigated wound healing, pain, inflammation and tissue recovery.
However, it is too broad to say:
“Laser therapy heals all damaged tissues.”
The clinical evidence depends heavily on:
Tissue type
Diagnosis
Injury severity
Wavelength
Dose
Treatment frequency
Timing
Patient characteristics
Therefore, claims about accelerated tissue healing should be linked to a specific condition and supported by appropriate clinical evidence.
PBM and Wound Healing
PBM has also been investigated for wounds and ulcers.
A 2025 international evidence-based consensus identified PBM as an effective treatment option for several specific applications, including wound ulcers from multiple causes, pressure ulcers, and pain associated with diabetic foot ulcers. (PubMed)
This is different from saying that PBM is a universal wound-healing treatment.
Wound care should remain diagnosis-specific and may require:
Infection management
Pressure relief
Vascular assessment
Appropriate dressings
Nutrition management
Blood-glucose management
Debridement when indicated
Specialist medical care
PBM, where appropriate, should complement rather than replace essential wound management.
PBM and Cancer: Is It Safe?
This subject requires particular care.
PBM has been used in oncology supportive care, including treatment-related complications such as oral mucositis and some forms of lymphedema.
A systematic review of PBM used for cancer-treatment toxicities found that most included studies reported no side effects and did not identify evidence of tumor-safety problems in the clinical literature reviewed. (PubMed)
A separate systematic review of oncology PBM research similarly reported that clinical and in-vivo evidence available at the time did not demonstrate a clear increase in tumor growth or recurrence. (PubMed)
Nevertheless, PBM should not be applied directly over known or suspected malignant tissue without appropriate specialist guidance.
Patients with active cancer should discuss PBM with their oncology team and treating clinician rather than relying on general safety claims.
Contraindications and Precautions
PBM is generally well tolerated, but appropriate precautions are essential.
Particular caution is appropriate with:
Known or suspected malignancy in the treatment area
Direct exposure to the eyes
Photosensitive conditions
Photosensitizing medications
Pregnancy, depending on treatment area and clinical circumstances
Areas with altered sensation or other conditions requiring individualized assessment
Recent procedures or wounds requiring specialist management
The exact precautions depend on the device, wavelength, treatment dose and treatment area.
Eye Safety
Eye protection is particularly important with therapeutic lasers.
Direct exposure to laser light can injure the eyes, especially with wavelengths that are not easily detected or with higher-powered devices.
Patients and clinicians should follow the manufacturer's safety instructions and use appropriate protective eyewear whenever required.
The laser applicator should never be intentionally directed toward the eyes.
Is PBM Safe?
Overall, PBM has a favorable safety profile when used appropriately.
The evidence-based consensus published in 2025 concluded that PBM is a safe treatment modality for adults across several established clinical applications. (PubMed)
However, “safe” does not mean “risk-free under every circumstance.”
Safety depends on:
Correct device selection
Appropriate wavelength
Appropriate dose
Correct treatment location
Eye protection
Patient screening
Proper clinical technique
Incorrect use of a device can produce unnecessary exposure or injury.
Why Does Dosage Matter So Much?
One of the biggest challenges in PBM research is dose standardization.
Two studies may both claim to investigate “low-level laser therapy” while using very different:
Wavelengths
Power outputs
Energy densities
Treatment times
Treatment frequencies
Number of treatment points
Consequently, the results cannot always be directly compared.
This is one reason why clinicians should not simply copy a protocol from one study and assume that it is appropriate for every patient.
Can More Laser Energy Produce Better Results?
Not necessarily.
PBM appears to have a dose-dependent relationship in which both insufficient and excessive doses may produce less desirable effects.
This means more is not automatically better.
The goal is to use a treatment dose supported by evidence for the specific condition and device.
Recent evidence-based consensus work has emphasized the importance of standardized PBM parameters and appropriate dosing. (PubMed)
PBM vs. High-Intensity Laser Therapy
Both treatments involve therapeutic light, but they are not identical.
LLLT/PBM generally refers to lower-intensity light-based treatment designed primarily for photobiomodulatory effects.
High-Intensity Laser Therapy (HILT) uses substantially higher laser power and has different treatment characteristics.
A 2026 systematic review and network meta-analysis comparing HILT and LLLT found that HILT produced statistically greater pain reductions than LLLT in some comparisons, but the differences were generally modest and the certainty of evidence was predominantly very low. Evidence for disability and range of motion remained limited. (PubMed)
Therefore, it would be inappropriate to claim that HILT is universally better than LLLT.
They should be regarded as related but distinct modalities.
PBM vs. Exercise
PBM and exercise have different purposes.
PBM is primarily a passive modality that may influence pain and other biological processes.
Exercise can improve:
Strength
Mobility
Cardiovascular capacity
Balance
Physical function
Load tolerance
Confidence with movement
For many musculoskeletal conditions, exercise remains an important component of rehabilitation.
PBM may sometimes be used to help manage symptoms while a patient participates in an active rehabilitation programme.
Common Myths About Low-Level Laser Therapy
Myth 1: “Laser therapy works for every injury.”
Reality: Evidence varies substantially by diagnosis and treatment protocol.
Myth 2: “More laser energy always means better results.”
Reality: PBM dosage must be appropriate. More energy is not automatically more effective.
Myth 3: “PBM permanently fixes pain.”
Reality: Evidence is stronger for symptom improvement in selected conditions than for permanent correction of an underlying disorder.
Myth 4: “Laser therapy replaces exercise.”
Reality: PBM is generally best considered an adjunct rather than a replacement for appropriate active rehabilitation.
Myth 5: “All laser machines provide the same treatment.”
Reality: Devices can differ considerably in wavelength, power, dose and delivery method.
Myth 6: “If PBM has biological effects, it must improve clinical outcomes.”
Reality: Biological mechanisms and meaningful patient outcomes are different questions. Clinical effectiveness needs to be demonstrated in appropriate trials.
Frequently Asked Questions
What is low-level laser therapy?
LLLT is a non-invasive treatment using relatively low-intensity red or near-infrared light to produce photobiomodulatory effects in tissue.
Is LLLT the same as photobiomodulation?
The terms are closely related. Photobiomodulation is the broader modern term and includes therapeutic light delivered by both lasers and LEDs.
Is photobiomodulation painful?
Generally, no. Most patients experience little or no sensation, although mild warmth may occur depending on the device.
How many PBM sessions are required?
There is no universal number. Treatment frequency and duration depend on the diagnosis, device, dosage and clinical response.
Can PBM reduce pain?
Evidence suggests that it can reduce pain in some conditions, including certain knee and patellofemoral pain populations. However, results vary and evidence certainty is not uniformly high. (PubMed)
Can PBM help knee osteoarthritis?
Recent systematic-review evidence suggests improvements in pain and disability in people with knee osteoarthritis, although treatment protocols and study quality vary. (PubMed)
Can PBM speed up sports recovery?
PBM has been investigated for pain and recovery in injured athletes, but evidence is not strong enough to guarantee a faster return to sport. (PubMed)
Is PBM safe?
When appropriately applied, PBM generally has a favorable safety profile. However, eye protection and appropriate patient screening remain important. (PubMed)
Can people with cancer receive PBM?
PBM is used in some oncology supportive-care applications, but treatment should be coordinated with the appropriate medical team, particularly when active or suspected cancer is present. (PubMed)
Evidence-Based Takeaway
Photobiomodulation is a promising physiotherapy modality, but the evidence should be interpreted condition by condition.
Current research indicates:
Knee osteoarthritis: systematic-review evidence supports potential improvements in pain and disability. (PubMed)
Patellofemoral pain: recent meta-analysis found improvements in pain and function, but the certainty of evidence was very low. (PubMed)
Musculoskeletal pain generally: evidence is promising but heterogeneous, with major differences between treatment protocols. (PubMed)
Sports injuries: PBM may influence pain, but evidence for faster return to sport is less certain. (PubMed)
Wounds and selected oncology-related complications: PBM has established or promising applications in specific circumstances, rather than as a universal treatment. (PubMed)
Safety: PBM generally appears well tolerated when appropriately applied, but eye safety, patient selection and treatment parameters are important. (PubMed)
Final Thoughts
Low-Level Laser Therapy, or Photobiomodulation Therapy, has moved from being a relatively specialized modality to a widely researched treatment approach in rehabilitation.
The evidence is encouraging, particularly for pain reduction in selected musculoskeletal conditions, but it is not strong enough to justify broad claims that PBM heals every injury or works equally well for every patient.
The most evidence-based approach is to use PBM selectively, with an appropriate dose and treatment protocol, while integrating it into a broader rehabilitation programme when indicated.
For clinicians, the important question is not simply:
“Does laser therapy work?”
It is:
“For this diagnosis, with this treatment goal and this PBM protocol, is there sufficient evidence that the expected benefit justifies using it as part of the patient's rehabilitation?”
That approach keeps photobiomodulation clinically useful while avoiding exaggerated claims.
Selected References
Oliveira S, Andrade R, Valente C, et al. Effectiveness of Photobiomodulation in Reducing Pain and Disability in Patients With Knee Osteoarthritis: A Systematic Review With Meta-Analysis. Physical Therapy. 2024. (PubMed)
Alayat MS, et al. The Effectiveness of Photobiomodulation Therapy on Pain and Function in Patients with Patellofemoral Pain Syndrome—A Systematic Review and Meta-Analysis. Journal of Clinical Medicine. 2025. (PubMed)
High- and Low-Level Laser Therapy for the Treatment of Orthopedic Pain: A Systematic Review. 2025. (PubMed)
Morgan RM, et al. Effects of Photobiomodulation on Pain and Return to Play of Injured Athletes: A Systematic Review and Meta-analysis. Journal of Strength and Conditioning Research. 2024. (PubMed)
Evidence-based consensus on the clinical application of photobiomodulation. 2025. (PubMed)
Extracorporeal Shock Wave Therapy versus laser therapy in treating musculoskeletal disorders: a systematic review and meta-analysis. 2025. (PubMed)
Paglioni MD, et al. Tumor safety and side effects of photobiomodulation therapy used for prevention and management of cancer treatment toxicities: A systematic review. Oral Oncology. 2019. (PubMed)
