What Is Class 4 Laser Therapy?
Class 4 laser therapy is a form of photobiomodulation therapy (PBM) that uses therapeutic light to interact with tissues in the body. Unlike a laser pointer or other low-powered laser devices, Class 4 therapeutic lasers can deliver substantially higher power and energy to targeted areas.
In physical therapy, high-intensity laser therapy (HILT) may be used as part of a larger rehabilitation program to help manage pain, support tissue recovery, and improve a patient's ability to participate in therapeutic exercise and movement.
The important distinction is that laser therapy is generally not intended to replace physical therapy exercises, strength training, mobility work, or other active rehabilitation strategies. Instead, it can be used as an adjunct to a comprehensive treatment plan.
Research on high-intensity laser therapy has found improvements in pain and physical function across several musculoskeletal conditions, although the quality of evidence varies between conditions and treatment protocols. A 2023 systematic review and meta-analysis that included 48 randomized controlled trials found that HILT reduced pain and improved functionality in people with musculoskeletal disorders, with low-to-moderate certainty of evidence.
How Does Class 4 Laser Therapy Work?
Photobiomodulation works by delivering specific wavelengths of light to biological tissues. The light can interact with cellular components and influence processes involved in pain, inflammation, circulation, and tissue repair.
The biological response depends on several factors, including:
- Wavelength
- Power
- Energy delivered
- Treatment time
- Treatment area
- Tissue depth
- Pulsed or continuous delivery
- The condition being treated
This is one reason why simply saying that "laser therapy works" does not tell the whole story. The dosage and treatment parameters matter.
A systematic review examining the use of 1064-nm light in photobiomodulation noted that outcomes can vary depending on wavelength, power, beam size, dosage, and delivery method. The ability of light to reach the target tissue is also influenced by absorption and scattering within the body.
For physical therapists, this means treatment should be individualized rather than applying the same laser protocol to every patient.
What Does the Research Say About Pain Relief?
One of the most studied applications of laser therapy is pain management.
A 2023 systematic review and meta-analysis of high-intensity laser therapy included 48 randomized controlled trials involving people with musculoskeletal disorders. Researchers found that HILT was associated with a reduction in pain and improvement in function compared with control interventions. However, the authors rated the quality of evidence as low for pain and moderate for function.
More recent research continues to support the potential role of photobiomodulation for certain musculoskeletal conditions.
For example, a 2024 systematic review and meta-analysis examining photobiomodulation for knee osteoarthritis included 10 studies and 542 participants. The researchers found a statistically significant reduction in pain at rest compared with placebo, although the certainty of evidence was considered very low. The authors concluded that PBM may be useful as a complement to other recommended treatments rather than as a stand-alone treatment.
This distinction is important.
Laser therapy may help reduce symptoms, but reducing pain is only one part of successful rehabilitation. The long-term goal of physical therapy is typically to help patients improve strength, mobility, tolerance to activity, and overall function.
Can Class 4 Laser Therapy Help With Inflammation?
Inflammation is another area of interest in photobiomodulation research.
PBM may influence cellular processes associated with inflammation and tissue recovery. These effects are one reason researchers have investigated laser therapy for a wide range of orthopedic and musculoskeletal conditions.
However, it is important to avoid oversimplifying this process. Laser therapy should not be described as simply "removing inflammation." The body's inflammatory response is complex, and inflammation can be both beneficial and harmful depending on the stage and type of tissue injury.
Current research suggests that photobiomodulation may influence inflammatory and pain-related pathways, but clinical outcomes can vary significantly depending on the condition and treatment parameters.
A 2025 systematic review of randomized controlled trials investigating high- and low-level laser therapy for orthopedic pain found evidence supporting improvements in pain and physical function across several conditions. At the same time, researchers emphasized substantial differences between laser parameters, treatment protocols, and outcome measures.
What About Muscle and Soft Tissue Recovery?
Laser therapy has also been investigated for muscle and soft tissue conditions.
One example is myofascial pain syndrome, which can involve painful and sensitive areas within muscles and surrounding tissues.
A systematic review and meta-analysis of 17 studies involving 944 participants found that photobiomodulation was associated with reduced pain and increased pressure pain thresholds in people with upper trapezius myofascial pain syndrome. The effects appeared stronger when PBM was combined with exercise, although the researchers noted that the overall quality of evidence limited confidence in the findings.
This supports an important concept in physical therapy:
The combination of passive and active treatments may be more useful than relying on a passive modality alone.
Laser therapy may help make movement more comfortable, while therapeutic exercise helps address strength, mobility, capacity, and movement limitations.
Can Laser Therapy Help With Tendon and Foot Conditions?
Researchers have also studied photobiomodulation in conditions such as plantar fasciitis.
A 2023 systematic review and meta-analysis evaluated 19 randomized controlled trials involving 1,089 participants with plantar fasciitis. The researchers found that PBM improved short-term pain intensity, both when used alone and when combined with exercise. PBM combined with exercise also showed benefits during follow-up compared with exercise alone in some analyses.
However, the authors also noted uncertainty regarding improvements in disability and differences between treatment approaches.
This illustrates why evidence-based physical therapy does not simply ask, "Does laser work?"
Instead, clinicians should consider:
Who is the patient?
What condition are we treating?
What laser parameters are being used?
What other treatments are being provided?
What outcome are we trying to improve?
What Does the Research Say About Knee Pain?
Knee osteoarthritis is another area where photobiomodulation has been extensively studied.
The 2024 systematic review mentioned earlier found that PBM reduced pain at rest compared with placebo in patients with knee osteoarthritis. However, the certainty of evidence was very low, meaning researchers have limited confidence in the size and consistency of the effect.
This is an important part of interpreting research.
A study can demonstrate a statistically significant improvement without proving that the treatment will produce the same meaningful result for every patient.
For this reason, laser therapy is best viewed as one potential tool within a broader rehabilitation strategy.
What About Low Back Pain?
The research is not universally positive, and this is important to acknowledge.
A systematic review of 12 randomized controlled trials involving 1,046 participants found that photobiomodulation did not produce clinically important improvements in pain or disability compared with sham treatment in people with nonspecific low back pain. The authors concluded that the evidence did not support PBM for reducing pain and disability in this population.
This is a good example of why evidence-based practice requires more than highlighting studies with positive findings.
The effectiveness of laser therapy appears to depend on the condition, treatment parameters, patient population, and how the therapy is incorporated into rehabilitation.
Can Laser Therapy Be Combined With Exercise?
Yes. In fact, some research suggests that combining photobiomodulation with active rehabilitation may be particularly useful for certain conditions.
A 2026 systematic review and meta-analysis examining photobiomodulation for patellofemoral pain syndrome found that PBM combined with exercise was associated with improvements in pain and knee function. However, the researchers reported substantial heterogeneity and rated the overall certainty of evidence as very low.
Another recent systematic review examining PBM combined with physical exercise for shoulder impingement syndrome found improvements in pain and range of motion, although improvements in overall function were not statistically significant.
These findings support a practical approach in physical therapy:
Use modalities to help create better conditions for movement, then use movement to build lasting capacity.
Is Class 4 Laser Therapy Better Than Traditional Low-Level Laser Therapy?
Not necessarily.
High-intensity laser therapy and low-level laser therapy are both forms of photobiomodulation, but they can differ substantially in power, dosage, treatment time, and other parameters.
A 2026 systematic review and network meta-analysis directly compared high-intensity and low-level laser therapy for musculoskeletal disorders. The researchers found that both approaches may provide benefits for pain and function, but differences between studies made it difficult to establish one approach as universally superior.
A 2024 umbrella review also found evidence supporting HILT for several musculoskeletal pain conditions but highlighted an important limitation: the methodological quality of existing systematic reviews varied, with some reviews receiving low or critically low quality ratings.
So, rather than asking whether Class 4 laser therapy is simply "better," the more useful question is whether the specific treatment parameters are appropriate for the patient's condition and rehabilitation goals.
What Conditions May Be Treated With Class 4 Laser Therapy?
Depending on the patient's evaluation and treatment plan, laser therapy may be considered as an adjunct for a variety of musculoskeletal conditions, including:
- Muscle pain and myofascial pain
- Tendon-related conditions
- Knee osteoarthritis
- Shoulder pain
- Patellofemoral pain
- Plantar fasciitis
- Certain sports injuries
- Joint pain
- Soft tissue irritation
- Some acute and chronic musculoskeletal pain conditions
The research does not support assuming that laser therapy will work equally well for every diagnosis. Treatment should be based on the patient's symptoms, examination findings, goals, and the current evidence for the specific condition.
What Are the Benefits of Using Laser Therapy During Physical Therapy?
For some patients, laser therapy may offer several potential benefits when incorporated into a larger rehabilitation program.
1. Pain Management
Research suggests that PBM and HILT can reduce pain in several musculoskeletal conditions, although the strength of evidence varies.
2. Supporting Movement
When pain is limiting a patient's ability to move or exercise, reducing symptoms may help create an opportunity for more productive rehabilitation.
3. Complementing Exercise
Research in conditions such as myofascial pain, plantar fasciitis, patellofemoral pain, and shoulder pain suggests that PBM can be studied alongside exercise-based rehabilitation.
4. Individualized Treatment
Laser therapy allows clinicians to adjust parameters based on the area being treated and the goals of treatment.
5. Non-Drug Pain Management
For appropriate patients, therapeutic laser is a non-pharmacological option that can be incorporated into a broader pain-management strategy.
What Are the Limitations of the Research?
The research surrounding Class 4 laser therapy is promising, but it is not definitive.
One of the biggest challenges is variation between studies.
Researchers use different:
- Wavelengths
- Power settings
- Energy doses
- Treatment frequencies
- Treatment durations
- Application techniques
- Patient populations
- Comparison treatments
This makes it difficult to compare studies directly.
Recent systematic reviews have repeatedly highlighted this heterogeneity as a limitation.
Another limitation is that evidence quality differs considerably depending on the condition being treated. Some systematic reviews report meaningful improvements in pain or function, while others find little or no clinically important benefit.
That is why a responsible physical therapy practice should avoid presenting laser therapy as a cure-all.
Is Class 4 Laser Therapy a Replacement for Exercise?
No.
For most musculoskeletal rehabilitation, exercise remains an important part of improving strength, mobility, physical capacity, and long-term function.
Laser therapy may help manage symptoms or support a patient's ability to participate in rehabilitation, but it should generally be viewed as a complementary treatment rather than a replacement for active rehabilitation.
For example, a patient experiencing knee pain may receive laser therapy as part of their treatment session, but their overall rehabilitation may also include strengthening, balance training, mobility work, gait training, and progressive loading.
The goal is not simply to make a patient feel better during the appointment.
The goal is to help the patient move better, become stronger, and return to the activities that matter to them.
The Bottom Line: What Does the Research Actually Say?
So, does Class 4 laser therapy work?
The most accurate answer is:
The research suggests that high-intensity laser therapy and photobiomodulation can reduce pain and improve function in some musculoskeletal conditions, but the effectiveness varies by condition and treatment protocol, and the quality of evidence is not equally strong across all applications.
Systematic reviews have reported positive findings for conditions including musculoskeletal pain, plantar fasciitis, knee osteoarthritis, myofascial pain, shoulder conditions, and patellofemoral pain.
At the same time, research involving nonspecific low back pain has found no clinically important benefit compared with sham treatment, demonstrating that laser therapy should not be considered universally effective for every condition.
For physical therapists, the takeaway is simple:
Laser therapy is a tool, not the entire treatment plan.
When appropriately selected and combined with evidence-based rehabilitation, it may help certain patients manage pain and participate more comfortably in the active components of physical therapy.
Class 4 Laser Therapy at Core Performance Physical Therapy
At Core Performance Physical Therapy, technology is used as part of a comprehensive approach to rehabilitation and performance.
Class 4 laser therapy may be incorporated into an individualized treatment plan based on a patient's symptoms, clinical presentation, goals, and rehabilitation needs.
The purpose is not simply to use the newest technology. It is to use the right tools at the right time to help patients move better, recover, and return to the activities they enjoy.
If you are experiencing persistent pain, recovering from an injury, or having difficulty returning to your normal activities, a physical therapy evaluation can help determine whether laser therapy or another treatment approach may be appropriate for you.
Frequently Asked Questions
How long does Class 4 laser therapy take?
Treatment time varies depending on the body region, condition, treatment parameters, and clinical goals. Your physical therapist can determine the appropriate treatment dosage and duration based on your individual evaluation.
Does Class 4 laser therapy hurt?
Therapeutic laser treatment is generally considered non-invasive. Patients may experience warmth or other sensations during treatment depending on the device and treatment settings.
How many laser therapy sessions will I need?
There is no universal number of sessions. Treatment frequency and duration depend on the condition being treated, the patient's response, and the overall rehabilitation plan.
Can laser therapy be used with exercise?
Yes. Research has specifically investigated photobiomodulation alongside exercise for several musculoskeletal conditions. In many physical therapy settings, laser therapy is used as an adjunct to active rehabilitation rather than as a replacement for exercise.
Is Class 4 laser therapy backed by scientific research?
Yes. Multiple systematic reviews and meta-analyses have investigated high-intensity laser therapy and photobiomodulation. The findings are promising for several musculoskeletal conditions, but evidence quality and treatment effectiveness vary between conditions.
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