Class IV laser therapy — also written class 4 laser therapy, and known clinically as photobiomodulation — uses concentrated therapeutic light to stimulate healing and reduce pain at a cellular level. You'll also see it called high-intensity laser therapy, level 4 laser, or simply IV laser.
The naming is inconsistent across clinics, which adds to the confusion. Class 4 laser, class four laser therapy, class 4 therapeutic laser, class IV laser treatment and level 4 laser all refer to the same thing — therapeutic lasers rated above 500 milliwatts. Some clinics simply say class 4 lasers or IV laser.
It's one of the more misunderstood treatments in musculoskeletal care, partly because of how it's marketed. Here's a straight explanation of what it actually does, what it treats, and where the evidence is genuinely strong versus thin.
What is Class IV laser therapy?
Therapeutic laser delivers specific wavelengths of light into tissue. Crucially, this is not a surgical laser — surgical lasers cut and ablate tissue, while therapeutic lasers use wavelengths and intensities chosen to produce biological effects without damaging anything.
The light is absorbed by structures inside your cells, principally cytochrome c oxidase in the mitochondria. That absorption sets off a cascade:
- Increased cellular energy production (ATP)
- Reduction in inflammatory mediators
- Improved local circulation and lymphatic drainage
- Stimulated fibroblast activity, supporting tissue repair and collagen remodelling
- Modulated pain signalling along peripheral nerves
What "Class IV" actually means — the part most sites get wrong
This matters, so we'll be blunt about it.
The class number is a laser safety classification based on risk of eye injury. It is not a rating of therapeutic power or clinical effectiveness. Class IV means the device outputs more than 500 milliwatts, which is why protective eyewear is mandatory. Class 3B covers devices at 500 milliwatts and below.
| Class 3B (LLLT) | Class IV / class 4 | |
|---|---|---|
| Power output | Up to 500 mW | Above 500 mW — commonly 0.5–15 W |
| Penetration depth | More superficial | Deeper, roughly 4–5 cm |
| Session length | Longer for the same dose | Shorter, typically 5–15 min |
| Best suited to | Superficial tissue | Deeper structures — hip joints, thick tendons, deep muscle |
Higher power does bring real practical advantages: more energy delivered to deeper structures, and shorter appointments. But a higher class number doesn't automatically mean better outcomes. What actually matters is the dose delivered to the target tissue — and it's worth knowing that a lot of Class IV marketing cites research that was performed using Class 3B devices.
What conditions does class 4 laser therapy treat?
Tendon and soft tissue conditions
- Tennis elbow and golfer's elbow
- Rotator cuff tendinopathy and shoulder pain
- Plantar fasciitis and heel pain
- Achilles tendinopathy
- IT band syndrome
- Muscle strains and ligament sprains
Joint and arthritic conditions
- Osteoarthritis — knee, hip, hand and shoulder
- Frozen shoulder
- TMJ dysfunction
- Carpal tunnel syndrome
Spinal and chronic pain
- Back pain and neck pain
- Sciatica and radiating pain
- Myofascial pain and trigger points
Recovery
- Post-surgical tissue healing and rehabilitation
- Recovery between training sessions for athletes
- Post-collision soft tissue healing
Where the evidence is strong — and where it isn't
We'd rather give you an accurate picture than a promotional one.
Reasonably supported: chronic tendinopathies, osteoarthritis pain, and superficial soft tissue conditions have the most consistent evidence behind them. The FDA first cleared a Class IV therapeutic laser in 2003 for musculoskeletal pain, inflammation and tissue healing.
Less convincing: results for acute, deep-tissue injuries are mixed, and many studies show no clear functional advantage over conventional treatment. A genuine limitation across this whole research area is that wavelength, power, dose and treatment frequency vary enormously between studies, which makes them hard to compare and pool.
The practical conclusion: laser is a useful adjunct with an excellent safety profile — not a cure, and not a substitute for addressing why the tissue got overloaded in the first place.
What a laser therapy session is like
Sessions are short — typically 5 to 15 minutes depending on the size of the area. The clinician moves the handpiece slowly over the region in a set pattern, and you'll feel a gentle spreading warmth. There's no pain, no needle, and no downtime afterwards.
Everyone in the room wears protective eyewear. At this power level that's a requirement, not a formality — and it's the main practical reason the Class IV designation exists.
How many sessions will you need?
- Acute injuries: around 4–8 sessions over 2–3 weeks
- Chronic conditions: 8–12 or more over 4–6 weeks
- Athletic recovery: weekly or as needed
The effect is cumulative, so a course is normal and many people notice a change within the first two or three sessions. If you've had several with no change at all, that's a reason to reassess the diagnosis rather than keep booking.
Is laser therapy safe?
Yes, when applied by a trained clinician. It's avoided or modified in these situations:
- Directly over the eyes — protective eyewear is worn throughout
- Over the abdomen during pregnancy
- Directly over known active malignancy
- Over areas of active bleeding
- With photosensitizing medications — tell your clinician what you take
- Caution over pacemakers and certain implants
Side effects are rare. Some people report mild soreness after a first session, which settles quickly.
Laser or shockwave?
Both are useful and they overlap. Shockwave uses mechanical energy, tends to suit chronic degenerative and calcific tendon problems, and is often uncomfortable during treatment. Laser uses light energy, is painless, and suits pain-dominant and inflammatory presentations. Which one depends on your diagnosis and tolerance — frequently we use both across a plan.
Class IV laser at THE WAY Chiro
We use Class IV laser as part of an integrated plan rather than a standalone service — alongside chiropractic treatment, soft tissue therapy and rehabilitation, because the laser reduces pain and supports healing while the underlying mechanical problem gets addressed.
Full details on the treatment, including pricing and coverage: Class IV laser therapy in Oakville.
We serve patients from Oakville, Mississauga and Burlington, with evening and Saturday appointments.
Frequently asked questions
What is class 4 laser therapy?
Class 4 laser therapy, also called Class IV laser or photobiomodulation, uses high-power therapeutic light above 500 milliwatts to stimulate cellular repair and reduce pain. It is a treatment laser, not a surgical one — it does not cut or burn tissue.
What does the class 4 designation mean?
It is a laser safety classification based on risk of eye injury, not a measure of therapeutic strength. Class 4 means output above 500 milliwatts, which requires protective eyewear during treatment. Class 3B devices operate at 500 milliwatts and below.
Is class 4 laser better than class 3B?
Not automatically. Higher power allows deeper penetration and shorter sessions, which are real advantages. But the class number rates eye-safety risk rather than clinical outcome, and much of the published photobiomodulation research used Class 3B devices. The dose delivered to the tissue matters more than the class.
Does class 4 laser therapy hurt?
No. Most people feel a gentle, spreading warmth as the handpiece moves over the area, and some feel nothing at all. There is no pain and no downtime.
How many laser therapy sessions do I need?
Acute injuries typically need four to eight sessions over two to three weeks. Chronic conditions often need eight to twelve or more over four to six weeks. The effect is cumulative, and many people notice a change within the first two or three sessions.
Are there side effects from laser therapy?
Side effects are rare. Some people report mild soreness after a first session, which typically resolves quickly. Protective eyewear is worn to prevent eye exposure.
What conditions does class 4 laser treat?
It is most commonly used for tendinopathies such as tennis elbow, Achilles and rotator cuff problems, plantar fasciitis, osteoarthritis pain, chronic neck and back pain, myofascial pain, and post-surgical or post-injury tissue healing.
Is laser therapy covered by OHIP?
No. Laser therapy is not covered by OHIP. When delivered within a chiropractic appointment, the visit may be claimable under your extended health plan's chiropractic coverage.