Red Light Therapy for Knee and Hip Pain: Does It Work?

This comes up in the office regularly. A patient has bought a red light panel, or a wrap that goes around the knee, or has seen one advertised, and wants to know whether it is worth it.

I will give you the same answer I give them, which is less satisfying than either of the answers available online.

The short answer

I do not have a strong recommendation either way. Some of my patients get real relief from it. Some use it faithfully and get nothing. The literature is not strong enough to say it works — which is not the same as saying it does not.

There is very little harm in trying it. If you are interested, I would not talk you out of it. The thing I would most like to protect you from is the price.

What red light therapy is

The formal term is photobiomodulation, and in clinical research you will also see it called low-level laser therapy.

The idea is that light at particular wavelengths is absorbed inside cells — specifically by cytochrome c oxidase, an enzyme in the mitochondria — and that this influences cellular energy production and inflammatory signaling. There is real laboratory work behind that mechanism.

Worth being clear about the step that follows: a plausible mechanism with laboratory support is not the same as demonstrated benefit in patients. Plenty of treatments have cleared the first bar and failed the second. This one sits in between, which is precisely why the answer is unsatisfying.

What the research shows

There is a genuine body of research here — this is not an area with nothing behind it, and it is worth distinguishing from treatments where the human evidence is essentially absent.

Some randomized trials have reported meaningful pain reduction in knee osteoarthritis, and pooled analyses have found improvements in pain at rest and in disability scores. Reviews describe some of that evidence as moderate in certainty, and several conclude it is reasonable as an addition to an exercise program.

Other trials have found little or no benefit. Reviewers describe the overall picture as varied and, in their own words, controversial. And the practical marker worth knowing: it is not recommended in the major treatment guidelines for knee osteoarthritis. Guideline panels look at the same literature and have not found it strong or consistent enough to endorse.

That is the accurate summary. Not nothing, not established.

Why the studies disagree

This part is genuinely interesting, and it explains a lot.

The trials did not test the same thing. They used different wavelengths, different power outputs, different session lengths, different numbers of sessions, and different distances from the skin. In drug terms, they were testing different doses of different compounds and reporting them all under one name.

The studies showing benefit have generally used devices with verified output delivering doses in a fairly specific range. Some of the negative studies may have been underdosing — delivering light that never reached the tissue in question in a meaningful amount.

That does not prove it works. What it does mean is that red light therapy does not work is too broad a conclusion to draw from a literature this heterogeneous, and so is the opposite.

Red light versus near-infrared

If you take one practical thing from this page, take this one.

Visible red light penetrates only a few millimeters into tissue. That is relevant for skin, and it is why red light has a much better established role in dermatology. It does not reach the inside of a knee.

Near-infrared penetrates considerably deeper — wavelengths generally in the 800 to 850 nanometer range are what the joint-focused research uses, because those can plausibly reach the capsule and deeper structures.

Most devices sold for joint pain combine both, and the red is the part you can see. If you are buying something for a knee or a hip, the near-infrared component is the part that matters, and a device that is only visible red is unlikely to be doing much at depth regardless of how impressive it looks.

One related point: tissue thickness over the joint affects how much light arrives. A knee with more soft tissue over it is a harder target, which is another source of variability between people.

Clinic devices and home devices

The research was largely conducted with clinical devices with calibrated and verified output. Consumer panels and wraps are a different category, and manufacturer specifications are not always independently verified.

That is not an accusation against home devices. It is a reason the results people get at home vary more than the trial results do, and a reason to be skeptical of a device whose claims are impressive but whose actual output at treatment distance is not stated clearly.

What these cost

This is where I have the strongest opinion on the whole subject, and it is about money rather than biology.

These products range from modest to genuinely expensive, and price does not reliably track with effectiveness. Large full-body panels are priced around a cosmetic and wellness market — skin, sleep, general use. Treating one arthritic knee is a much narrower goal, and a smaller targeted device aimed at that joint may do the same job for a fraction of the cost.

My advice, if you want to try this: start at the cheaper end. You are running an experiment on yourself with an uncertain outcome, and there is no reason to spend heavily on the first attempt. If a modest device helps, you have your answer. If it does nothing over a couple of months, an expensive one is not an obvious next step.

Why I do not discourage it

Serious adverse effects are rarely reported. It is non-invasive, drug-free, does not interact with medication, and does not rule out anything else you might do for the joint.

That low risk is a substantial part of why my answer is go ahead if you want to rather than do not bother. When something is unproven but nearly harmless, and a patient is interested, the calculation is different from something unproven and risky.

Sensible precautions: do not look directly into the light, follow the manufacturer’s guidance on session length rather than assuming more is better, and take advice first if you have a condition that causes light sensitivity or take a medication that does.

If you want to try it

A few things that make the experiment worth running properly:

• Choose a device with near-infrared, not visible red alone, if the target is a joint.
• Use it close to the skin and directly over the joint. Distance reduces the dose quickly.
• Be consistent for a defined period — several sessions a week for six to eight weeks — rather than using it occasionally and concluding nothing happened.
• Decide in advance what improvement would look like, then judge it honestly at the end. Arthritis symptoms fluctuate on their own, which makes casual assessment unreliable.
• Keep doing the things that are established — this is an addition, not a replacement.

What it will not do

Nothing here changes the structure of an arthritic joint. Cartilage that is gone does not return, and the positive studies measured pain and function rather than repair.

If a device is marketed as regenerating cartilage or reversing arthritis, that claim is well past the evidence. I go through what actually can and cannot restore a joint surface in can arthritis be reversed.

Where it fits

Red light therapy belongs in the same category as several things patients ask me about — plausible, low-risk, inconsistently supported, and reasonable to try if you are curious and not overspending.

What I would not want is for it to substitute for the things that reliably work. Strength, weight, and activity choices do more for an arthritic hip or knee than anything in this category, and they are covered in physical therapy for arthritis, activity modification and non-surgical treatment for hip and knee arthritis. The other things patients ask about most are in supplements I discuss with orthopedic patients.

And the question underneath all of it is usually what is actually wrong with the joint. If a knee or hip has been bothering you long enough that you are buying devices for it, an examination and a weight-bearing X-ray tell you what you are dealing with — whether it is knee osteoarthritis, hip osteoarthritis, or something else entirely. That answer shapes everything, including whether an experiment like this one is worth your time.