Does Red Light Therapy Help Knee Arthritis Pain?

Yes, modestly. Across 22 placebo-controlled trials, light therapy on the knee lowered osteoarthritis pain by about 14 points on a 100-point scale more than a fake device. The trials that worked mostly used invisible near-infrared lasers at a set dose, and in people already doing a strengthening program, adding light made no difference.

“Red light therapy” is the everyday name for what researchers call photobiomodulation, or low-level laser therapy. It shines red or near-infrared light on the skin over a sore joint. Osteoarthritis is wear-related damage to the cartilage that cushions the joint, and the knee is one of the joints it affects most often.

What the Data Show

The largest analysis pooled 22 randomized placebo-controlled trials with 1,063 people. A placebo device looks and sounds the same but gives no light, so the comparison separates the light from the ritual of treatment. Pain dropped about 14 points (on a 0 to 100 scale) more with real light than with the placebo at the end of treatment. When the dose matched expert recommendations, the gap grew to about 19 points, and it peaked at about 32 points 2 to 4 weeks after treatment ended. Disability also improved, and no side effects were reported.

A 2024 meta-analysis of 10 placebo-controlled trials with 542 people, the paper this page was first written about, found the same direction. Light therapy reduced pain at rest, a moderate effect. But all 10 trials had unclear to high risk of bias, the authors rated the certainty very low, and a timed walking test did not improve. They concluded it should not be used alone but may be added to other recommended treatments.

Not every review agrees. A 2015 meta-analysis of 9 trials with 518 patients found no significant difference in pain between real and sham laser, even in trials that followed the recommended dose. It concluded the evidence did not support laser for knee osteoarthritis. More trials have been published since then, and the newer reviews lean positive.

An umbrella review that graded 15 meta-analyses rated the evidence that light therapy reduces knee osteoarthritis disability as moderate certainty, one of its better-supported uses.

Which Red Light Therapy Is Best for Knees: Red or Infrared?

This matters more than the brand. Most of the trials that worked did not use visible red light. They used near-infrared lasers, which you cannot see.

The 22-trial analysis found pain relief at 4 to 8 joules per treatment spot with 785 to 860 nm light, and at 1 to 3 joules per spot with 904 nm light. A joule is a measure of the light energy delivered. Visible red light runs from about 600 to 700 nm.

A network meta-analysis of 13 trials with 673 people ranked wavelengths against each other. Light therapy beat sham for pain but not for function or stiffness. The 904 to 905 nm wavelength ranked best for pain, and 785 to 850 nm also beat sham. Devices mixing several wavelengths did not reliably beat sham.

Only one knee trial compared red and infrared directly. In that randomized trial of 47 people, 808 nm infrared improved thigh muscle strength more than 660 nm red light and more than sham. The red light group did better on a sit-to-stand test. That trial measured strength and function, not pain.

Light type	What the knee trials found
904 to 905 nm infrared laser	Ranked best for pain relief
785 to 860 nm infrared laser	Beat sham for pain at 4 to 8 joules per spot
Multi-wavelength devices	Not reliably better than sham
660 nm visible red	Less strength gain than 808 nm in one trial; little pain data

Does Red Light Therapy Help If You Already Exercise?

Probably not much. Exercise is the best-tested treatment for knee osteoarthritis, so this is the question that matters most.

In a six-month trial of 127 people, everyone did strengthening exercises three times a week for 8 weeks. One group also got real light therapy, one got a placebo device, and one got exercise alone. All three groups had meaningful drops in pain and better function, and there was no difference between them at any point.

A 52-week trial of 50 people paired strength training with real or placebo laser. Pain fell substantially in both groups, with no difference in the main pain measures. At one year, fewer people in the laser group were using pain pills, and they did better on a sit-to-stand test.

A smaller trial of 40 people aged 50 to 75 gave 10 laser sessions before an 8-week exercise program. Pain and function scores were the same in both groups at 3 and 6 months, but the laser group used less acetaminophen (paracetamol) throughout follow-up.

So light therapy does not appear to add pain relief on top of a good exercise program, though two trials hint that it may reduce the need for pain pills.

How Many Sessions Does Red Light Therapy Take for Knees?

The trials gave 2 to 3 sessions a week for 3 to 8 weeks. Examples: 10 sessions over 3 weeks, or 15-minute sessions three times a week for 8 weeks. No trial compared different session counts head to head.

The relief outlasted the sessions. In the 22-trial analysis, the benefit at recommended doses peaked 2 to 4 weeks after treatment stopped and was still measurable up to 12 weeks later. No trial has tested ongoing use for years.

How Does Red Light Therapy Work on Joints?

The leading explanation starts in the mitochondria, the energy factories inside cells. A review of the mechanism describes an enzyme there that absorbs red and near-infrared light. That raises the cell’s energy supply (ATP) and nitric oxide, and one of the most consistent downstream effects is less inflammation, which matters for joints.

The same review describes a biphasic dose response: a little light stimulates cells, while too much can have the opposite effect. That is one reason “more is better” does not apply, and why doses in the trials were specific. These mechanisms come mostly from lab and animal work. The knee trials measured pain and function, not what happened inside the joint.

Does Red Light Therapy Work for Other Arthritis?

The evidence is best for the knee. For other joints it is weaker.

Hand osteoarthritis: in a randomized trial of 88 people, laser three times a week for 6 weeks was no better than placebo for pain, morning stiffness or function.

Rheumatoid arthritis: a meta-analysis of 18 trials with 793 people found low-quality evidence that infrared laser may be no better than sham for pain, stiffness, grip strength or inflammation. The evidence on red laser was too uncertain to call.

Is Red Light Therapy Safe for Knees?

Across the 22 placebo-controlled knee trials, no adverse events were reported. Low-level light does not heat or cut tissue. The general precautions are to protect your eyes from laser light and to get any new or unusual knee symptoms checked rather than treating them yourself.

Dr. Kumar’s Take

Light therapy for knee arthritis is better supported than most people assume, and weaker than device ads suggest. The placebo-controlled trials show a real drop in pain, about 14 points on a 100-point scale on average. That is noticeable, but it is not a cure, and the reviews disagree on how solid it is.

The catch is in the details. The trials that worked used near-infrared lasers at a measured dose per spot, which is not what most home red light panels deliver. And when people were already doing strength training, the light added little. If I had to rank the options, the exercise comes first and the light is an add-on for the person who is still hurting.

Practical Takeaways

Start with strengthening exercise. In the trials, it improved pain and function on its own, with or without light.
Expect modest relief, not a cure. The average gain was about 14 points on a 100-point pain scale.
Look at the wavelength. The positive trials used near-infrared, mostly 785 to 860 nm or 904 to 905 nm, not visible red alone.
Dose matters. The trials delivered a set number of joules per spot, 2 to 3 times a week, for 3 to 8 weeks.
Do not expect help for hand or rheumatoid arthritis. Trials there found no clear benefit over placebo.
See a doctor for a knee that is hot, red, badly swollen, locking or giving way.

FAQs

Does red light therapy really work for knee pain?

For knee osteoarthritis, placebo-controlled trials show a modest drop in pain, about 14 points on a 100-point scale on average. Reviews disagree on how certain that is, and one 2015 analysis found no clear benefit. It is an add-on, not a replacement for exercise.

Is red or infrared light better for knee arthritis?

Most trials that reduced knee pain used near-infrared light, around 785 to 860 nm or 904 to 905 nm. In the one direct comparison, 808 nm infrared improved thigh strength more than 660 nm red. Infrared also reaches deeper than visible red.

How long does it take red light therapy to work on knees?

Trials ran 2 to 3 sessions a week for 3 to 8 weeks. The pain relief peaked 2 to 4 weeks after the sessions ended and was still present up to 12 weeks later.

Can red light therapy repair knee cartilage?

No human trial in this review showed cartilage regrowth. The knee trials measured pain and function, and the anti-inflammatory effects come mainly from lab and animal studies.

Does red light therapy help arthritis in other joints?

The evidence is weaker outside the knee. A hand osteoarthritis trial found laser no better than placebo, and a rheumatoid arthritis meta-analysis found infrared laser may be no better than sham.

Bottom Line

Red light therapy, mostly in the form of near-infrared laser, modestly reduces knee osteoarthritis pain compared with a placebo device, and the relief lasts a few weeks after treatment. The evidence is mixed in quality, and it did not add benefit for people already doing strengthening exercise. Exercise first, then light as an add-on if the knee still hurts.

Does Red Light Therapy Help Knee Arthritis Pain?