By the RedLightPainLab Research Team · Published June 8, 2026 · Last updated June 8, 2026
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Red light therapy, also called photobiomodulation or low-level laser therapy (LLLT), can help reduce knee pain, and how well it works depends on what is causing it. The evidence is strongest for knee osteoarthritis, with support also for runner’s knee (patellofemoral pain) and patellar tendon pain. It works best alongside exercise, not on its own. Aim a near-infrared device at the knee for about 10 to 15 minutes most days.
The short version
- It helps most for osteoarthritis of the knee. Two meta-analyses found red and near-infrared light beat a placebo for knee OA pain.
- Runner’s knee responds too. A 2025 meta-analysis found a meaningful pain drop for patellofemoral pain, though the certainty is low.
- Tendon pain and post-workout soreness improve when light is added to exercise.
- Near-infrared is the part that matters, because the knee joint sits below the surface.
- It eases symptoms; it does not repair a torn meniscus or rebuild cartilage. See a clinician for a true injury.
Does red light therapy work for knee pain?
Yes for several common causes, and best for osteoarthritis. A 2019 meta-analysis in BMJ Open pooled 22 randomized placebo-controlled trials (1,063 people) and found low-level laser and light therapy cut knee osteoarthritis pain versus a sham, by about 14 mm on a 100 mm scale at the end of treatment and more during follow-up with the better-studied doses (Stausholm et al., 2019). A 2024 review in Physical Therapy (10 studies, 542 patients) agreed pain at rest dropped versus placebo (SMD -0.7, a moderate effect) but rated the certainty very low and framed it as a complement to exercise (Physical Therapy, 2024).
The honest read across all knee conditions: the effect is real but the quality of evidence is modest, and the wins are biggest when you pair the light with a real exercise plan.
How does it ease knee pain?
It works inside your cells. Red and near-infrared light is absorbed by an enzyme in the mitochondria called cytochrome c oxidase, which releases nitric oxide, restarts the cell’s energy chain, and raises ATP, the molecule that fuels repair (Hamblin, 2018). For a sore knee, that can mean less inflammation, better local blood flow, and lower pain signaling. It does not rebuild cartilage or fix a structural tear, so think symptom relief, not repair.
What knee problems does it actually help?
“Knee pain” is not one thing. Here is how the evidence stacks up by the most common causes.
| Knee problem | Best available evidence | Finding | Certainty |
|---|---|---|---|
| Osteoarthritis | Meta-analyses: 22 RCTs / 1,063 (2019) and 10 studies / 542 (2024) | Pain and disability reduced vs placebo; best with exercise | Moderate effect, low to very low certainty |
| Runner’s knee (PFPS) | Meta-analysis: 8 trials, 340 people (2025) | Pain reduced (SMD -0.83) and function improved, with exercise | Very low |
| Patellar tendon pain | Meta-analysis: 17 RCTs, 835 people (2021) | Added to exercise, improved pain and function vs sham | Very low to moderate |
| Post-exercise soreness | Meta-analysis: 14 studies (2025) | Less soreness at 72 to 96 h; faster strength recovery at 24 to 48 h | Moderate |
Sources: Stausholm 2019, Physical Therapy 2024, J Clin Med 2025 (PFPS), tendinopathy meta-analysis 2021, JFMK 2025 (recovery).
What wavelength is best for the knee, and why does depth matter?
Use a device with near-infrared light, because the knee joint sits below the surface and red light alone does not reach it well. Within the optical window of roughly 600 to 1100 nm, longer near-infrared wavelengths travel deeper. Red light near 660 nm mostly treats skin and shallow tissue, while near-infrared from about 800 to 850 nm and up reaches the deeper joint structures.
One honest caveat: most knee trials used roughly 785 to 905 nm. The case for 1064 nm reaching the deepest part of the joint is good physics, but high-quality 1064 nm knee trials are still limited, so treat deeper as a reasonable rationale, not proven fact. Our wavelength and depth breakdown goes further.
How to use red light therapy on your knee at home
The protocols that worked in studies were simple: aim the light right at the knee, keep sessions short, and repeat them for several weeks. One knee osteoarthritis study even treated both sides of the knee for 15 minutes twice a day. A practical starting routine:
- Pick a device with near-infrared (around 800 to 850 nm or longer), not a red-only panel.
- Sit 6 to 24 inches from the knee, with bare skin facing the light.
- Run 10 to 15 minutes per session, about 4 to 5 days a week.
- Treat the knee from a few angles: the front, the sides, and behind the joint.
- Keep up your strengthening and mobility work; the combination is what the trials rewarded.
- Give it 4 to 8 weeks, then reassess. Wear the eye protection.
Is it safe for your knee? Who should skip it?
The safety record is strong. Knee trials reported few or no adverse events. The occasional issue is minor: eye strain without goggles, mild warmth, or brief redness from sitting too close. Wear the eye protection that ships with the device, follow the recommended distance and time, and check with your doctor first if you are pregnant, take a medication that makes you sensitive to light, have a condition that does, or have a knee injury that has not been properly diagnosed.
How does it compare with other knee pain options?
Treat it as one tool, not a replacement. For most knee pain the backbone is still movement: strengthening, mobility, weight management, and physical therapy, with NSAIDs or, in some cases, injections for flares. Red light therapy is drug-free and low risk, which makes it a reasonable add-on, especially if you want to lean on pain pills less. If your pain comes from a torn meniscus, ligament damage, or advanced joint disease, see a clinician; light therapy manages symptoms, it does not fix structural damage.
What does it cost?
Expect to pay out of pocket. Insurance in the US rarely covers red light therapy for knee pain, since it is treated as a general wellness tool. You are choosing between paying a clinic per visit across a multi-week course, or buying a home device once and using it as often as you like. Home units tend to be less powerful than clinic machines, so they can take longer to work, which is the trade-off for the lower running cost.
Choosing a device for knee pain
For a knee, look for real near-infrared output at enough power to reach the joint from a comfortable distance, with third-party-tested specs rather than marketing numbers. A wrap or pad style can make it easier to cover the knee from several angles. We rank options on exactly these factors in our top 5 devices for pain. As an independent site, our current top pick for depth and value is the RLT Home TotalSpectrum, which carries near-infrared and deep near-infrared bands suited to joints.
Frequently asked questions
Does red light therapy really work for knee pain?
For several common causes, yes, and best for osteoarthritis. Meta-analyses show red and near-infrared light reduce knee OA pain versus placebo, with support also for runner’s knee and tendon pain. The effect is real but the evidence quality is modest, so use it alongside exercise.
How long until red light therapy helps my knee?
Give it a few weeks. Benefits build over a course of sessions and often keep improving for a couple of weeks afterward. A fair trial is 10 to 15 minutes per session, 4 to 5 days a week, for 4 to 8 weeks, then reassess.
What wavelength is best for the knee?
Near-infrared, because the joint is deep. Most successful knee trials used roughly 785 to 905 nm. A 660 nm red-only panel is built for skin, so for the knee choose a device with near-infrared, and ideally deep near-infrared for the deepest structures.
Can red light therapy heal a meniscus tear or cartilage?
No. The evidence is for reducing pain and improving function, not for repairing a torn meniscus or rebuilding cartilage. For a suspected structural injury, get it diagnosed; use light therapy only as symptom support around proper care.
How often should I use it on my knee?
About 4 to 5 days a week, 10 to 15 minutes per session, treating the knee from a few angles. Some study protocols used twice-daily sessions for short courses. More is not automatically better; consistency over several weeks matters most.
Is red light therapy FDA approved for knee pain?
Red light therapy panels are FDA registered, not FDA cleared or approved. Registration means the device is listed with the FDA as a general wellness product; it is paperwork, not proof it treats knee pain. Some medical laser units carry 510(k) clearance, but consumer panels do not.
References
- Stausholm MB, et al. Efficacy of low-level laser therapy on pain and disability in knee osteoarthritis. BMJ Open. 2019;9(10):e031142. PubMed
- Effectiveness of photobiomodulation in reducing pain and disability in patients with knee osteoarthritis. Physical Therapy. 2024;104(8):pzae073. Journal
- Photobiomodulation therapy on pain and function in patellofemoral pain syndrome. Journal of Clinical Medicine. 2025;15(1):20. PMC
- Low-level red and near-infrared photobiomodulation on pain and function in tendinopathy. 2021. PMC
- Photomodulation therapy for delayed onset muscle soreness. J Funct Morphol Kinesiol. 2025;10(3):277. MDPI
- Hamblin MR. Mechanisms and mitochondrial redox signaling in photobiomodulation. Photochemistry and Photobiology. 2018;94(2):199-212. PMC
Medical disclaimer: This article is for informational purposes only and is not medical advice. Always consult a qualified healthcare professional before starting any new treatment, including red light therapy.
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