March 31, 2026 Jacky Chan

Knee Pain and Red Light Therapy: What the Research Says

This article is for general education and isn't medical advice. Talk to your doctor or physical therapist before starting any new therapy, especially if you have a diagnosed condition, are pregnant, or take medications that increase light sensitivity.

Knee pain is one of the most common complaints I hear as a trainer. It shows up in runners, in lifters, in people who are on their feet all day, and in people living with arthritis. Red light therapy comes up a lot in that conversation, and knee osteoarthritis is one of the more researched areas for this technology. Here's a plain-language look at what the research says, where it's still uncertain, and how light therapy fits into a bigger picture that starts with a proper diagnosis.

Why Knees Hurt: Common Causes

Knee pain can come from an injury, from overuse, or from a medical condition. Mayo Clinic lists common causes including:

Injuries such as a torn ACL or meniscus, fractures, bursitis and patellar tendinitis
Osteoarthritis, a wear-and-tear condition in which the cartilage in the knee breaks down with use and age
Other types of arthritis, including rheumatoid arthritis, gout and joint infection
Patellofemoral pain, a general term for pain between the kneecap and the thighbone, common in athletes and young adults

Because these causes are so different, the right next step depends on what's actually going on. Mayo Clinic advises contacting your doctor if you can't bear weight on the knee, it feels unstable or gives way, you have marked swelling, you can't fully straighten or bend it, there's an obvious deformity, or you have a fever along with redness, pain and swelling around the knee.

What Red Light Therapy Is

Red light therapy, also called photobiomodulation (PBM), uses low levels of red and near-infrared light. Many studies use the older name, low-level laser therapy (LLLT), because they used lasers rather than LEDs. Cleveland Clinic explains that it's thought to work by acting on mitochondria, the energy-producing parts of cells. It lists knee osteoarthritis among the uses researchers are investigating, while also noting there isn't enough evidence yet to support most uses.

A widely cited 2017 review in AIMS Biophysics identifies cytochrome c oxidase, an enzyme in mitochondria, as the main molecule that absorbs this light. It also explains that the effects depend on dose, with low doses and high doses behaving differently, so more light is not automatically better. For more background, see our red light therapy 101 guide.

What the Research Shows for Knee Osteoarthritis

Knee osteoarthritis is where most of the clinical research on light therapy and joints has focused. Some of it is encouraging, some of it isn't, and the details matter.

A meta-analysis of placebo-controlled trials

A 2019 systematic review and meta-analysis in BMJ Open pooled 22 randomized, placebo-controlled trials involving 1,063 people with knee osteoarthritis. The authors reported that low-level laser therapy reduced pain and disability compared with placebo, that the effects were larger at the doses they considered recommended, and that no adverse events were reported. Keep in mind that these trials used laser devices at specific wavelengths and doses, so the results don't automatically carry over to any particular home device.

A large trial that found no benefit

Not every study agrees. A 2014 randomized trial in JAMA followed 282 people over 50 with moderate to severe chronic knee pain. Neither laser acupuncture nor needle acupuncture did better than a sham (inactive) laser for pain or function, and the authors concluded their findings did not support acupuncture for these patients. Laser acupuncture isn't the same thing as a red light panel or wrap, but this trial is a useful reminder that results depend heavily on how a study is designed and what the treatment is compared against.

Runner's knee (patellofemoral pain)

A systematic review and meta-analysis published in late 2025 in the Journal of Clinical Medicine looked at eight small randomized trials (340 participants) of photobiomodulation for patellofemoral pain syndrome. Pooled results favored PBM, mainly when it was combined with exercise, but the certainty of the evidence was rated very low and the authors called for larger, higher-quality trials and standardized dosing.

The bottom line on the evidence

Red and near-infrared light is one of the more studied non-drug options for knee osteoarthritis, and some pooled analyses report benefits compared with placebo. At the same time, results are mixed, many trials are small, and devices and doses vary widely. The fair description is an active area of research with mixed results, not a proven treatment.

Movement Still Matters

As a trainer, this is the part I care about most. Exercise has been studied much more extensively for knee osteoarthritis. Cochrane's 2024 review of exercise for knee osteoarthritis, which drew on dozens of trials, found that exercise may improve pain and physical function compared with no treatment, usual care or limited education. The authors were also candid that the size of the benefit is of uncertain clinical importance and that many of the studies were small.

In general training terms, a sensible knee-friendly program usually includes:

Strength work for the muscles around the knee and hip, such as the quadriceps, hamstrings and glutes
Range-of-motion and mobility work that the knee tolerates
Gradual increases in load, adjusted based on how the knee feels over the next day or two

The specifics, especially after an injury or surgery or with diagnosed arthritis, should come from your doctor or physical therapist.

If You're Thinking About Trying It at Home

Talk to your doctor or physical therapist first, especially if you have a diagnosed condition or recent surgery.
Follow the manufacturer's instructions for session length, distance and frequency. There is no established home dose for any knee condition.
Protect your eyes. Cleveland Clinic advises shielding your eyes when using at-home devices.
Check with your doctor if you're pregnant, have a light-sensitive skin condition, or take medications that increase light sensitivity.
Watch for warning signs. A knee that gives way, won't bear weight, or is hot, red and swollen with a fever needs medical attention, not another session.
Keep expectations realistic. Cleveland Clinic says red light therapy appears safe when used short-term and as directed, but the long-term safety of these devices isn't yet known.

If you're curious what at-home devices look like, you can browse our red light therapy collection. We're happy to answer questions about a device's specs, but decisions about your knee belong with your doctor or physical therapist.

Sources

Written by Jacky Chan, certified personal trainer, stretch therapist and massage therapist, and founder of Peak Flow Fitness. Have a question about the equipment in this guide? Contact our team.

Filed in: joint pain, knee pain, osteoarthritis, photobiomodulation, recovery, red light therapy

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