Sore tendons are one of the top reasons people buy a red light device. Tennis elbow, Achilles pain, and heel pain all feel similar. They ache, they stiffen, and they take a long time to settle. So it is fair to ask a simple question. Does red light therapy actually help a bad tendon heal?

The honest answer is interesting. The same light gets different grades depending on which tendon you point it at. Let us walk through what the studies really show, in plain terms, so you can spend your time and money well.

A quick word on terms

A tendon is the tough cord that ties a muscle to a bone. When a tendon gets overused, it can become sore, thick, and weak. Doctors call this tendinopathy. It is not a clean tear. It is more like a slow breakdown from too much load and not enough recovery.

Red light therapy is also called photobiomodulation, or PBM for short. When a laser is used, it is called low-level laser therapy, or LLLT. All three names describe the same basic idea. You shine red or near-infrared light on the tissue to change how the cells behave.

Here is the leading theory for how it may help. The light is soaked up by mitochondria, the tiny power plants inside your cells. This can give cells more energy. It can also calm the chemical signals that drive swelling. And it may support the repair cells that rebuild collagen, the main building block of a tendon. That is a promising recipe. But a good theory is not the same as a good result. So let us look at the tendons one by one.

Tennis elbow: the evidence looks good

Tennis elbow is pain on the outside of the elbow. You do not need to play tennis to get it. Any gripping or lifting can bring it on.

A large review pulled together the trials on light therapy for tennis elbow. It looked at 18 randomized studies. Thirteen of them, covering about 730 people, were strong enough to pool together. The result was positive. When the light was aimed right on the sore tendon, people had less pain and a stronger grip. The benefit held up for weeks after the sessions ended. No serious side effects showed up.

One detail matters a lot. The benefit was dose-dependent. That means the amount of light energy had to be in the right range to work. The doses in the helpful trials sat between about half a joule and seven joules per spot. A joule is just a unit of light energy. Too little light, and there was no real effect. So for tennis elbow, red light looks like a fair helper, as long as it is used well.

The Achilles tendon: light adds little on top of exercise

Now the picture changes. The Achilles is the big tendon at the back of your ankle. It takes a huge load every step you run.

A 2024 trial from New Delhi tested this well. It included 60 people with Achilles pain. Everyone did the same proven exercise. It is a slow heel-drop move that loads the tendon on purpose, done twice a day for 12 weeks. This kind of loading is called eccentric exercise. One group also got a real laser. The other group got a fake laser that looked the same. The exercise was the real treatment.

Both groups got much better. Their function scores climbed from about 47 to about 85 out of 100. Their pain dropped by two-thirds. But here is the key point. The two groups ended up in the same place. Adding the laser did not beat the exercise alone.

This was not a one-off. A 2012 trial and a 2020 review of four studies found the same thing. For the Achilles tendon, light does not seem to add much once you are already doing the loading work.

Heel pain: helpful, but not the only option

Plantar fasciitis is a common cause of heel pain. The plantar fascia is a thick band of tissue along the bottom of your foot. It acts a lot like a tendon.

A 2019 review of six trials found that light therapy did lower heel pain. The relief was real and lasted about three months. One summary put the drop at roughly 40 percent on a pain scale. So this is a point in favor of red light.

There is a fair catch, though. When researchers compared light to shockwave therapy, a different treatment that uses sound waves, the shockwave did as well or better. So light is one good tool for heel pain. It is not the only one, and it may not be the strongest.

What this means for you

Put these three tendons together and a clear message appears. Red light therapy is not a magic switch for tendons. It is a helper whose value depends on three things.

First, it depends on the tendon. A study on tennis elbow does not prove anything about your heel or your Achilles. Match the evidence to your body part.

Second, it depends on the loading work. For any sore tendon, slow and steady loading exercise is the best-proven treatment. Light may lower your pain enough to let you do that work. It does not replace the work.

Third, it depends on aim and dose. The benefits showed up when the light hit the exact sore spot at the right energy. A weak mask waved near the area is not the same as a focused device pressed on the tendon. Many at-home panels are lower power than clinic lasers, so results can be slower or weaker.

The bottom line

Red light therapy has a real, if modest, place in tendon care. It looks most useful for tennis elbow and heel pain, and less useful for the Achilles once you are already doing your exercises. Used as a helper next to good loading work, it is safe and may take the edge off your pain. Used as a shortcut instead of the exercises, it is likely to disappoint.

If your pain is severe, came on suddenly, or feels like a tear, see a clinician first. A tendon that is torn needs a different plan than one that is simply overused.

The science here is still growing. Better devices and clearer dosing rules may lift these results in the years ahead. For now, treat red light as a smart sidekick for your tendons, not the star of the show.

References

• Bjordal JM et al. Low level laser therapy in lateral elbow tendinopathy (tennis elbow): systematic review and meta-analysis. BMC Musculoskeletal Disorders. 2008. Link
• Shriya S et al. Low-Level Laser Therapy Combined With Eccentric Exercise in Midportion Achilles Tendinopathy: A Randomized Controlled Trial. Cureus. 2024. Link
• Martimbianco AL et al. Photobiomodulation with low-level laser therapy for treating Achilles tendinopathy: a systematic review and meta-analysis. Clinical Rehabilitation. 2020. Link
• Clinical efficacy of low-level laser therapy in plantar fasciitis: a systematic review and meta-analysis. Medicine (Baltimore). 2019. Link