Pain in the back of the ankle, stiffness in the morning, and an Achilles tendon that feels thick and tender to the touch. Many are familiar with the symptoms, and they can be frustrating because tendon tissue typically responds slowly to treatment.
Laser and light therapy, also called photobiomodulation (PBM), is often mentioned as an option when you want to reduce pain and support healing. But how do you best give it a fair chance, without overtreating or overlooking the most important building blocks in rehabilitation?
What is meant by Achilles tendinitis?
The term “Achilles tendinitis” is commonly used for pain in the Achilles tendon, but in many cases it is more accurate to call it Achilles tendinopathy. It covers both irritation close to the heel bone (insertional) and pain higher up on the tendon (mid-portion).
Tendon problems often arise when the load increases faster than the tissue can adapt. This can be more runs, more hill or interval running, new shoes, more sports during the holidays, or a period of less movement followed by a quick comeback.
A typical pattern is that the tendon is most stiff and tender at the start of the day or at the start of training, and that it “warms up” during activity, only to be more irritated afterwards or the next day.
Why can light and laser make sense for tendon injuries?
PBM is based on the fact that red and near-infrared light is absorbed in cells and affects energy metabolism and signaling substances. In laboratory and animal studies, there are signs of increased ATP production, changes in inflammation markers or ROS, as well as an effect on calcium signals. These signals can trigger processes that are related to tissue repair.
In tendon tissue, the goal is rarely “rapid healing” in a few days. It is more often about creating better conditions for the tendon to tolerate gradually increasing load while the irritation decreases. PBM is therefore most relevant as a supplement: something that can be used alongside exercises, load management and possibly clinical treatment.
PBM also has an important practical advantage: it is non-invasive and generally associated with few side effects when used correctly and with respect for safety.
What does the research say about PBM for the Achilles tendon?
The biological explanation sounds promising, and some smaller studies have shown positive findings (e.g. changes in inflammation markers or pain during activity). At the same time, several systematic reviews and meta-analyses indicate that the overall clinical effect of Achilles tendinopathy is uncertain and that the results are mixed.
This does not mean that PBM “does not work”. It means that we cannot promise a clear, consistent extra effect for everyone when compared to control treatment. For many, the most realistic thing to do is to use PBM as an experiment for a limited period, while sticking to the treatment that has the best documentation: progressive training of the calf and tendon.
A large part of the differences between studies is about dosage, wavelengths, treatment frequency and whether PBM is given alone or together with exercises. Tendons appear to respond to “appropriate” doses, while very high doses may be less helpful because the response is biphasic (too little may be too weak, too much may dampen the response).
Below is a simplified overview of typical parameters seen in the literature when treating the Achilles tendon with laser/PBM. The numbers vary, and this is precisely part of the explanation for why the evidence can be difficult to gather.
| Parameter | Typical interval in studies | Practical significance |
|---|---|---|
| Wavelength | approx. 650 to 980 nm | Red light is more superficial, near-infrared reaches deeper into tissue |
| Dose per point/area | often a few joules per point or a few J/cm² | “Little but often” is frequently used for tendons |
| Duration | approx. 30 to 270 sec per point/area | Depends on the unit’s power and treatment area |
| Frequency | typically 2 to 4 times a week for several weeks | Single treatments are rarely enough for chronic problems |
A practical protocol at home: this is how you can approach it
If you want to test laser/PBM against Achilles tendon problems, it makes sense to do it systematically so you can assess whether it actually helps you. Rather start conservatively and adjust slowly.
Choose one clear area to treat: either the most tender part in the middle of the tendon or the area close to the heel bone. Many experience that the tendon is tender over a “band” of several centimeters, so it may be relevant to treat 6 to 10 cm of the tendon’s length with calm scanning or several stationary points.
Stick to a fixed rhythm in the beginning, preferably 3 times a week for 2 to 3 weeks, before assessing the effect. Feel free to write down briefly: morning pain, pain during walking/training and reaction the day after.
The most important thing is that the treatment does not become an excuse to “push through” with a load that the tendon is not ready for.
- Placement: treat along the tendon where you are most tender to the touch
- Contact: preferably use direct skin contact or very close to the skin (according to the manual for your device)
- Technique: stationary points or slow scanning, so that the entire irritated area is covered
- Frequency: 3 times a week in the beginning
- Short and calm
- Consistent rhythm
A practical benchmark is that the treatment should preferably be experienced as pleasant. If you experience a clear deterioration that lasts more than 24 hours, it is a signal to turn down the duration, intensity or frequency.
Where on the Achilles tendon should you treat?
In mid-portion tendinopathy, the tenderness is often 2 to 6 cm above the heel bone. In insertional problems, it sits closer to the heel bone, and there may also be irritation in the bursa or surrounding tissue.
Always treat based on symptoms and palpation (tenderness), not just based on where you “think” the problem is. Some also have tenderness in the calf muscles, and there PBM on musculature on the muscle belly can feel relieving, but it does not replace targeted tendon loading.
One sentence that often helps in practice: Treat where it hurts and where the tendon feels irritated, but train the entire chain from foot to hip.
Combine light therapy with load management and exercises
The most stable way out of Achilles tendon problems is typically a planned, progressive strength and tendon training. The classic is eccentric calf training, but many also do well with heavy slow strength (HSR) or a combination, as long as the progression is reasonable.
Pain during training may well be acceptable, but it must be controlled. Many clinical guidelines use a “traffic light” mindset: a little pain during training is ok, but pain must fall back to baseline within 24 hours.
- Green zone: slight pain during exercises, calm level the day after
- Yellow zone: more tenderness, but acceptable function, requires adjustment of volume
- Red zone: clear deterioration the next day, reduced walking, night pain, turn down and get assessed
If you use PBM, it can fit in well right after training or on rest days, because then you have a stable rhythm. The most important thing is that the exercise part does not become random.
Choice of wavelengths and equipment: what does it mean?
In tendon problems, it makes sense to think in depth. Red light around 650 to 660 nm is often associated with more superficial effects, while near-infrared light around 810 to 980 nm is typically used when the goal is deeper tissue such as tendons and muscles.
Many home units combine several wavelengths precisely to hit both surface and depth. Heat Sense works with CE-approved light therapy and laser therapy devices, and several of their solutions combine red light (around 650 nm) and infrared light (around 810 and 980 nm). This makes it practical to treat an area such as the Achilles tendon, where there are both superficial and deeper tissue layers.
Delivery from stock in Denmark and clear documentation for CE approval may also be relevant when assessing equipment for home use, because it says something about both logistics and product requirements.
Safety, typical reactions and when you should be extra careful
PBM is usually well tolerated. Some feel slight warmth, a brief redness of the skin or a transient change in the pain experience, especially if the area is already very irritated. It is rarely dangerous, but it is a signal to adjust.
Always avoid light directly in the eyes, and follow the manufacturer’s instructions. In case of pregnancy, cancer, photosensitive medication or if you have an unclear diagnosis, it is wise to talk to a doctor or therapist before you start.
- Eyes: avoid direct exposure, use protection if recommended
- Cancer: get medical advice before use near active areas
- Unexplained pain: in case of sudden swelling, heat, fever or severe night pain, you should be assessed
When does it make sense to get help, and what can PBM be supplemented with?
If you have had symptoms for more than 6 to 12 weeks without progress, or if you cannot control the load without relapsing, an assessment by a physiotherapist or sports professional clinician is often a good investment. They can help distinguish between mid-portion and insertional problems, assess calf strength, ankle mobility, foot function and training volume.
Some also benefit from supplementary treatment methods. Shockwave (ESWT) has overall better documentation for Achilles tendinopathy than ultrasound and PBM, and may be relevant if training alone does not move enough. Tape, heel elevation for a period and adjustment of shoes can also be useful, especially for insertional problems.
If the goal is to use PBM wisely, the most robust strategy is to make it measurable: agree with yourself which 2 to 3 things should get better (e.g. morning pain, pain on stairs, reaction after running), and give it a realistic test period while you continue with progressive training and reasonable load management.
