Patients often ask me whether they should get a TENS unit for their Achilles tendonitis. Well, it depends on whether you want to use it for pain relief or to speed up healing. In this article, I look at what the research says about this, and I give some practical tips on how to use a TENS unit for Achilles tendonitis. Remember, if you need help with an Achilles injury, you're welcome to consult one of our team via video call.
The terms tendinitis, tendonitis, tendinosis, and tendinopathy mean the same thing for all practical purposes, and we use these interchangeably in most of our articles.
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TENS (or transcutaneous electrical nerve stimulation) can help people with Achilles tendonitis in potentially two ways. It might help to reduce the pain caused by the injury, and it might help the injury to heal faster. So, let’s look at what the research says in each case, and then I will give some practical tips on how to use a TENS unit for Achilles tendonitis.
TENS for Achilles tendonitis pain
The people in the white lab coats have done quite a lot of research on TENS for both acute and chronic pain.
The consensus is that, yes, TENS is effective for pain relief while it is being applied; i.e. while you’re hooked up the machine, it brings pain relief. In some cases, the pain relief also lasts for a few hours after the TENS session.
However, there is no long-term effect. Using TENS consistently for days on end won’t get rid of your Achilles pain.
So, TENS might be helpful if you have a very painful Achilles tendon and you don’t want to take medication, or medication doesn’t do the job. But TENS won’t work as a standalone treatment – it’s not a silver bullet for finally getting rid of your Achilles tendon pain.
TENS for Achilles tendonitis healing
I was quite surprised to have come across only three research studies that investigated whether TENS is effective for healing damaged Achilles tendons. To make things even more tricky, their findings were contradictory, and there is a possibility that some of the researchers were biased.
Let’s look at what they found.
1. TENS for healing after Achilles surgery?
In 2005, a group of researchers wanted to see whether TENS would help an Achilles tendon to heal faster after surgery.
They took 18 people who had had Achilles tendon surgery and split them into two groups of nine each. One group had TENS treatment – 30 minutes per day for five days – and the other group did not receive TENS treatment.
When the researchers analysed the Achilles tendons afterwards, they found that the tendons of the group that received the TENS treatment produced more collagen (the main building block of tendons), they were more dense, and they seemed to heal more quickly.
However, this study had a high risk of bias (RoB) when I looked at the factors according to which you rate a study's quality. There is a summary of my RoB assessments for this and the following two studies at the bottom of this article.
2. Trying TENS on rats
In a 2015 research study, researchers took 60 rats and damaged their Achilles tendons. They then gave 30 of the rats TENS treatment and analysed the Achilles tendons of all 60 rats.
In this study, they found that the TENS treatment actually inhibited collagen growth, and the Achilles tendons didn’t recover as well as those that did not receive the treatment.
But again, this study also had a high RoB. So, we have to careful not to jump to conclusions.
3. “TENS” for rats – this time with needles
The most recent study on Achilles tendons is from 2021. This study wasn’t technically TENS, because the researchers delivered the current into the tendon via needles instead of electrodes on the skin.
This time, they took 34 rats and damaged their Achilles tendons. They then delivered the electrical current to 17 of the rats by inserting needles into their tendons.
This produced a higher collagen density and stronger collagen in the rats whose tendons got the “TENS” treatment.
This study had a medium RoB. So, better than the previous two, but there were still some concerns.
What can we conclude from these three studies?
I'm not convinced that TENS helps that much for Achilles tendonitis healing.
But neither do I think that it inhibits healing. From personal experience, I've not seen massive differences in my patients who use TENS versus the ones who don't when it comes to how fast their Achilles injuries heal.
We’re going to need higher-quality studies on humans to get certainty either which way.
So, even if TENS doesn’t speed up healing, it can be useful if you have a very painful Achilles tendon, or it's just driving you nuts certain times of the day.
How to use your TENS unit for Achilles tendonitis
TENS placement for Achilles tendonitis
The research on pain science shows that it doesn't really matter where you place the electrodes, as long as the current runs through the painful area.
So, for an Achilles tendon, there are two obvious options:
Place the electrodes above and below so that the current runs vertically along your tendon.
Place the electrodes either side of the tendon so that the current runs across your tendon.
💡Top tip: Because of their shape, it can be tricky to get the larger electrodes to stick properly on the Achilles tendon. In my experience, the smaller ones stay on better.
I found these two TENS units on Amazon as examples of what I’m talking about:
Intensity
The research shows that there's no ideal TENS intensity.
The sweet spot seems to be:
an intensity level that is as high as you can tolerate without it causing you pain, and
a level that doesn’t cause muscle contractions – if your muscles twitch, dial the intensity down a bit.
💡Top tip: If your TENS unit has a setting that automatically varies the duration and frequency (or rhythm) of the pulses during a session, use it. Your body will get used to the TENS current if it is set at the same rhythm or frequency all the time, and then it will be less effective. Same as when you notice a noise at first, but if it persists, it becomes something in the background that you’re not really aware of.
How often to use TENS
The research shows that it doesn't really matter. You can use it for as long as you like; it's not one of those things that you can overdo. So, use it as much as you feel you need it.
TENS side effects?
You don't want a TENS current to interfere with an electronic implant such as a pacemaker. So, avoid using it over an implant that relies on another current to function. But if you're using it on your Achilles tendon it should be okay.
Other possible minor side effects:
You can get a skin irritation if you leave the electrodes on for too long.
Some people might get rashes if they’re allergic to the electrodes.
How we can help
Need help with your Achilles injury? You’re welcome to consult one of the team at TMA online via video call for an assessment of your injury and a tailored treatment plan.
We're all UK Chartered Physiotherapists with Master’s Degrees related to Sports & Exercise Medicine or at least 10 years' experience in the field. All of us have a wealth of experience working with athletes across a broad variety of sports and ranging from recreationally active people to professional athletes. You can meet the team here.
About the Author
Maryke Louw is a chartered physiotherapist with more than 20 years' experience and a Master’s Degree in Sports Injury Management. Follow her on LinkedIn and ResearchGate.
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