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Swollen Achilles tendon – Why does it swell and when can I exercise?

Updated: Oct 25

Whether it’s a good idea to exercise with a swollen Achilles tendon depends on why it is swollen or appears to be swollen. In this article, we explore some scenarios and explain what each of them means for doing exercise. Remember, if you need help with an Achilles injury, you're welcome to consult one of our team via video call.

Learn why your Achilles tendon is swollen and how to treat it.

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.

In this article:

  1. Why is my Achilles tendon swollen?

  2. Achilles “swelling” due to tendonitis

  3. Achilles swelling due to a tear or surgery

  4. How we can help

We've also made a video about this:

Why is my Achilles tendon swollen?

There are three main reasons why someone’s Achilles tendon may be swollen or appears to be swollen.

  1. Achilles tendonitis: In this case, it’s not really swelling; it is changes in the structure of the tendon that we’re talking about.

  2. The tendon has been partially torn or totally ruptured.

  3. Due to surgery, usually to fix a total rupture.

We’ll first deal with apparent swelling due to Achilles tendonitis, and then we’ll deal with swelling due to a tear or surgery.

Achilles “swelling” due to tendonitis

Although the tendon may indeed look and feel thicker or bigger than your healthy tendon on the other side, it's not actually true swelling.

Healthy tendon fibres are neatly arranged in parallel – this is what makes a tendon so strong.

Healthy tendon tissue viewed under a microscope with fibres running in parallel.
Healthy tendon tissue viewed under a microscope, with fibres running in parallel.

However, when tendinopathy sets in, some of the fibres lose their parallel structure and become disorganised, which reduces the strength of the tendon. There is also an increase in fluid that fills the space between the disorganised fibres, and this creates the impression of swelling and maybe a feeling of stiffness.

When you have a tendinopathy, the collagen fibres in the affected area are disorganised with more fluid between them.
When you have a tendinopathy, the collagen fibres in the affected area are disorganised, with more fluid between them.

People often experience and describe this as a lump, and we have an article that explains in much more detail why there is a lump in your Achilles tendon.

To answer the question of whether it is safe to exercise in this instance: It is safe and actually essential to exercise the calf muscle and the tendon, because the tendon won’t regain its strength if you just take it easy and don’t strengthen it back up.

Just resting the tendon will increase the risk of re-injury, even after the initial pain has gone. Here’s our article that explains the type of exercises you should be doing for Achilles tendonitis rehab.

Rehab exercises strengthen your Achilles tendon and reduce the swollen appearance, but they have to be pitched at the correct intensity.
Rehab exercises strengthen your Achilles tendon and reduce the swollen appearance, but they have to be pitched at the correct intensity.

Of course, it’s possible to overdo any exercise if one is not careful. At Treat My Achilles, we use the principle of “relative rest” to advise our patients on this. In short, this means that exercise shouldn’t cause you pain of more than 3 out of 10 (where 10 is severe pain) and that your tendon shouldn’t feel worse than before within the 24 hours after you’ve done the exercises.

This approach doesn’t involve only the rehab exercises but all your activities, including things like work and housework. You can read more about relative rest for Achilles rehab here.

In summary: For Achilles tendonitis, it is safe and important to exercise while your tendon still looks swollen. However, the exercise has to be pitched at the correct level for your tendon’s current strength and sensitivity.

Achilles swelling due to a tear or surgery

In these cases, we are indeed dealing with true swelling – the kind you get when soft tissue fibres have been torn or cut.

There would have been some internal bleeding, and then inflammation sets in, which causes the swelling. Contrary to popular belief, inflammation is a good thing in these instances, because it plays an essential part in the healing process where dead and damaged cells are taken away and new cells are deposited.

Unfortunately, there’s no one-size-fits-all answer about exercise under these circumstances, as people’s pain levels and the strength of their torn and post-op tendons differ.

What is certain is that, once your tendon fibres have grown together sufficiently, you will have to do the same type of rehab exercises described above to get the tendon back to its former strength. Your surgeon or a physiotherapist should be able to advise you on when to start with these.

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However, you can aid your tendon’s recovery in the meantime by doing cross-training. What you can safely do after a rupture or surgery will depend on your stage of healing and your physiotherapist can advise on this.

Cross training supports healing and helps reduce Achilles tendon swelling by improving the body's circulation.
Cross-training supports healing and helps to reduce Achilles tendon swelling by improving the body's circulation.

In addition to maintaining cardiovascular fitness and keeping the rest of your body in shape, cross-training will increase your blood circulation, which will speed up your Achilles tendon’s healing process by flushing away the bad stuff and bringing in nutrients and oxygen.

In summary: For Achilles tendon tears or after surgery, the stage of healing your tendon is in will determine with what exercise you can start, and when. The amount of swelling doesn’t really impact the decision.

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.

Meet the TMA physios

We're all UK Chartered Physiotherapists with Master’s Degrees related to Sports & Exercise Medicine. But at Treat My Achilles we don't just value qualifications; all of us also have a wealth of experience working with athletes across a broad variety of sports, ranging from recreationally active people to professional athletes. You can meet the team here.

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Alison Gould

About the Author

Alison Gould is a chartered physiotherapist and holds an MSc in Sports and Exercise Medicine. You can follow her on LinkedIn, Facebook, Instagram or Twitter.


  1. Cook JL, Rio E, Purdam CR, et al. “Revisiting the continuum model of tendon pathology: what is its merit in clinical practice and research?” British Journal of Sports Medicine 2016;50:1187-1191.

  2. Maffulli, N., et al. (2022). "Slowed-Down Rehabilitation Following Percutaneous Repair of Achilles Tendon Rupture." Foot Ankle Int 43(2): 244-252.

  3. Silbernagel, K.G., Thomeé, R., Eriksson, B.I. and Karlsson, J., 2007. "Continued sports activity, using a pain-monitoring model, during rehabilitation in patients with Achilles tendinopathy: a randomized controlled study." The American Journal of Sports Medicine, 35(6), pp.897-906.

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