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Why do I have a lump in my Achilles tendon?

Updated: 4 days ago

Have you noticed a painful lump in your Achilles tendon? That lump is a tell-tale sign that you’ve likely got Achilles tendonitis or tendinopathy. In this article, I explain what happens to your tendon when you injure it and why it develops this lump. Remember, if you need help with an Achilles injury, you're welcome to consult one of our team via video call.

Injured runners sitting on a track inspecting his Achilles tendon and asking: "Why do I have a lump in my Achilles tendon?"

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:

I also explain it in this video:

What the Achilles tendon normally looks like and what it does

The Achilles is a thick, broad tendon that attaches the calf muscles (gastrocnemius and soleus) to your heel. When the calf muscles contract, they pull the Achilles tendon tight, which in turn makes your foot point downwards. This is the action that allows you to push off when you walk, run, and jump.

If you look at a healthy Achilles tendon under a microscope, you’ll notice that it's made up of thousands of collagen fibres that are packed closely together in parallel, with very little space between them. These fibres are all aligned in the same direction. This is important because it’s what makes the Achilles tendon so strong!

Healthy Achilles tendon with fibres closely packed and small cells.

Do you remember playing with string at school? If you had a single thread, you could easily snap it. But as soon as you put a few pieces of string next to each other, it was nearly impossible to break.

Healthy Achilles tendons are extremely strong and stiff. Unlike muscles, we want tendons to be stiff, because they work better that way. (This is why doing stretches for Achilles tendinopathy is really not that useful.)

If you look closely at the picture above, you’ll notice that there are also a few small cells in the tendon.

What happens in your Achilles tendon when you injure it?

The pictures below shows what happens in the Achilles tendon when you injure it.

Picture B is of a tendon that has been sore for a few days. Can you see that the collagen fibres are now starting to move away from each other and that there’s more white stuff in between them? There are also more cells in the tendon than usual.

Microscopic image of an injured Achilles tendon. The fibres are moving away from each other and there are many more cells in the tendon.

Picture C is a microscopic image of what a tendon looks like when it has been sore and injured for several months. The collagen fibres are no longer aligned next to each other; they're all jumbled up like cooked spaghetti in a bowl, and you now have large cells (of the wrong kind).

This tendon has been injured for a long time. The fibres are no longer aligned next to each other, and the cells have changed shape and size.

If you look at the tendon on an ultrasound scan, you’ll also notice that there are several small blood vessels growing into the painful part of the tendon. Healthy tendons don’t have blood vessels growing into them.

The end result of all of these changes (fibres moving further apart, cells becoming bigger, blood vessels growing in) is that your tendon develops the lump that is associated with tendonitis. The tendon is now softer and more elastic and doesn’t work as well as before.

How to get rid of the lump in your tendon

Achilles tendinopathy or tendonitis develops when you over-strain or overload your tendon. The only way to help your tendon to recover and get rid of the lump in your Achilles is through managing the load that you put through your tendon on a daily basis.

What do I mean with load? Load refers to all the work you ask the tendon to do in a day. This includes walking, running, jumping, heel raise exercises, and ANY other activity that uses the Achilles.

That’s why our first step when treating Achilles pain is always to have an in-depth discussion with our patients to get a complete picture of their normal training regime and their other daily activities such as work. This doesn't mean that you necessarily will have to stop all your training; most of the time we find that we can just adjust the volume or intensity to a level that allows your Achilles to recover while you maintain your fitness.

Rest alone isn't helpful either. It may decrease the pain a bit, but it doesn’t actually strengthen the tendon. You need to do carefully graded strength training exercises to get the body to replace the injured tendon cells with new strong ones that are packed closely together once again. It’s a similar process to going to the gym to build bigger and stronger muscles.

Follow this link to read more about our expert online physio service for treating Achilles tendon pain.

This is also why passive treatments like massage and dry needling aren’t really that useful for this condition. Yes, it may make your calf muscle feel more relaxed and less painful, but massage doesn’t change anything inside the tendon. Just like you can’t massage your muscles stronger, you also can’t massage the lump away! The cells and fibres have to change, and that can only be done through load management and strength training.

What exercises should you be doing? There is no one-size-fits-all. I have to adjust what I prescribe for every patient, taking their current tendon strength, their normal training regime, etc. into consideration. What works for one person’s Achilles tendon may overload the next one's tendon.

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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Maryke Louw

About the Author:

Maryke Louw is a chartered physiotherapist and holds an MSc in Sports Injury Management. You can follow her on LinkedIn, Facebook, Twitter, and Instagram.



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