Updated: May 27
This article busts the myth that there are “micro-tears” in your tendon when you have Achilles tendonitis and that the pain and stiffness when you get out of bed in the morning are due to your tendon retearing when you put your weight on it. Remember, if you need more 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 our articles.
In this article:
We’ve also made a video about this:
Over the years, I’ve had quite a few patients with Achilles tendonitis or tendinopathy who told me they were scared of tearing their Achilles tendon by doing normal, non-strenuous activities such as walking.
When I asked them why, they told me that they had heard or read somewhere that they had “micro-tears” in their Achilles tendon and that this is what’s causing them pain. This is simply not true. The research into Achilles tendinopathy is quite advanced and clearly shows that it is caused by changes in the structure of the tendon, NOT tears. Yes, you can tear your tendon, but this is a totally different injury and actually not that common.
Micro-tears vs. micro-damage
When you exercise, it causes micro-damage (not micro-tears) in your tendon. This is natural and happens in all people; it signals to your body that the damage has to be repaired, and then your body repairs the damage so that the tendon is now a little stronger than before. The same happens in our muscles, bones, and joints, and this is how exercise makes us fitter and stronger.
This micro-damage is at a cellular level (single cells are injured), so nothing is torn.
Achilles tendinopathy is mostly caused when you repeatedly don’t allow your tendon enough time to repair the micro-damage between bouts of exercise and/or other activities that work the tendon hard. The unrepaired micro-damage then accumulates, and the tendon eventually changes its structure (still not torn!) in the area that is affected.
What it looks like under a microscope
The first picture is of a healthy Achilles tendon.
Tendons are made up of lots of collagen fibres that are aligned in parallel, and that’s what makes a tendon so strong. It’s easy to snap one piece of string, but quite a bit harder to snap ten pieces of string in one go; the same principle applies here.
You also find some cells (where the arrow is pointing) and a bit of fluid-like substance between the collagen fibres.
The second picture is what it looks like when you start to develop a tendinopathy.
The collagen fibres have moved a bit further away from each other, and there are more cells and fluid than usual between them.
The last picture is what full-blown Achilles tendinopathy looks like.
The collagen fibres in the affected area are now all disorganised and not in parallel anymore. There is also a lot more fluid between the fibres. But nothing is torn in there.
It’s important to note that it is usually only a small portion of the tendon that is affected and that the rest of the tendon is usually still strong and healthy.
Why is it so painful to walk?
When you have Achilles tendonitis or tendinopathy, your tendon can feel very painful or stiff when you try to walk first thing in the morning or after sitting still for a while. This stiffness and pain are the result of even more fluid that has seeped in between the collagen fibres due to you lying or sitting still for several hours. As you move, your circulation improves, and the fluid dissipates. That’s why your pain and stiffness usually decrease after a few steps.
How to turn things around
So, if you have Achilles tendinopathy, the structure of the injured part of your tendon has changed (from parallel collagen fibres to less organised collagen fibres), but you can turn this around.
The way to do this is twofold:
Giving the tendon relative rest, i.e. keeping it active but at a level that doesn’t increase your pain.
A strength training programme (typically going up and down on your toes) that starts at a difficulty level that your injured tendon can tolerate and that becomes gradually more difficult as the tendon gets stronger.
How we can help
Need more 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. 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.
About the Author
Van Der Vlist, A. C., et al. (2021). "Which treatment is most effective for patients with Achilles tendinopathy? A living systematic review with network meta-analysis of 29 randomised controlled trials." British Journal of Sports Medicine 55(5): 249-256.