Achilles tenosynovitis is the incorrect name for when the sheath that surrounds your Achilles tendon gets injured. Sports physio Maryke Louw explains how the treatment for this injury often goes hand-in-hand with the treatment for an injured Achilles tendon, and why the correct name for it is Achilles paratenonitis. 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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Anatomy of the Achilles sheath
When we look at the back of the calf, you have your two calf muscles – gastrocnemius and soleus – merging into the Achilles tendon, and then the Achilles tendon attaches onto the heel bone. There’s a sheath around the Achilles tendon called the paratenon.
This sheath is very flexible and can stretch anything from 2 cm to 3 cm. It acts like a tunnel in which the Achilles tendon can move without catching against bones, muscles, and other tendons.
The sheath has quite a few veins and arteries that supply the Achilles tendon with blood. It also has nerve endings.
What the Achilles paratenon doesn’t have is synovial fluid. It is therefore incorrect to refer to an injury of the Achilles paratenon as “tenosynovitis”, because the “-synov-” bit refers to a sheath that does contain synovial fluid.
So, the correct terms for an injury to the sheath are Achilles paratenonitis or Achilles paratendinopathy. The two terms are often used interchangeably, but the former implies inflammation (which applies more to the acute stage), and the latter implies very little, if any, inflammation (more relevant in chronic cases).
What is Achilles paratenonitis?
Achilles paratenonitis occurs when something irritates this sheath that surrounds the Achilles tendon, and now the tendon cannot move freely in the sheath.
It can be caused by anything that compresses or stretches it too much. Examples:
a blow to the tendon
the back of a shoe rubbing against the tendon
a sudden increase in training, e.g. a ramp-up in speedwork or hill running sessions
a change of footwear that stretches the tendon more (usually shoes/sandals that are flatter than the previous ones)
aggressive stretching of the tendon.
Like with an Achilles tendonitis, Achilles paratenonitis can be acute or chronic. The one is not more serious than the other, but the symptoms are somewhat different.
Acute Achilles paratenonitis
This refers to an injury that happened less than three months ago.
Inflammation usually sets in shortly after the injury happened. This causes fluid to accumulate in the sheath, which causes swelling, pain, and a feeling of stiffness, and the Achilles tendon cannot move freely.
You may also experience crepitus – a crackling or popping sensation in your Achilles tendon when you move it.
Chronic Achilles paratenonitis
If the injury has been present for more than three months, the swelling tends to settle down, and you don’t have that acute inflammation anymore.
The paratenon starts thickening, and you get adhesions between the sheath and the tendon, which prevents the tendon from moving freely.
At this point, the crepitus usually also decreases quite a bit, and it is just the discomfort when you use your foot that remains.
Diagnosis of paratenonitis
There are some challenges when trying to diagnose Achilles paratenonitis. The injury may have occurred simultaneously with an injury to the Achilles tendon, and probably due to the same cause. Also, some of the symptoms may be similar to those of other conditions like heel bursitis and gout.
But these challenges are not insurmountable. An experienced physiotherapist will listen carefully to the patient’s injury history to piece together what happened.
And there are some clues that a physio can look for to tell them whether this is Achilles paratenonitis and not, for instance, Achilles tendonitis:
The swelling of acute paratenonitis is diffuse – spread over an area – whereas the swelling of tendonitis is concentrated in a little nodule. One has to also rule out an Achilles tendon rupture if you have diffuse swelling.
When you move the tendon, i.e. by moving your foot up and down, the swelling caused by paratenonitis stays in the same place, whereas the nodule caused by tendonitis moves with the tendon.
With paratenonitis, the pain and discomfort caused by activity (e.g. going for a walk) tend to increase as the activity progresses, whereas these symptoms tend to decrease with tendonitis. A partial Achilles tear may also cause pain that increase with activity.
In the acute phase of paratenonitis there might be crepitus, which will not be present if you only have tendonitis.
Acute paratenonitis may cause some redness of the skin, and it can feel hot to the touch (but this can also be true of gout or heel bursitis). Your family history and how the injury started will help distinguish between the them.
Ultrasound scans and MRI scans can pick up Achilles paratenonitis, but it is usually possible to arrive at a diagnosis in most cases without having to have a scan.
Of course, it is quite likely that you might have both Achilles paratenonitis as well as an injury to the tendon itself, in which case the symptoms for both should be present, and an experienced physio will pick up on this. And, as we shall see in the next section, the treatment for Achilles paratenonitis and an injured Achilles tendon follow the same principles anyway.
Achilles paratenonitis treatment
The rehab of Achilles paratenonitis broadly follows the same three-step process as for the rehab of Achilles tendonitis or tendinopathy. And that's why it's not that difficult to treat both conditions at the same time.
1. Allow your paratenon to calm down
A big mistake that some injured people make when they are super motivated to get better is to visit Dr Google and then say “Ah, I’ve got to do these stretches and these exercises!” and start doing them right away.
But that injured area is overworked, and it needs a bit of a break so that your body can get rid of everything that's been irritating it and just calm it down.
So, avoid rehab exercises during the first few days. Don't be too aggressive with anything, and get guidance from a physiotherapist so that they can help you understand when the correct time is to start your rehab exercises.
In the meantime, there are some things you can do to help reduce the load on the injured tendon and/or sheath to allow it to calm down more quickly:
Don’t just sit there and do nothing. Your injury needs some movement and some circulation. Rather, reduce your activities to levels where they don’t make the pain and/or discomfort worse. So, if you usual 5 km run is painful towards the end, reduce the distance for now. If your powerwalking hurts, walk slower. Or switch from running/walking to cycling or swimming for the time being. We explain this approach of “relative rest” in more detail here.
Avoid flat shoes or sandals – they put extra stretch on your Achilles tendon and on the paratenon. Most types of running shoe have a bit of a heel to them, and/or you could get some heel wedges to put into your shoes (both sides) to raise your heels a bit.
Here are some examples of various types of heel wedges available on Amazon:
In the acute phase of Achilles paratenonitis, anti-inflammatory medication might be useful. Excessive inflammation might lead to those adhesions that restrict the movement of the tendon later on.
In our articles about injuries to the Achilles tendon itself, we warn against anti-inflammatories, but this doesn’t apply in the case of paratenonitis. If you have both conditions at the same time, the benefits of anti-inflammatory medication still outweighs the risk and it’s worth taking a short course during the acute stage.
Ask your doctor before you use anti-inflammatories, because there might be reasons why they wouldn’t be suitable for you.
2. Identify the cause and address it
If you don’t want the injury to rear its head again, you have to address the cause. Knowing what caused it might also help to inform how to adapt your activities in Step 1 above.
We’ve already touched on some causes above, but usually it boils down to:
Overtraining – either general overtraining or ramping it up too quickly.
Biomechanics (how your legs and feet move when you run). A physiotherapist can assess this and help you understand whether there are things that need to be addressed.
The wrong shoes or changing from heeled shoes to flat shoes or sandals.
3. Gradual loading
With Achilles paratenonitis, the calming down phase shouldn’t last more than a few days – maybe a week or two at the most – and then we have to start getting the paratenon used to load again, which then gradually increases.
The way that you increase load on the paratenon is the same as you would do for Achilles tendinopathy. Typically, this involve doing calf raises (going up on your toes), and there are various ways and combinations in which you can do and increase these.
However, the aim of the exercises for Achilles paratenonitis (if you have this injury exclusively) differ somewhat from that of Achilles tendonitis rehab exercises. With the latter, the aim is to strengthen the tendon; with the former, it's to gradually increase the load to see what it can tolerate at this point, because it won't be able to tolerate high loads initially. And this will help you to avoid flare-ups if you do it in a very step-based manner.
The good news is that the recovery time for exclusive paratenonitis is usually shorter than for Achilles tendinopathy, because you don’t have to rebuild your strength. If you can calm it down properly in that initial stage, you can actually reload it relatively quickly, and your recovery time can be a few weeks or maybe a couple of months.
But if you have Achilles tendinopathy in combination with paratenonitis, it will obviously take longer, because now you've got to also treat the Achilles tendon.
This phase of your rehab is also about increasing your usual activities gradually, i.e. the volume and intensity of your running, your walking, or your cycling.
What about massage for Achilles paratenonitis?
If you’re going to get your inflamed paratenon massaged in the acute phase, it will likely just increase your inflammation.
Some people might think that you can break down those adhesions in the chronic phase with friction massage. There’s no high-quality research to support or refute this claim. So, you can try it if you like but make sure you monitor your symptoms. If your pain fails to settle down or it even increases after three sessions, I would stop the treatment.
What if rehab doesn't work?
Sometimes the above treatment won’t work, even if you’ve followed all the steps diligently and didn’t skimp on or overdo your rehab exercises. If this is the case, there are some other options to consider.
Injections
Corticosteroid injection
A corticosteroid injection can be used to settle down chronic inflammation that doesn’t want to settle down.
The injection has to go into the sheath itself, not into the tendon. This has to be done by a skilled professional who uses ultrasound so they can see exactly where the needle is going.
You have to be quite careful with your rehab for a few weeks after that to make sure that you strengthen everything up properly, because there's a risk of tearing your Achilles tendon after you’ve had steroids.
High-volume injection
A high-volume injection is where they use a high volume of fluid to try and break down those adhesions that form in cases of chronic Achilles paratenonitis.
Surgery
Surgery is an option for chronic cases of Achilles paratenonitis that don’t want to calm down and you've had it for a long time and it's stopping your progress. But you must have tried the other things first and have had scans to show that this is actually your problem.
This usually involves keyhole surgery to loosen the Achilles tendon from the adhesions that have formed in the chronic phase.
There are also two recently developed surgical procedures called Tenex and Tenjet, which are minimally invasive, and they seem to work really well and have a quicker recovery.
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.
References
Ricci, V., Mezian, K., Chang, K. V., Tamborrini, G., Jačisko, J., Naňka, O., & Özçakar, L. (2024) “Ultrasound-guided injection of the achilles paratenon: A cadaveric investigation” Foot and Ankle Surgery 30(4): 313-318.
Chimenti, R. L., Stover, D. W., Fick, B. S., & Hall, M. M. (2019) “Percutaneous ultrasonic tenotomy reduces insertional Achilles tendinopathy pain with high patient satisfaction and a low complication rate” Journal of Ultrasound in Medicine 38(6), 1629-1635.
Pereira, H., Vuurberg, G., Stone, J., & Lui, T. H. (2017) “Ankle tendoscopy: state of the art” Journal of ISAKOS 2(6), 332-338.
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