Achilles Tendinitis Treatment Science

Evidence-based guidelines for the fastest possible recovery

Paul Ingraham • Nov 30, 2024 • 35m read

Achilles tendinitis is one of several common repetitive strain injuries (RSI). The giant tendon can be stressed until it becomes acutely irritated and then, in some people, it stubbornly refuses to heal — either because it keeps getting re-irritated, and/or because it’s just naturally difficult for tendon to recover… and that phenomenon is worse in some people. Not all tendons are created equal. And tendons are very biological. Vulnerability to tendinitis is powered by genetics and pathology and lifestyle, by fitness and metabolic health, as much as by overloading.

All of the well-known RSIs have a lot in common. I give more detailed information about the nature of the beast in a separate guide (see Guide to Repetitive Strain Injuries). That article dives deep into questions like: Are RSIs really inflamed? Do we get them because of things like biomechanical asymmetry, poor ergonomics, a wonky gait? And much more. This article is a self-help guide to Achilles tendinopathy home remedies (but with enough references for pros as well). And what is true of the Achilles tendon is also true for most other tendons, most of the time. Achilles tendinitis does a good job of representing other kinds of tendinitis.

Achilles tendonitis recovery time

How long will it take? The short answer is that a typical case of Achilles tendinitis will take about three months to get clear of. Six months is considered unusually stubborn.

The real answer contains a lot more “it depends.” Data is thin and messy. Are 10% of athletes ready to “return to sport” (RTS) after 12 weeks? Or 85%? It depends on which study you read!1

Ultimately, it will take as long as it takes, and there’s a huge range, from a few weeks to literally years.

The popular perception is that tendons don’t heal well, like cartilage or fingernails. One expert source claims “the less blood delivered, the longer it takes for tissue to heal,” but there’s much more involved in this equation, and the truth is in the middle: tendon definitely can heal, but it’s not exactly quick about it (like the mouth, say, the fast healing champ of the human body).

There are poorly understood vulnerabilities and complications that can slow down recovery and increase the risk of re-injury.2 In hundreds of elite soccer players, 27% of all cases were do-overs, and that rate spiked to 31% in players who opted to go back to the field sooner, compared to just 13% in those who took their time.3 So even if you can get back to the action in six weeks… maybe give it nine? And there’s your first evidence-based rehab tip.

Blue outlines the whole Achilles tendon, and red the typical location of Achilles tendinitis pain.

Can tendon truly heal? The tissue regeneration question

Tendon injuries do not seem to heal well, and we do not know why this is. It has often been suggested that the problem is slow tissue turnover. As with cartilage, maybe we just lack the ability to replace cruddy tendon tissue with nice fresh stuff. But no one really knows and it’s surprisingly hard to know.

In 2013, Heinemeier et al. published what is surely the coolest tendon study that has ever been or ever will be: they figured out a particularly sensational method. The atomic signatures of the era of nuclear bomb testing are still written into the tendons of people who were alive at the time, trapped like bubbles of ancient air in an ice core.4

So there was basically no turnover in tendon tissue in adults. But there was a catch: they only looked at healthy tendons in that first study. In 2018 they did it again, but they compared both healthy and unhealthy tendons … and got a surprise: un-healthy tendon does get recycled. •mind blown•5

This is a hard result to interpret, but the authors have two ideas:

1. Tendon disease causes tendons to start recycling and regenerating tissue, trying to cope with the load. Success not guaranteed! And then, much later, the symptoms kick in.
2. Tendon turnover could actually be a cause of tendinopathy. For unknown reasons, the tendon is inappropriately trying to reinvent itself, and it’s a vulnerability (or a sign of another one) rather than an adapative thing. Eventually, the churning of tissue causes disease. In this scenario, we would say that tendinopathy is caused by an excessively regenerating tendon. You could think of it as “unstable” tissue, and therefore more vulnerable to injury.

Patching the tendon

It appears that the body can lay down a fresh layer of connective tissue, so one model for this process is that a troubled tendon can be helped out by wrapping a “rotten” core in a fresh and fully functional outer layer. “Healing”! So at least there’s that.

The first rule of tendinitis treatment is to just accept that there’s no known method of actually speeding or facilitating that process. Accelerated/regenerative healing are not serious options for Achilles tendinitis. (More about high-tech regenerative treatments below.)

What should you take away from all this? Simple: we can put people on the moon, but we still don’t know how tendinopathy works.

Treating Achilles tendinitis at home

The bad news? Sports medicine and injury rehab science is surprisingly, depressingly primitive,6 and there is mostly no such thing as “advanced” treatment for Achilles tendinopathy (or any other tendinopathy).

The good news is that you mostly don’t need the “depressingly primitive” assistance of doctors, physical therapists, and other professionals. At their best, the pros are good rehab coaches and guides — but not even the best have any magic bullets for Achilles tendinitis, and a large percentage of their guidance can be replaced by an article like this. So you absolutely can treat Achilles tendinitis DIY style, relatively cheaply and safely. (And you can fail with the knowledge that a professional probably wouldn’t have made any difference.)

See my reviews of types of professionals who can help with chronic pain, and a tour of common problems with typical physical therapy.

Load management in principle

The basic template for all injury rehab is to “calm shit down” and then “build shit up,”7 also known as “load management.” That is, first you rest, soothe, comfort, reassure, protect … and then you gradually introduce easy, artificial challenges, and then more difficult functional ones, slowly “demonstrating” to your brain and tendons that painless function is possible and eventually required.

The challenge is to keep your tendons in the Goldilocks zone: stimulated enough to heal, but not so much that you re-irritate the tendon. It’s a challenge because the Goldilocks zone changes as you heal, and so you have to keep up with it… which is a bit error-prone. Many factors affect our vulnerability to load.8 This uncertainty is the main source of error in rehab: we can never be sure how much stimulation is enough or too much.

So bog standard rehab for tendinitis usually consists of:

• activity modification (avoiding excessive tendon stresses, taking it easy)
• exercise (building it up)
• limited steroid injections for pain control (an extremely popular option)

Ten years after doing this kind of rehab, 76% of about a hundred patients were back to normal, with no sign of serious consequences of the steroid injections.9 But 24% were not — after a decade! Those numbers tell a clear story: most people are probably eventually going to be fine with standard therapy, but clearly not everyone.

Don’t underestimate the importance of rest

If there’s a “trick” to load management, it’s that the initial resting phase is important — probably more important than most people realize.10 And the build-shit-up phase is slower and more baby-steppy than most people realize. Especially with &*!@# tendinitis.

It’s also largely just a matter of simply not interfering with natural healing by re-irritating it, so please really make sure you take it quite easy for a quite a while. Avoid spikes in tendon loading like the plague in the early stages.

But it’s not like you won’t use your tendons at all while taking it easy. There is work to do…

Stimulating new tendon growth: early mobilization

Exactly how to inspire the body to lay down that fresh layer is, of course, not totally clear. We know it’s possible, but it probably requires a just-right amount/kind of exercise stimulation that is impossible to be sure of.

In general it just means progressively loading the tendon, asking it to do its job a little more each week over many weeks: progressive training.

And what is its job? The major function of the Achilles tendon is that it’s a giant elastic that absorbs some energy during part of your stride, and gives some of it back during another part, kind of like regenerative braking in an electric car. Anything that doesn’t use that system won’t be very challenging/stressful to the tendon.

But you also can’t start out asking it to do its entire job, anymore than you send someone back to work the day after they’ve had a major surgery. One thing at a time. So you start out with easier, less functional challenges.

Initially, you focus on unloaded, pain free range of motion exercises or “mobilizations” — literally just flexing the foot up and down, or rolling the ankle around in circles, “pumping” the tendon and leg muscles gently, without straining it in the least. This is so easy it is compatible with rest. It is resting… but with gentle stimulation of the tissue while you rest. Use it or lose it!

After patiently doing plenty of that, you transition to the first obvious functional challenge: heel raises. Lots and lots of heel raises over time. Not many and very easy at first, but more and more intense over many weeks and months, eventually working up to fairly high loads and more serious challenges like eccentric training (see below).

And, as you go, you start to mix in more functional challenges, which mostly means walking and jogging, but in quite small doses initially.

Stop taking fluoroquinolones (or, for pity’s sake, do not start)

Fluoroquinolones (e.g. Cipro) are a class of antibiotics with particularly nasty side effects, lots of them, and in great variety. These drugs are “associated with disabling and potentially permanent serious side effects … can involve the tendons, muscles, joints, nerves & CNS.”11 But the most infamous side effect of fluoroquinolones? A 2.5× greater risk of Achilles tendinitis than the average healthy person, and a 4× greater risk of Achilles tendon rupture.12 Jebus. 😳

If you took fluoroquinolones any time for several months before you developed Achilles tendinitis, or had a rupture, then you can probably blame them for it. If you have Achilles tendinitis now, please refuse any prescription — it could make a bad situation much, much worse.

Isometric contractions for Achilles tendinitis

In a 2017, a high profile study suggested that isometric contractions are an effective treatment for Achilles tendinitis.13

Iso-what? Isometric contractions are non-moving contractions, so basically clenching. Isometric loading of the Achilles tendon is easily achieved by simply standing on the edge of a step or curb, suspending the heel. Just stand there, with tension on your tendons.

So does calf clenching work? I doubt it. There’s now failed replication of Rio et al.,14 plus other conflicting evidence,15 and so… meh.16

One could argue that isometric contractions are not a functional stimulus, and so they are unlikely to do much good, and the lack of consistent, persuasive results isn’t surprising.

Eccentric heel drops for Achilles tendinitis

Heels drops is a specific method of strengthening to treat Achilles tendinitis. Heel drops exercise the calf with “eccentric” contractions, which may stimulate greater adaptation of the tendon and constitute a treatment for Achilles tendinitis. In theory.

An eccentric contraction is just a contraction while lengthening, also sometimes called a braking contraction, and we use them all the time. This type of contraction is more efficient than concentric (harder work for less energy), and causes more soreness. The canonical example of an eccentric contraction is the biceps muscle while lowering a dumbbell: the muscle is lengthening, but clenching to control how fast it lengthens.

The eccentric contraction most relevant to Achilles tendinitis is the calf muscle. When you stand up on your toes, the calf contracts concentrically to lift you up. If you hold the position, that’s an isometric contraction. And then as you lower your heels down the calf contracts eccentrically. So a standard heel raise (with a bit of a pause at the top) uses all three.

The high “efficiency” of eccentric contractions makes them potentially useful for rehab.17 Eccentric exercise (EE) is often prescribed for tendinopathy, and especially Achilles tendinitis, because it seems to “improve symptoms,”18 and could even be a rare example of truly evidence-based rehab.19

On the other hand, nothing is ever that tidy in sports medicine. Or science. Or life.

Even if it is helping symptoms, recent evidence shows that EE may not actually be changing the tendon,20 which is probably what most people would hope and assume — a novel stimulus, with an interesting and useful tissue response, would be of great interest.

Today, many experts are just not impressed by eccentric exercise therapy, despite the sprinkling of positive studies: “There is no convincing clinical evidence to demonstrate that isolated eccentric loading exercise improves clinical outcomes more than other loading therapies.”21 But, years later, there is finally some convincing clinical evidence to demonstrate that eccentrics is not superior to other loading — a 2021 trial showed that they both deliver “equally good, lasting clinical results.”22 So it works well enough. It just doesn’t work better. It just works because all loading works, so why bother getting fancy and fiddly with it? People in that experiment were more satisfied doing regular exercises — probably because they’re less tedious!

Is there hope for eccentric training? Maybe “it depends” on unknown variables. But, if isolating eccentric contraction is actually useful in rehab, that is not clearly established yet,23 and I think the hope of that is fading steadily now.

Last word to Dr. Peter Malliaris:24

“Can authors please stop using this phrase: ‘the current gold standard for the treatment of Achilles tendinopathies is eccentric exercises.’ If ‘gold standard’ means the best available, the evidence does not support this.”

The Alfredson protocol for Achilles tendinitis: emphasizing the eccentric (for whatever it might be worth)

The eccentric exercise craze for Achilles tendinitis started with the “Alfredson protocol,” proposed way back in 1998 by Alfredson et al., a Swedish research group.25 A bunch of mediocre follow-up studies encouraged people who probably should have known better than to get “excited” about it. In 2012, the first longer-term study was finally published, which didn’t establish much except that many people quickly moved on from the Alfredson therapy to try other treatment methods — so it clearly wasn’t working any miracles — but they generally did well over time (though clearly not necessarily because of the Alfredson protocol).26

But enough of my nay-saying! I’ve done lots of this myself, despite my skepticism. And this is how it’s done…

Summarized, the Alfredson protocol is basically “lots of heel drops, with both bent and straight knee” where by “lots” I mean one hundred and eighty of them per day. That’s really a lot.

A heel drop is extremely simple: you just stand on the edge of something and lower ("drop") your heel down below the level of your toes a bit. The key to heel dropping the eccentric way is not to raise yourself back up with the leg you are treating. You get back to the starting position with your other leg.27

And what if your other leg has Achilles tendinitis? Then you can’t really do this, or at least not easily. It’s technically possible to get back to the start of the exercise without using either calf, with the right equipment… but it’s tricky.

And seriously, 180 drops per day? For many weeks? Ain’t nobody got time for that, and in fact the dosage is probably not all that important. A 2014 trial of 28 people (yes, tiny — almost all trials in this field are tiny) which found no significant difference between the Alfredson protocol’s high volume and a lower-volume version.28 So if you want to try this, here’s my recommendation, the modified Alfredson protocol. Ingredson protocol?

• Two exercises: one with straight knee, one with bent knee.
• Two sets per day.
• Fifteen repetitions of each exercise per set.
• For 8 weeks.
• The exercise itself:
  • Start on your tiptoes.
  • Lower your heel below your toes.
  • Step down.
  • Step back up with the other leg.

Achilles tendinitis pain relief options

“Masking symptoms,” especially with medications, is often maligned. But sometimes symptoms need masking! For instance, if you need a little pain relief during activity you cannot avoid (and many of us have activities we cannot avoid, like childcare and careers that naturally involve some tendon loading):

• Cautious, sparing use of Voltaren — a topical anti-inflammatory medication — might be effective for some people, and is much safer than oral anti-inflammatories. Or it might not work at all. The biochemistry of anti-inflammatory meds may just not be relevant to the biochemistry of irritated tendons.29
• Icing is mostly just for tactical pain relief, plus a small chance that icing can actually provide another source of useful stimulation-without-loading.

Just bear in mind that pain-relief and load management are natural enemies. Pain is generally a useful warning that we’re pushing tissue too hard. If you mute that signal, it’s much easier to accidentally leave the Goldilocks zone.

And also beware of overusing Voltaren or any other non-steroidal anti-inflammatory drug (like ibuprofen): there is some evidence that these drugs can actually interfere with healing, of both soft tissues like tendon30 and hard tissues too.31 Which really sucks.

Tendon rupture and surgical repair

Tendon rupture is mostly beyond the scope of this article for now, but a 2019 scientific review had such a surprising conclusion about this that it’s worth a mention. I think it has implications for all rehab, even of unruptured tendons.

Ochen et al. looked at ten trials and determined that surgery only modestly reduces the risk of re-rupture of the tendon, while introducing about a 2.5 times greater risk of complications (mostly infections).32 In other words, all other things being equal, the average patient with a ruptured Achilles tendon does approximately as well with or without surgery. For patients who did good rehab with an emphasis on early mobilizations, there was no difference in re-rupture risk at all. All the surgery did for those patients was give them a risk of complications that they wouldn’t have had otherwise.

The surprising part here is not only that it’s possible to heal from tendon ruptures without surgery, but that it’s possible to do it well — potentially just as well as with surgery, and certainly not much worse. How do ruptured tendons heal on their own without being surgically reattached? I can’t really explain it. Something is obviously wrong with my mental model, because if tendon rupture works the way I imagine it, then healing without surgical fixation of the tendon seems impossible. Let’s chalk it up to a terrific example of the healing powers of the human body. Animals have to be able to heal from tendon ruptures without surgery, and we can.

It’s also a good example of how many orthopedic surgeries are surprisingly useless, even the ones where the need for “repair” seems “obvious” — this is something research has been exposing regularly since the mid-2000s.33 See the next section for another good specific example.

This evidence strongly validates conventional rehab in general, and especially suggests that getting going with pain free range of motion exercises ASAP is particularly valuable — even with a ruptured tendon! And if it’s helpful for a ruptured tendon, it’s probably good for any case of tendinopathy. Use it or lose it!

Treating calcific Achilles tendinitis with surgery

Calcific tendinitis is an unusually painful kind of tendinitis — as I know all too well. I had it a few years ago, and I suspect it will hold the record for my most painful experience for a long time. 0/10, do not recommend.

The tendon gets a bit “crispy” with deposits of calcium — not actually crispy, but it’s a fun way to describe it.34 A common treatment approach in the last few decades has been to surgically “clean” the tendon (lavage).

But more and more common orthopaedic surgeries are being tested against shams and losing — as just mentioned above — and now you can add to the list.35 They studied shoulder tendinitis, but the results very likely apply to any calcific tendinitis. The details of their methods are a bit of a brain-teaser (they also mixed some steroids into the recipe), but the bottom line is that this study showed that lavage could not beat a sham.

That is, fake surgery for crispy tendons is probably the same as the real deal! So you probably don’t want that. The risks of surgery are never worth it if it they aren’t offset by clear benefits.

If we have learned anything from the last three decades of rehab research, it’s that we often can’t fix “obvious” problems by trying to remove the obvious part. The likely implication here is that calcification is just the tip of the pathological iceberg that makes the condition suck.

Regenerative medicine for Achilles tendinitis

There are some emerging high-tech treatments intended to stimulate/accelerate tendon tissue growth. These are exciting possibilities, but I think you should save your money for now.

This website has a salamander for a mascot/logo because that critter has genuinely amazing powers of regenerative healing. We know it’s possible because salamanders do it: the only macroscopic animal with that superpower.

But we certainly don’t have it yet. We’ll probably get some real regenerative medicine eventually, but it’s still early days. Meanwhile, there are several companies racing to market on this. Their value can only be based on hype, because none of them have been adequately tested yet. Tendoncel is the most prominent I know of, and by their own admission they are still testing their product.

There’s also platelet-rich plasma injection — basically, injecting a sauce of your own platelets — which is a poor man’s version of stem cell therapy, less new, and less promising. Despite widespread claims of efficacy, the evidence is extremely weak sauce. I cannot recommend PRP at this time. I review that topic in detail in a separate article: Does Platelet-Rich Plasma Injection Work? An interesting treatment idea for arthritis, tendinopathy, muscle strain and more.

So there’s just no basis for confidence about any regenerative therapy for tendons at this time. It’s implausible on its face, because there are extremely few precedents for clearly successful regenerative medicine in humans, and many conspicuous failures.

That doesn’t mean it won’t work, but it does mean that the bar for the evidence is very high, and even if we see evidence of efficacy soon, it will definitely still not be enough: it will have to be replicated independently.

So, as of 2022, we’re a ways off yet — probably years off.

Orthotics for Achilles tendinitis

Orthotics are generally over-rated, and the industry that supplies that is pretty rotten with nonsense.36 Orthotics are often recommended for conditions remote from the feet, allegedly because foot biomechanics are relevant to the function of practically everything else in the body. People love this idea, and it sells, but it has not stood up to scrutiny, and is one of the best examples of the failed paradigm of “structuralism” in rehab and pain medicine. Structuralism is the excessive focus on causes of pain like crookedness and biomechanical problems.37

Practically every imaginable condition below the knee can supposedly be treated by orthotics. Some of them are undoubtedly legit. Not Achilles tendinitis. An excellent 2015 study slammed the door shut on this topic, a rare case of a study that was good enough to actually produce a persuasive answer, instead of just more low quality evidence that has to be taken with a huge grain of salt.38

This was a controlled test of customized orthotics for Achilles tendinitis, compared to a sham of off-the-shelf orthotics. The design and methodology were solid: straightforward and with plenty of statistical power (140 subjects in two groups). They checked up on everyone at intervals for a year, and found … no difference at any point. Everyone improved somewhat, but the custom orthotics did not grant any advantage. The bottom line:

Customised foot orthoses… are no more effective than sham foot orthoses.

This is the kind of conclusion that orthotics makers really do not want anyone to know about. Achilles tendinitis is exactly the kind of condition that custom orthotics can supposedly work marvels with, and failing this test so completely is really damning for that industry. Unsurprisingly, the researchers have been harshly criticized, and they have responded to those criticisms at length — and I don’t think any of the criticisms hold up.

Do not spend your money on custom orthotics for Achilles tendinitis.

Topical glyceryl trinitrate (GTN) for Achilles tendinitis

This is about nitroglycerin as a medicinal ointment. And, yes, that nitroglycerin: the clear, pale-yellow fluid that can go kaboom in the right conditions. Nitro has a colourful history, from dynamite to treating cocaine side effects, angina, and (it’s most common modern usage) anal fissures. Most people don't even know that it has medical uses other than heart pain. By tradition, doctors call it glyceryl trinitrate, just avoid the awkward questions … but it is literally the same stuff.

Nitro itself isn’t the medicine: it is quickly converted by the body into nitrous oxide (NO), and that is the active ingredient. NO is a powerful vasolidator, so it plugs right into our infinite appetite for things that might be therapeutic because they increase circulation. But NO may also be anti-inflammatory, analgesic, and — most importantly — it might be a tendon builder, a stimulant to connective tissue synthesis. This idea was originally proposed in the late 90s, and has been floating around ever since, perpetually unconfirmed.

This is the GTN ointment that was used in the study. Availability of nitro ointments and patches is patchy around the world. For instance, “it was not possible to use altered or cut transdermal GTN patches for the purpose of this trial, in line with European Union regulations.” Most nitro ointments are for anal fissues, and have re-for-rectal names like Rectogesic, Repane, and (on-the-nose) Recto-Relief. (Get a load of the cheesy anal-pain graphics here! It also includes a fully illustrated guide to usage, and I do mean FULLY.) You can use the made-for-butts nitro products on your tendons. It is exactly the same stuff.

Nitroglycerin is one of the more obscure over-the-counter prescriptions in the rehab world, and the evidence has been thin and mixed.

A variety of reviews have come to a variety of conclusions. A 2019 review is a positive example.39 The authors endorse the stuff for tough cases, and I don’t disagree that it’s worth a shot, but their data hardly gets my motor running — it’s mixed and mostly mediocre. While the conclusion seems positive, but it’s not resting on much, and some other reviews have been negative. So how good can it be?

A 2024 trial is probably the best-ever test of GTN, and it was resoundingly negative: zero difference between people who used nitrogen daily for months, and people who used a sham.40 That was the first good quality RCT in twenty years — and the older one, which was really quite similar, reported good results.41 What gives? It may be as simple as a dosage difference.42 If the only two good trials were both negative, I would say “case probably closed.” But as it is, I think it would be a mistake for a careless skeptic to point to this paper and scoff at nitro for tendons. More study is actually needed.

Figure 3, Kirwan et al. 2024, British Journal of Sports Medicine

That is about as simple and clear as a graph of trial results can get! Even where the GTN and the placebo differ, the gap is much smaller than the error bars. Just absolutely no difference. But — and this is THE question about this study — would a higher dose of GTN have pushed that blue line higher than the pink? That’s not just speculation: that’s what Paoloni et al. reported in 2004.

Finally, this stuff absolute does give some people headaches, so there’s that. It’s not a terrible side effect, but it seems to be much more inevitable than any benefits. But it’s pretty cheap, safe, and not a crazy thing to try.

Massage for Achilles tendinitis

I am a former massage therapist, and a somewhat fancy one, well-trained by the standards of that profession — that’s how I originally got into writing about sports medicine, back in the early 2000s.43 Massage therapy can be a lovely sensory experience but is riddled with myths and misconceptions,44 and it is generally overrated as a therapy, especially for sports injuries (one of the areas of medicine it most aspires to participate in). This is a topic I have written about in extreme detail — an entire book, large parts of several other books, and dozens of chapters and articles.

From all that experience, I will extract a simple point here: massage is not very important to the Achilles tendinitis patient.

There’s really only way that it could be: if “tight” calf muscles contribute to excessive load on the Achilles tendon, and that in turn massage can “loosen” them.

Both ideas are weak hypotheses with numerous problems. Even if solid, actually using the tendon to walk, run, and jump would still probably still be responsible for the overwhelming majority of loading on the tendon. There isn’t a shred of direct or indirect evidence that any tendinopathy is a consequence of abnormally high muscle tone. Even people with serious neurological spasticity do not get extra tendinopathy!

A distant second place theory in this case: it’s not actually the tendon that is causing the pain: it’s muscle pain, either spreading from nearby muscle tissue into the tendon and/or muscle being mistaken for tendon, usually where it merges with it (the “musculotendinous junction”). That could be the case for some tendinitis, but it is not plausible for Achilles tendinitis.45

The role of the obscure plantaris muscle in Achilles tendinitis

There is one more odd, massage-adjacent idea about Achilles tendinitis to discuss: the fetishization of a trivial, almost vestigial muscle, entirely absent in many people. It’s a surprisingly popular idea that this teensy muscle is the real culprit, that a lot of Achilles tendinitis is actually plantaris tendinitis.

Not that it would matter much even if true.

Plantaris

The plantaris peaks out from behind the lateral head of gastrocnemius behind the knee, and is even skinnier than this drawing makes it look. But it does have a crazy long tendon that follows the Achilles through the ankle.

Plantaris is an odd, obscure, and really tiny muscle,46 … but it has one of the longest tendons in the body. The muscle crosses the knee diagonally from the outside above to the inside below, and then the barely-there tendon descends all the way down the back of the calf to attach to the inside of the heel — running alongside the Achilles tendon the whole way.

Maybe. Roughly. Like many small muscles, this one has seriously unpredictable anatomy, and it’s entirely missing in many of us, roughly 10%.47 A 2021 paper asks with its title, “Is the plantaris muscle the most undefined human skeletal muscle?”48 I think there are others that would give it a run for its money, but it is a weird one.

Plantaris can probably be considered vestigial. Technically, it does the same pulling job as some of the big calf muscles, but it’s usually too small — even its larger versions — to make any serious contribution.

Is some Achilles tendinitis actually plantaris tendinitis?

I think it’s extremely unlikely, and unimportant even if true, because it has no treatment implications. How would you use your leg differently to reduce load on the plantaris tendon? You can’t. Could you stimulate the plantaris specifically, with eccentric training? You could not. Its barely-there job overlaps too much with the rest of the calf — anything you do for plantaris is going to be the same as what you’d do for the Achilles tendon.

Would you massage the plantaris muscle to reduce the tone of the plantaris muscle? You could, but I don’t know why you’d bother. The back of the knee is a somewhat vulnerable spot, unpleasant and unsatisfying to massage; the plantaris belly is redundant with the heads of the gastrocnemius muscle anyway. And even if you could effectively rub just, it strikes me as nearly impossible that it would be clinically significant.

Even if plantaris tendinitis accounts for some significant percentage of “Achilles” tendinitis — highly doubtful — it’s a diagnostic distinction without a difference.

There’s not really much to Achilles tendinitis treatment

Someday I will expand this guide into a book, and go on and on and on for 50x as long, delving into all the weird little details (things like the role of plantaris are starting to really get into the weeds, but it’s the tip of the iceber).

But no matter how much more I write about it, the bottom line won’t actually differ much from what you’ve seen here. “Progressive loading” is mostly all there is to know. Shhhhh. Our little secret.

About Paul Ingraham

I am a science writer in Vancouver, Canada. I was a Registered Massage Therapist for a decade and the assistant editor of ScienceBasedMedicine.org for several years. I’ve had many injuries as a runner and ultimate player, and I’ve been a chronic pain patient myself since 2015. Full bio. See you on Facebook or Twitter., or subscribe:

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Notes

1. Habets B, van den Broek AG, Huisstede BMA, Backx FJG, van Cingel REH. Return to Sport in Athletes with Midportion Achilles Tendinopathy: A Qualitative Systematic Review Regarding Definitions and Criteria. Sports Med. 2018 Mar;48(3):705–723. PubMed 29249084 ❐ PainSci Bibliography 51928 ❐

   “We found that only one-third of the included studies used RTS as an outcome, with a RTS rate ranging between 10 and 86% after 12 weeks [citing Mafi and Roos]. These studies used different definitions (e.g. ‘return to previous activity level’ or ‘return to full activity’), which makes comparison of their RTS rates difficult. In many other AT studies, RTS is either not the main outcome of the study or is not evaluated at all. This results in a lack of clear definition of RTS and an absence of well-defined criteria for RTS.”

2. The risk factors are probably both biological and behavioural: some people are probably just more prone to overdoing it, which likely accounts for a significant percentage of the cases that go poorly.
3. Gajhede-Knudsen M, Ekstrand J, Magnusson H, Maffulli N. Recurrence of Achilles tendon injuries in elite male football players is more common after early return to play: an 11-year follow-up of the UEFA Champions League injury study. Br J Sports Med. 2013 Aug;47(12):763–8. PubMed 23770660 ❐
4. Heinemeier KM, Schjerling P, Heinemeier J, Magnusson SP, Kjaer M. Lack of tissue renewal in human adult Achilles tendon is revealed by nuclear bomb (14)C. FASEB J. 2013 May;27(5):2074–9. PubMed 23401563 ❐ PainSci Bibliography 53171 ❐
5. Heinemeier KM, Schjerling P, Øhlenschlæger TF, et al. Carbon-14 bomb pulse dating shows that tendinopathy is preceded by years of abnormally high collagen turnover. FASEB J. 2018 09;32(9):4763–4775. PubMed 29570396 ❐
6. We can put a man on the moon, but we can’t treat chronic pain. The science and treatment of pain and injury was neglected for decades while medicine had bigger fish to fry, and it remains a backwater to this day. The seemingly simpler “mechanical” problems of injury and rehab have proven to be surprisingly weird and messy. Oversimplification and quackery still dominate the field. For more information, see A Historical Perspective On Aches ‘n’ Pains: Why is healthcare for chronic pain and injury so bad?
7. Tweet, Sep 24, 2014, Greg Lehman (@GregLehman), physical therapist and chiropractor.
8. Soligard T, Schwellnus M, Alonso JM, et al. How much is too much? (Part 1) International Olympic Committee consensus statement on load in sport and risk of injury. Br J Sports Med. 2016 Sep;50(17):1030–41. PubMed 27535989 ❐

   This is the first of a pair of papers (with Schwellnus) about the risks of athletic training and competition intensity (load). Is load a risk for injury and illness? How much is too much? Is too little a problem? These papers were prepared by a panel of experts for the International Olympic Committee, and both them use many words to say the same things formally — but they are good points. Here they are in plain English:

   • There’s not enough research, surprise surprise, and what we do know is mostly from limited data about a few specific sports. But there’s enough to be confident that “load management” overall is definitely important.
   • Both illness and injury seem to have a similar relationship to load — lots of overlap.
   • Too much and not enough load probably increase the risk of both injury and illness. You want to be in the goldilocks zone! But the devil is in the details …
   • Not everyone is vulnerable to high load, and elite athletes are the most notable exception: they are relatively immune to the risks of overload, probably because of genetic gifts. Everyone else gets weeded out!
   • Big load changes — dialing intensity up or down too fast — are much bigger risks than absolute load. If you methodically work your way up to a high load, it may even be protective.
   • “Load” can also refer to non-sport stressors and “internal” loads, which are legion. Psychology, for instance, probably does matter: anything from daily hassles to major emotional challenges, as well as stresses related to sport itself.
9. Johannsen F, Jensen S, Wetke E. 10-year follow-up after standardised treatment for Achilles tendinopathy. BMJ Open Sport Exerc Med. 2018;4(1):e000415. PubMed 30305926 ❐ PainSci Bibliography 52260 ❐
10. Ingraham. The Art of Rest: The finer points of resting strategy when recovering from injury and chronic pain (hint: it’s a bit trickier than you might think). PainScience.com. 6886 words. Resting “properly” is trickier and a more critical part of injury rehabilitation than most people realize, and is often at odds with a culture tradition of aggressive therapeutic exercise (“no pain, no gain”). This article explores the rationale for resting, and tactical considerations like how to rest anatomy that you need to use for your job, and how to know how much rest is enough.
11. FDA Drug Safety Communication. “FDA warns about increased risk of ruptures or tears in the aorta blood vessel with fluoroquinolone antibiotics in certain patients.” Updated Dec 21, 2018. Accessed Feb 17, 2020.
12. Alves C, Mendes D, Marques FB. Fluoroquinolones and the risk of tendon injury: a systematic review and meta-analysis. Eur J Clin Pharmacol. 2019 Oct;75(10):1431–1443. PubMed 31270563 ❐
13. Rio E, van Ark M, Docking S, et al. Isometric Contractions Are More Analgesic Than Isotonic Contractions for Patellar Tendon Pain: An In-Season Randomized Clinical Trial. Clin J Sport Med. 2017 May;27(3):253–259. PubMed 27513733 ❐
14. Holden S, Lyng K, Graven-Nielsen T. The Acute Effect of Isometric Versus Isotonic Resistance Exercise in Patients With Patellar Tendinopathy—does contraction type matter? A randomised crossover trial. {Presented at the Scandinavian Sports Medicine Conference, Copenhagen, Denmark, 2019}. 2019. PainSci Bibliography 52445 ❐
15. O’Neill S, Radia J, Bird K, et al. Acute sensory and motor response to 45-s heavy isometric holds for the plantar flexors in patients with Achilles tendinopathy. Knee Surg Sports Traumatol Arthrosc. 2018 Jul. PubMed 29974171 ❐
16. Gravare Silbernagel K, Vicenzino BT, Rathleff MS, Thorborg K. Isometric exercise for acute pain relief: is it relevant in tendinopathy management? Br J Sports Med. 2019 May. PubMed 31076398 ❐ PainSci Bibliography 52418 ❐
17. Hessel et al.: “The high force and low energy cost of eccentric contractions makes them particularly well suited for athletic training and rehabilitation. Eccentric exercise is commonly prescribed for treatment of a variety of conditions including sarcopenia, osteoporosis, and tendinosis.”
18. Frizziero A, Vittadini F, Fusco A, Giombini A, Masiero S. Efficacy of eccentric exercise in lower limb tendinopathies in athletes. J Sports Med Phys Fitness. 2016 Nov;56(11):1352–1358. PubMed 26609968 ❐ “Eccentric exercise (EE) is considered a fundamental therapeutic resource, especially for the treatment of Achilles and patellar tendinopathies.”
19. Rees JD, Wolman RL, Wilson A. Eccentric exercises; why do they work, what are the problems and how can we improve them? Br J Sports Med. 2009 Apr;43(4):242–6. PubMed 18981040 ❐ “Eccentric exercises (EE) have proved successful in the management of chronic tendinopathy, particularly of the Achilles and patellar tendons, where they have been shown to be effective in controlled trials.”
20. Drew BT, Smith TO, Littlewood C, Sturrock B. Do structural changes (eg, collagen/matrix) explain the response to therapeutic exercises in tendinopathy: a systematic review. Br J Sports Med. 2014 Jun;48(12):966–72. PubMed 23118117 ❐ “The available literature does not support observable structural change as an explanation for the response of therapeutic exercise except for some support from heavy-slow resistance training.” It’s conceivable that moderate intensity eccentric contractions are just somewhat closer to the real goal of “heavy-slow resistance training” — a shortcut.
21. Couppé C, Svensson RB, Silbernagel KG, Langberg H, Magnusson SP. Eccentric or Concentric Exercises for the Treatment of Tendinopathies? J Orthop Sports Phys Ther. 2015 Nov;45(11):853–63. PubMed 26471850 ❐
22. Beyer R, Kongsgaard M, Hougs Kjær B, et al. Heavy Slow Resistance Versus Eccentric Training as Treatment for Achilles Tendinopathy: A Randomized Controlled Trial. Am J Sports Med. 2015 Jul;43(7):1704–11. PubMed 26018970 ❐
23. Murphy MC, Travers MJ, Chivers P, et al. Efficacy of heavy eccentric calf training for treating mid-portion Achilles tendinopathy: a systematic review and meta-analysis. Br J Sports Med. 2019 Sep;53(17):1070–1077. PubMed 30636702 ❐
24. Malliaras P, Barton CJ, Reeves ND, Langberg H. Achilles and patellar tendinopathy loading programmes : a systematic review comparing clinical outcomes and identifying potential mechanisms for effectiveness. Sports Med. 2013 Apr;43(4):267–86. PubMed 23494258 ❐
25. Alfredson H, Pietilä T, Jonsson P, Lorentzon R. Heavy-load eccentric calf muscle training for the treatment of chronic Achilles tendinosis. Am J Sports Med. 1998;26(3):360–6. PubMed 9617396 ❐
26. van der Plas A, de Jonge S, de Vos RJ, et al. A 5-year follow-up study of Alfredson's heel-drop exercise programme in chronic midportion Achilles tendinopathy. Br J Sports Med. 2012 Mar;46(3):214–8. PubMed 22075719 ❐ PainSci Bibliography 54410 ❐
27. The idea is to emphasize eccentric contraction, but normal heel raises include equal doses of concentric and eccentric contraction. What goes up must come down! So how do you separate them? You have to make a point of eliminating the concentric — which means that you just don’t do the “raise” part of heel raises. You stand on the edge, lower your heel, and then rather than lifting back up again, you just take the load off with your other leg, reset, and repeat. Just never raise with the calf you’re training. For whatever it’s worth.
28. Stevens M, Tan CW. Effectiveness of the Alfredson protocol compared with a lower repetition-volume protocol for midportion Achilles tendinopathy: a randomized controlled trial. J Orthop Sports Phys Ther. 2014 Feb;44(2):59–67. PubMed 24261927 ❐
29. Heinemeier KM, Øhlenschlæger TF, Mikkelsen UR, et al. Effects of anti-inflammatory (NSAID) treatment on human tendinopathic tissue. J Appl Physiol (1985). 2017 Nov;123(5):1397–1405. PubMed 28860166 ❐ This study reported that “tendinopathic cells are not responsive to ibuprofen.”
30. Bittermann A, Gao S, Rezvani S, et al. Oral Ibuprofen Interferes with Cellular Healing Responses in a Murine Model of Achilles Tendinopathy. J Musculoskelet Disord Treat. 2018;4(2). PubMed 30687812 ❐ PainSci Bibliography 52446 ❐ “We conclude that the use of Ibuprofen for pain relief during inflammatory phases of tendinopathy, might interfere with the normal processes of extracellular matrix remodeling and cellular control of expression of inflammatory and wound healing genes.”
31. Wheatley BM, Nappo KE, Christensen DL, et al. Effect of NSAIDs on Bone Healing Rates: A Meta-analysis. J Am Acad Orthop Surg. 2019 Apr;27(7):e330–e336. PubMed 30260913 ❐

    This is a meta-analysis of 16 trials, showing that common over-the-counter pain-killers interfere with bone healing. Chronic overuse roughly doubles the risk that a fracture will heal slowly or not at all (“non-union,” a very serious complication).

    The effect was not evident in children or in lower doses or temporary usage — this bad news applies only to adults taking too much of the stuff for too long. Unfortunately, a lot of people do that! The pain-killers in question are the non-steroidal anti-inflammatory drugs or NSAIDs like aspirin, ibuprofen, and naproxen — already notorious for several other significant side effects, and yet still widely overused.

32. Ochen Y, Beks RB, van Heijl M, et al. Operative treatment versus nonoperative treatment of Achilles tendon ruptures: systematic review and meta-analysis. BMJ. 2019 Jan;364:k5120. PubMed 30617123 ❐ PainSci Bibliography 52396 ❐
33. Louw A, Diener I, Fernández-de-Las-Peñas C, Puentedura EJ. Sham Surgery in Orthopedics: A Systematic Review of the Literature. Pain Med. 2016 Jul. PubMed 27402957 ❐ PainSci Bibliography 53458 ❐

    A review of a half dozen high quality tests of four popular orthopedic (“carpentry”) surgeries, all showing a lack of efficacy compared to placebos. This review is an excellent academic citation to support the claim that sham surgery has shown to be just as effective as actual surgery in reducing pain and disability. It’s also an eyebrow-raiser that Louw et al. could find only six good (controlled) trials of orthopedic surgeries, and all of them were bad news.

    (See more detailed commentary on this paper.)

34. “Crispy” is evocative hyperbole reflecting popular perception of calcification. The reality is that tendinous calcifications tend to be more wispy than crispy: diffuse accumulations of calcium deposits throughout the tissue, not actually even a solid, much closer to damp snowflakes than dry cornflakes. They tend to look much more bone-like on an x-ray than they actually are, because calcium reflects x-rays quite well.
35. Moosmayer S, Ekeberg OM, Hallgren HB, et al. Ultrasound guided lavage with corticosteroid injection versus sham lavage with and without corticosteroid injection for calcific tendinopathy of shoulder: randomised double blinded multi-arm study. BMJ. 2023 Oct;383:e076447. PubMed 37821122 ❐ PainSci Bibliography 51500 ❐
36. Ingraham. Are Orthotics Worth It? A consumer’s guide to the science and controversies of custom orthotics, orthopedic shoes, and other allegedly corrective foot devices. PainScience.com. 5581 words.
37. “Structuralism” is the excessive focus on crookedness and “mechanical” problems as causes of pain. It has been the dominant way of thinking about how pain works for decades, and yet it is a source of much bogus diagnosis. Structuralism has been criticized by several experts, and many studies confirmed there are no clear connections between biomechanical problems and pain. Many fit, symmetrical people have severe pain problems! And many crooked people have little pain. Certainly there are some structural factors in pain, but they are generally much less important than messy physiology, neurology, psychology. Structuralism remains dominant because it offers comforting, marketable simplicity. For instance, “alignment” is the dubious goal of many major therapy methods, especially chiropractic adjustment and Rolfing. See Your Back Is Not Out of Alignment: Debunking the obsession with alignment, posture, and other biomechanical bogeymen as major causes of pain.
38. Munteanu SE, Scott LA, Bonanno DR, et al. Effectiveness of customised foot orthoses for Achilles tendinopathy: a randomised controlled trial. Br J Sports Med. 2015 Aug;49(15):989–94. PubMed 25246441 ❐
39. Challoumas D, Kirwan PD, Borysov D, et al. Topical glyceryl trinitrate for the treatment of tendinopathies: a systematic review. Br J Sports Med. 2019 Feb;53(4):251–262. PubMed 30301735 ❐ PainSci Bibliography 51890 ❐
40. Kirwan PD, Duffy T, French HP. Topical glyceryl trinitrate (GTN) and eccentric exercises in the treatment of mid-portion achilles tendinopathy (the NEAT trial): a randomised double-blind placebo-controlled trial. Br J Sports Med. 2024 Sep;58(18):1035–1043. PubMed 39013615 ❐ PainSci Bibliography 49739 ❐

    Kirwan et al. tested topical nitro in a few dozen Irish folks at a Dublin hospital. They compared nitro to an “aqueous cream, which contained no ingredients that would aid in tendon recovery.” (And yet I can so easily imagine some crank arguing that tendons need to be hydrated. Easily.)

    Everyone also did the same exercise program for six months: the Alfredson protocol (predictably), a bunch of calf exercise made fiddly by doing them the eccentric way (loaded elongation). “It is known” that the Alfredson protocol is no better than simpler weighlifting. The authors reference that evidence from 2015, explaining that it was “published after this trial was designed” … so this trial took at least a decade to pull off? Wowsers.

    All that exercise, plus time, means that everyone was likely to get better, and they did. But did nitro-smeared heels heal faster?

    The answer was … no difference. An utterly negative result on its face. Nitro conveyed no advantage whatsoever. It did convey some headaches though — a well-known side effect.

    Figure 3, Kirwan et al. 2024, British Journal of Sports Medicine

    That is about as simple and clear as a graph of trial results can get! Even where the GTN and the placebo differ, the gap is much smaller than the error bars. Just absolutely no difference.

41. Paoloni JA, Appleyard RC, Nelson J, Murrell GAC. Topical glyceryl trinitrate treatment of chronic noninsertional achilles tendinopathy. A randomized, double-blind, placebo-controlled trial. J Bone Joint Surg Am. 2004 May;86(5):916–22. PubMed 15118032 ❐

42. Kirwan et al. speculate that it could be chalked up to their different outcome measures and/or dosage.

    Paoloni et al. used more nitro, from a patch, and reported both more benefit and more harm: more tendinitis relief, more headache grief! This could be a really tidy example of how a relatively small detail might make all the difference, and explain how two good quality trials can produce completely different results.

    And so, surprisingly, the conclusion of the newer study is less negative than its results. On the one hand:

    Although three systematic reviews have concluded that GTN is potentially beneficial in treating tendinopathy, our results do not support the use of topical GTN ointment in treating Achilles tendinopathy.

    No, indeed, they do not. They also know that ointment “has been shown to be as effective as patches,” citing a study of anal fissures. But butts probably don’t heal the same as heels, so that’s hardly conclusive.

    And so, on the other hand, maybe this new trial was negative just because they needed more nitro:

    In light of our incomplete understanding of tendon pathophysiology, the study of GTN is warranted, as basic science, animal and human studies have confirmed NO as an important chemical messenger in tendon pathology and repair.

43. I was a Registered Massage Therapist with a busy practice in Vancouver, Canada, from 2000–2010, RIP. After that, science journalism and this website took over my career and they remain my sole focus today. See my bio.

44. The major myths about massage therapy are that it…

    • fixes “tightness”
    • increases circulation. and detoxifies and therefore patients need to drink extra water to “flush” liberated toxins
    • reduces soreness after exercise.
    • reduces inflammation.
    • stimulates endorphins (natural opioid) and reduces cortisol (stress hormone)

    Importantly, both of the Big Two popular modalities in massage — fascia and trigger point therapy — are scientifically half-baked at best. The complete list of dubious ideas in massage therapy is much larger. See my general massage science article. Despite all this, massage is still awesome! See also Reassurance for Massage Therapists: How ethical, progressive, science-respecting massage therapists can thrive in a profession badly polluted with nonsense.

45. There is a poorly understood relationship and gray zone between tendon overload and muscle fatigue. In some tendinitis, like tennis elbow, where the muscle "mixes" more with the tendon, the discomfort caused by irritated muscle and irritated tendon may be harder to separate, and massage often seems more relevant. There’s a span of several centimetres in the arm where there is an anatomical blend of both tendon and muscle. But in the calf, there is no such zone of muscle/tendon ambiguity, and the irritated Achilles tendon is quite distinct from most of calf musculature.
46. It’s so slight that students mistake it for a nerve during cadaver dissections, giving it the nickname “freshman’s nerve” or “fool’s nerve.”
47. Simpson SL, Hertzog MS, Barja RH. The plantaris tendon graft: an ultrasound study. J Hand Surg Am. 1991 Jul;16(4):708–11. PubMed 1880370 ❐ )
48. Kurtys K, Gonera B, Olewnik Ł, et al. Is the plantaris muscle the most undefined human skeletal muscle? Anat Sci Int. 2021 Jun;96(3):471–477. PubMed 33159667 ❐ PainSci Bibliography 52096 ❐