This tendon usually fails for reasons that are not in the tendon.

ACHILLES TENDINOPATHY

The Achilles is the strongest tendon in the body. When it degenerates, the explanation is almost never confined to the tendon — and this is the structure where that stops being a philosophical position and becomes a list of measurable things.

Midportion and insertional are different problems

Midportion tendinopathy sits two to six centimeters above the heel bone, in a watershed zone where blood supply is poorest. Insertional tendinopathy sits where the tendon attaches to the calcaneus, often with a bone spur, a retrocalcaneal bursa involved, and sometimes calcification within the tendon itself.

They respond differently to everything. Midportion responds well to eccentric loading; insertional often gets worse with the same exercise performed off a step, because dorsiflexion compresses the insertion against the bone. Getting this wrong is one of the most common reasons an Achilles rehabilitation program fails, and it is the first thing established here.

What is actually wrong with the tissue

Chronic Achilles pain is degenerative rather than inflammatory. The tendon shows collagen disarray, increased ground substance, and neovascularization — new vessels growing in from the anterior fat pad, accompanied by nerve fibers. Those accompanying nerves are a plausible source of the pain, which is why the tendon can hurt considerably while looking only moderately abnormal on imaging. The same mismatch, and why the word tendonitis keeps producing the wrong treatment, is on the tendinopathy page.

The reasons it fails are mostly not mechanical

Here is the number that reorganizes this whole page. A systematic review and meta-analysis pooling 31 studies found tendinopathy substantially more common in people with diabetes — an odds ratio of 3.67 (95% CI 2.71 to 4.97) across 17 studies. The relationship ran in both directions: diabetes was also more common in people with tendinopathy. People with both had carried diabetes about 5.26 years longer than people with diabetes and no tendinopathy, and their tendons were measurably thicker than controls.

That is a dose relationship with duration of exposure, in a structure most people think of as purely mechanical. Glycation cross-links collagen, stiffening the tendon and reducing how much strain it can absorb before it fails. Chronic metabolic inflammation holds the tissue in a degradative rather than a rebuilding state. And the Achilles, with the poorest perfusion of any tendon we treat, has the least margin to absorb either.

Then there is the exposure patients are rarely warned about. A systematic review found fluoroquinolone antibiotics associated with tendon injury and rupture, and the association is strongest at the Achilles. If this began within months of a course of one, that belongs in the history and it changes how cautiously we load you.

And the ordinary human driver, which is not in any paper. You cannot rest a leg. An elbow can be left alone; a tendon you stand on all day never gets the consolidation period the tissue is asking for.

So the first work here is not the injection. It is establishing what the tendon is being asked to repair in — the metabolic panel, the medication history, the sleep and the nicotine exposure. What gets measured, and why it comes before anything else, is on the metabolic health page.

Load is the treatment, and we say that first on purpose

A level-1 network meta-analysis of nonsurgical treatment for midportion Achilles tendinopathy pooled 22 randomized trials and 978 patients. Over the longer term, the wait-and-see approach performed markedly worse than eccentric exercise (standardized mean difference −1.51, 95% CI −2.02 to −1.01). The same analysis found that the additional treatments worth considering were ones added to a loading program rather than substituted for it.

That is the shape of the evidence, and it is why loading is not the thing we suggest while you wait for the real treatment. It is the real treatment. A catalyst is a step inside it.

One qualifier we will state rather than bury: that analysis ranked a high-volume injection containing corticosteroid among the useful additions. We do not make that trade at this tendon, and the reason is in the caution section below. Shockwave therapy is a reasonable further option with its own evidence base.

Where a catalyst fits, and where we will not put one

The rationale is the same as any stalled tendon: deliver a concentrated repair signal into a hypovascular degenerate zone, then organize the result with load. The multispecialty regenerative-medicine guidelines appraise tendon targets among their questions, and the sequencing they describe is the one used here — diagnostic work-up first, rehabilitation alongside, biologic after.

In practice that means a candidate is someone with a degenerate tendon who has completed a correct twelve-week program at the correct location and genuinely plateaued. Insertional disease, which responds less well to loading alone, is where the case for adding something is strongest.

What we will not do: inject a large volume inside the tendon substance, treat a partial tear as a tendinopathy, or place a catalyst into a body that has not had the terrain work started. Injection here is peritendinous and ultrasound-guided, because a small target sitting against a load-bearing structure is not somewhere to place a needle by feel.

Ruling out what it is not

• Partial tear — a distinct event, a palpable gap, or a sudden change in a chronically sore tendon, which changes management entirely.
• Retrocalcaneal bursitis — pain in front of the tendon rather than within it.
• Posterior ankle impingement — pain on forced plantarflexion, common in dancers.
• Inflammatory enthesitis — a seronegative spondyloarthropathy can present as Achilles pain, and it needs rheumatology rather than an injection.

How it is treated here

• Weeks 0 to 2. Protected weight-bearing, sometimes a heel lift to offload. Isometric calf holds for pain relief.
• Weeks 2 to 6. Eccentric or heavy slow resistance calf work — off a step for midportion disease, flat-footed only for insertional.
• Weeks 6 to 12. Progressive loading toward the demand you actually have, including speed if you run.
• Months 3 to 9. Continued loading. Achilles remodeling is slower than any other tendon on this site, and returning to impact early is how people relapse.

Why this tendon deserves more caution than most

The Achilles carries loads several times body weight with every step and has no redundancy. There is no second structure that quietly takes over if it fails. That single fact governs how it is treated here: no corticosteroid in or around it without a compelling reason, no large intratendinous volumes, and no rushing the return to impact because someone feels better at six weeks.

Feeling better is not the same as being ready. Tendon pain improves well before tendon capacity does, and that gap — comfortable but not yet strong — is exactly where re-injury happens. It is why we keep loading people for months after the symptoms have quietened, and why a program that stops when the pain stops tends to produce a second episode inside the year.

The two questions that decide this

Everything above reduces to two questions, asked in this order.

• Which Achilles problem is it? Midportion and insertional are not variants of one condition. Midportion responds well to loading, which is why an injection there is a second move rather than a first. Insertional responds less well, which is where the case for adding something is stronger. We will tell you which one you have before we tell you what we use.
• Has the loading program actually been done, and was it the right one? Not attempted. Not described in a leaflet. Done, for twelve weeks, at the correct location for the correct problem. The number of people sent here for an injection who have never had a correct loading program is the single most common finding in this clinic.

Answer both and the decision usually makes itself. A degenerate midportion tendon in someone who has genuinely completed a proper program and plateaued is a reasonable candidate. An insertional problem with the same history is a stronger one. A partial tear, a palpable gap or a sudden change in a chronically sore tendon is not a candidate at all — that is a structural event and it is managed as one.

When it still does not settle

Check the diagnosis first, particularly for a missed partial tear or an inflammatory cause. Then check whether the loading was correct for the location, because a midportion program applied to an insertional problem fails reliably. Then check what has changed in the terrain since the first visit. Only after those three does a second injection or a surgical opinion belong in the conversation.

What people ask about an Achilles that will not settle

Is an injection the answer for Achilles tendinopathy?

Not as a first move for midportion disease, because loading is the treatment with the strongest support here and a catalyst works on a repair that has stalled rather than one that has never been properly loaded. Where a biologic does fit in the sequence is set out on the timing page.

Should I have a cortisone injection instead?

Around the Achilles, generally no — the association with rupture makes it a poor trade in a structure with no redundancy, whatever the short-term relief. The full comparison is on the cortisone page.

I have diabetes. Does that change my chances?

It changes the odds of having this at all — tendinopathy was roughly three and a half times as common in people with diabetes in the pooled data, and longer duration of diabetes carried more of it. It is also the most modifiable thing on your list, which is why we start with the bloodwork.

I took an antibiotic and this started. Is that related?

Possibly, if it was a fluoroquinolone, and it is worth telling us because it changes how cautiously we load you and how long we expect remodeling to take. How that feeds into the decision is on the candidacy page.

How long before I can run?

Months rather than weeks, and the gate is load tolerance rather than the calendar, because capacity returns well after comfort does. The honest version of the schedule is on the recovery timeline.

Related reading

• Why the word tendonitis produces the wrong treatment
• Why we ask for your bloodwork
• Plantar fasciitis
• The ankle sprain that never came right
• What recovery here looks like
• Risks and side effects