The pattern is unmistakable once you know it. The first few steps out of bed are the worst of the day. It loosens after ten minutes of walking. You run, and it feels almost fine. The next morning it is worse than before.
That is Achilles tendinopathy, and almost everything people instinctively do about it makes it last longer.
It is not tendonitis
The old name implied inflammation, and inflammation implies rest and anti-inflammatories. When these tendons are examined, there is very little inflammation to find.
What there is instead is a tendon that has been asked to do more than it could tolerate. The collagen fibres lose their neat parallel arrangement, the tendon thickens, new blood vessels and nerve endings grow into it, and the whole structure becomes less able to store and return energy. That is a capacity problem, not an inflammation problem.
The distinction is not academic. Inflammation is treated by calming things down. Reduced capacity is treated by building capacity back up. Those are opposite instructions, and following the wrong one is why so many Achilles problems drag on for a year.
Which part hurts matters a great deal
There are two versions, and they need different management. Press along the tendon and find where it is tender.
| Midportion | Insertional | |
|---|---|---|
| Where | 2 to 6 cm above the heel bone | Right at the back of the heel bone |
| Who | Runners, sudden training increases | Often less active people, sometimes with a bony spur |
| Stretching | Usually tolerated | Frequently makes it worse |
| Heel drops off a step | Helpful | Often provocative early on |
| Shoes | Less critical | A slight heel raise usually helps |
The insertional version is the one people get wrong. Dropping the heel below a step and stretching hard into dorsiflexion compresses the tendon against the heel bone, and compression is what an insertional tendon tolerates worst. If your pain is right at the bone and stretching makes it angrier, that is the reason.
Does this sound like yours?
- Stiff and sore for the first steps in the morning, easing within ten minutes
- Warms up during activity, then hurts more that evening or the next day
- Tender to squeeze the tendon between finger and thumb
- Sometimes a visible thickening or a lump partway up
- Worse after a jump in training, a new pair of shoes, or a change of surface
- Occasionally a creaking sensation early on
That morning stiffness is the single most useful diagnostic feature, and it is also the best way to monitor progress. If the first steps are getting easier week by week, the plan is working, whatever the tendon feels like mid-run.
Why it started
Tendons fail when load outruns capacity. Something changed:
- A training spike. More distance, more speed, more hills, or all three at once
- New footwear, particularly a drop from a cushioned heel to a flatter shoe
- A return after time off, going back to the old volume rather than building to it
- Calf weakness, so the tendon absorbs load the muscle should have taken
- Age, since tendons become less elastic from the forties onward
- Occasionally certain antibiotics, which is worth mentioning to your doctor
What actually helps
Do not stop moving. Complete rest reduces pain and reduces capacity further, so returning to activity loads a weaker tendon than the one that failed. Reduce the aggravating load rather than eliminating everything.
Load it, heavily and slowly. This is the treatment, and the evidence behind it is strong. Calf raises performed slowly, three seconds up and three seconds down, progressing to single leg and then to added weight. For midportion problems, progress to lowering the heel below the edge of a step. For insertional problems, keep the heel on flat ground until it settles.
Both knee positions. A straight knee loads the gastrocnemius, a bent knee loads the soleus underneath it. The soleus takes more load during running than most people realise, and it is routinely undertrained.
Accept some discomfort. Pain up to about four or five out of ten during the exercise is acceptable if it settles within 24 hours and the morning stiffness is not worse. That rule is what lets you train rather than tiptoe.
Stretch with judgement. A gentle calf stretch helps midportion problems. For insertional pain, leave it alone early on.
Give it three months. Tendons remodel slowly. Twelve weeks of consistent loading is a realistic timeline, and knowing that at the start prevents people abandoning at week four.
Things that are worth less than they sound
Anti-inflammatories treat something that is largely not there. Useful for a few days of severe pain, irrelevant to the underlying problem.
Injections into the tendon are avoided by most clinicians. Corticosteroid weakens tendon tissue and there are reports of rupture afterwards.
Orthotics and heel raises help insertional pain in the short term by reducing compression. They are a way to make loading possible, not a treatment on their own.
Shockwave therapy has moderate evidence and works alongside a loading programme, not instead of one.
What else it might be
- Plantaris irritation, felt on the inner side of the tendon, covered by the same approach
- Retrocalcaneal bursitis, tender in front of the tendon rather than on it
- Sever's disease in growing children, at the heel growth plate
- Heel pain underneath the foot, which is a different problem entirely and covered in our guide to plantar fasciitis
Get it assessed if
You felt a sudden snap or a blow to the back of the ankle and struggle to push off, which needs same-day medical assessment for a rupture. Also if the tendon is hot and swollen, if pain is severe at rest, if you have been loading consistently for three months with no change in the morning stiffness, or if you are taking a fluoroquinolone antibiotic and the tendon becomes sore.
Otherwise this responds well, and predictably, once the loading is right and the dose is honest. The two ways it goes wrong are stopping when it starts feeling better, and pushing harder because progress felt slow.