Achilles tendonitis: the heel cord that hates mornings
Last updated September 3, 2026.
Achilles tendonitis (properly tendinopathy) is an overload injury of the body's largest tendon, the heel cord connecting calf to heel. Its calling cards: stiffness and pain at the back of the heel on the first morning steps, and a flare the day after too much running. It is common in runners and middle-aged weekend athletes, and it has one of the best-researched exercise treatments in sports medicine.
What does it feel like?
Morning stiffness at the back of the heel or lower calf that takes minutes to loosen, pain at the start of activity that eases as you warm up, and the next-day payback after you overdo it. The tendon may be thickened and tender to squeeze. The two types behave differently: mid-portion (the common one, 2-6cm above the heel) tolerates stretching and loading well; insertional (right at the heel bone) is aggravated by stretching into deep heel-drops and needs a modified program.
Why does it happen?
Load outrunning capacity: a training spike (the doubled mileage, the sudden hill phase, the new court sport), tight or weak calves, stiff ankles, worn shoes, and the age-related dip in tendon repair that makes 35-55 the peak band. Fluoroquinolone antibiotics (ciprofloxacin family) are a specific tendon hazard worth knowing. The sedentary version exists too: years of low load reduce capacity until ordinary activity overloads it.
What actually heals it?
- Progressive loading: the famous eccentric heel-drop program (slow lowers off a step) for mid-portion cases, or heavy slow calf raises, built over 12 weeks: this is the best-evidenced treatment in the whole of tendon medicine.
- Insertional version: heel raises only to floor level (no drops below the step), avoiding deep stretching and hills early on; a heel lift reduces compression at the sore point.
- Isometrics for pain: 45-second calf-hold contractions give hours of pain relief and keep you training.
- Modify, do not stop: cut running volume and hills to the tolerable level, swap some sessions for cycling or swimming, and keep the calf working.
- What to avoid: repeated steroid injections (they weaken this tendon specifically and raise rupture risk) and aggressive early stretching for the insertional type.
When is it an emergency?
Achilles tendinopathy is chronic; a rupture is urgent: a sudden snap or kick sensation at the heel with immediate inability to stand on tiptoe or push off walking needs same-day assessment (the squeeze test and early treatment decisions matter within days). A hot, red, swollen tendon area with fever needs same-day review for infection. And tendon pain starting during or soon after a fluoroquinolone antibiotic course deserves a prompt call about switching the drug. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
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Common questions
Can I keep running with Achilles tendonitis?
Usually yes, with the dose reduced: the evidence and clinical consensus favor modified running over complete rest, because tendons heal under load and detrain under rest. The working rules: cut volume and drop hills and speedwork, keep runs flat and easy, stay inside mild-discomfort-that-settles-by-next-morning, and do the loading exercises daily. The exception is pain that forces a limp or worsens step by step: that tendon needs a genuine break and often a boot for a short spell.
What are heel drops and do they really work?
The eccentric heel-drop protocol has the strongest evidence of any tendon treatment: standing on a step on the balls of both feet, rise up with both, then lower slowly (3-4 seconds) on the sore leg, heel below the step; classically 3 sets of 15, twice daily, progressed with added weight over 12 weeks. It hurts a bit, and that is expected and acceptable. Modern versions load both directions (heavy slow raises and lowers). The insertional variant skips the below-step part, because deep dorsiflexion compresses the tendon at the heel bone.
How long does it take to heal?
Budget three to six months: meaningful improvement typically arrives by 6-12 weeks of daily loading, but tendon remodeling is slow and the full job (thickening gone, mornings normal, full training resumed) often takes the longer figure. Insertional cases tend to run slower than mid-portion. The program works best done daily and continued past the first relief; most failures of the famous protocol are people who did it for three weeks, felt 70% better, and stopped.
Is a steroid injection an option?
Around the Achilles, the answer is unusually clear: no, unless circumstances are exceptional. Steroid injections near weight-bearing tendons, the Achilles above all, carry a documented rupture risk, and the tendon has a watershed blood supply that heals poorly once compromised. It is the one tendon where the usual injection debate barely exists. Pain control comes from isometrics, load management, and time; stubborn cases get shockwave therapy or, for true insertional failures, surgery, before anyone reaches for a needle.
I am on ciprofloxacin and my Achilles hurts. Related?
Possibly, and act on it today: fluoroquinolone antibiotics (ciprofloxacin, levofloxacin) carry a specific tendon-toxicity warning, with the Achilles the usual victim, sometimes within days of starting, and rupture risk is real, especially over 60 or with steroid use. The correct move: stop impact exercise immediately and contact the prescriber the same day about an alternative antibiotic; do not just stop a needed antibiotic without a replacement plan, but do not run on it either.
What is the rupture everyone warns about?
An Achilles rupture is the tendon snapping, typically during a sudden push-off or jump, described as a kick or a loud snap at the heel, followed by immediate inability to stand on tiptoe or push off the foot walking, sometimes with a feelable gap. It is a same-day assessment: early decisions (surgical repair versus a functional boot protocol, both with good outcomes) are time-sensitive over the first days. The squeeze test (calf squeezed while kneeling should make the foot point) is the classic check. Chronic tendinopathy raises rupture risk modestly; the warning signs before one are usually absent, which is why the snap itself is the alarm.