Achilles Tendinopathy

What it is

Achilles tendinopathy is pain, with swelling and limited function, in the thick tendon that joins the calf muscles to the heel. In the midportion type the pain sits 2 to 6 centimeters above where the tendon meets the heel bone. It typically shows up at the start of exercise and after it, and as the problem progresses it shows up during exercise too. A 2023 review reports that runners often feel it at the start and end of a session with less in between, and that morning stiffness tracks severity¹.

The second type is insertional, where the tendon attaches to the heel bone. In 3,379 recreational runners followed for about 20 weeks, a pain map classed most of the new cases as midportion, about a quarter as insertional and the rest as a combined type. Risk factors varied between the types but not by a clinically relevant amount².

Who gets it

A bout in the past 12 months is the strongest signal. In the same 3,379 runners, new Achilles tendinopathy was more common in men than in women, and tendinopathy in the previous 12 months made a new bout about six times as likely². A returning twinge in a tendon that hurt within the past year deserves an early response, not a wait-and-see.

A 2019 systematic review of ten cohort studies, all at high risk of bias, found limited evidence for nine risk factors, including a previous lower limb tendinopathy or fracture, ofloxacin (a quinolone antibiotic) and lower calf muscle strength pushing the foot down. Twenty-six other factors were not associated, including being overweight and static foot posture³. If you have recently taken an antibiotic of that class, tell your clinician.

What treats it

Loading exercise comes first. The 2024 US physical therapy guideline for midportion Achilles tendinopathy makes tendon loading exercise, with loads as high as tolerated, its first-line recommendation for people whose tendon is not presumed fragile, and advises doing it at least three times a week. It defines loading broadly, as eccentric, concentric, isometric, isotonic or plyometric work, and says clinicians are not limited to eccentric exercise because several loading types appear effective. In the studies it reviewed, benefit appeared as soon as 2 weeks, and care lasted from 6 weeks to 6 months⁴.

Nothing added to exercise has been shown to beat it. A 2023 network meta-analysis of 68 randomized trials across three tendinopathies rated every significant comparison low or very low in strength of evidence, found no convincing evidence that any added treatment, alone or alongside exercise, beats exercise alone, and recommended exercise on its own as first-line treatment for Achilles and patellar tendinopathy for at least 3 months before an add-on is considered⁵. The 2024 guideline makes no recommendation for orthoses, advises against low-level laser therapy, and advises against therapeutic ultrasound on its own⁴.

Plan in months, with a clinician setting the dose. The guideline describes progressive programs that take your total daily loading into account and allow more loading as the tendon's irritability changes⁴.

Running with it

Keep running if you can, at a lower dose. The guideline advises that complete rest is not indicated and that you continue your activities within your pain tolerance, and it lists pain monitoring as a self-management skill. A 2007 trial of 38 patients found that continuing running and jumping under a pain-monitoring model during a loading program gave no worse outcome than stopping for six weeks⁴⁶. In practice:

• Run at a level the tendon tolerates. A physical therapist's rule for returning runners: pain stays at 3 out of 10 or lower (4 at most) while you run and is stable or improving over the weeks, you stop the run if it climbs above that, and the tendon is back to its usual level within 24 hours of finishing. A limp, or any change in how you move, is a stop. Your clinician may set a different limit. The guide on return to running covers the order of return.
• Replace the running you cut with aerobic work that adds no lower-body impact, at an easy conversational effort, which is zone 2 in a five-zone model.
• Bring hills and fast running back last, one at a time, once easy running is pain-free.
• Keep the calf loading going after the pain settles by folding it into your regular strength work (see the guide on strength training for runners).

When to see a professional

A sudden, sharp pop or snap at the back of the ankle with a loss of push-off power can be a rupture and needs urgent assessment.

See a sports-medicine professional if Achilles pain lasts beyond a couple of weeks, is not improving or keeps returning when you build up. They confirm the diagnosis and set the loading program. Imaging is not needed to make the diagnosis, and the guideline reserves it for when the diagnosis is uncertain, recovery is delayed, symptoms worsen during care or a procedure is being considered⁴.