The Achilles is the strongest tendon in the body and takes several times body weight with every running stride. It responds well to load applied gradually, and badly to load applied suddenly.
What usually causes it
- A sudden increase in running volume, speed or hill work.
- Tight or weak calves, so the tendon absorbs what the muscle should have.
- A change of footwear, particularly dropping to a lower heel.
- Restricted ankle movement, changing how the foot loads.
An important warning
A sudden, severe pain like being kicked or shot in the back of the ankle, usually with an audible snap and an inability to push off, may be an Achilles rupture. That is an emergency — go to A&E the same day. It is frequently mistaken for a bad calf strain, and delay affects the outcome.
Ordinary tendinopathy comes on gradually over weeks. Rupture happens in an instant.
What treatment involves
Soft tissue work through the calf complex to reduce the pull on the tendon, work on the tendon itself, and restoring ankle mobility.
Then loading. As with any tendon, the treatment that changes the tissue is progressive strengthening — calf raises loaded and built up steadily over months. Hands-on work makes that possible and more comfortable; it does not replace it.
How long
Months, not weeks, and improvement is gradual rather than sudden. Tendons are slow. The people who recover fully are the ones who keep going with the loading after it stops hurting.