Sever's disease (also called calcaneal apophysitis), is the most common cause of heel pain in childhood and adolescence. It is thought to be an overuse syndrome caused by repetitive microtrauma. This is the result of increased pulling by the calf muscles onto the heel, through the Achilles tendon. This puts pressure on the growth plate in the heel bone. Small avulsion - or pulling - fractures occur followed by inflammation in that area. It is more common in young people who play a lot of sport.
This is a companion discussion topic for the original article at https://patient.info/childrens-health/severs-disease-leaflet