Severs disease is the common name for a condition called calcaneal apophysitis. It really shouldn't be termed Severs “disease” as it is not a disease. This is a self limiting condition of the growth plate in the heel bone of kids which always goes away by itself sooner or later without having long term complications. This is a quite frequent ailment in children about ages 10 to 12 years and if you question a group of children of that age should they have it or have an acquaintance who has had it, then most of them probably will say yes. There exists a growth plate behind the heel bone where growth of that heel bone happens at. The achilles tendon connects to this growth area, so it is just not difficult to see that plenty of force is put on the growing area, especially if the child is overweight or active in sports activity. The ailment is a overuse of that growing region. The growing area combines with the rest of the heel bone by the early teenage years, therefore it is just not feasible for it to become a problem past that.
Whilst the Severs disease is self-limiting and they will outgrow this, it is painful and can cause discomfort so will need to be managed. The best approach is to focus on education concerning the condition and the ways to deal with activity loads to keep it manageable. It is common to use ice on the heel after sport to help settle the pain. Cushioned gel heel pads are often good and might make it more bearable to allow them to continue with activity. If you can find biomechanical problems, then proper foot orthotics may be needed to improve that. The main element of the management of Severs disease is simply managing the loads. Kids of that age want to be active and be a part of sport, so this might be a problem.