It can be extremely painful for kids who have this and it can often cause a lot of concern for parents.
Let me start by reassuring you this is probably the most common cause of foot pain that I see in the under-16s.
When we are growing, the bones grow from regions called growth plates. These regions become 'active' during growth spurts, and are more suscepitble to irritation. As a result, sporty and active children will continue running around on this easily irritated structure and it can cause them severe pain.
There is no good reason to stop doing sports, but a careful balance of monitoring activity levels is important.
A type of heel pain, also known as 'Sever's Disease'. This is a condition that affects children who have typically had growth spurts or are incredibly active.