Heel stress fractures are caused by high impact, high intensity and long duration activities. The best way to appreciate what the stress fracture is, is to visualise it. Looking at the picture above on the right gives a good estimation of what it looks like. The way in which it fractures can variate in many ways; length, dept and point of fracture on the heel bone.
This type of heel pain can be intense and requires offloading and plenty of rest. In order to diagnose the stress fracture you will be referred to get a Xray. The Xray will be able to see the extent of damage and its exact location. There are other factors, such as the environment, bone composition and even training executed in a improper way can cause for heel stress fractures.
Bone takes approximately 6-8 weeks to heal depending on your health status.