It can be quite serious. The so-called "heel bone", when broken, can cause a lot of pain, and prevent you from walking, so it can be a real life changer. It is, however, not fatal. I changed the original answer from calcanium which, if you really meant calcaneum is a protrusion from the tarsus extant in bird but not humans.
Calcaneus
The calcaneus.
The talus bone sits on the calcaneus.
The calcaneus is the name for the bone that makes the heel. It forms a large bulbous projection from the posterior and inferior part of the foot to which the calcaneal tendon (or Achilles tendon) attaches.
The calcaneus is the "heel". It is one of the tarsal bones in the foot.
The calcaneus is the "heel". It is one of the tarsal bones in the foot.
The largest tarsal bone in the human body is the calcaneus, or heel bone.
In talipes calcaneus, the foot points upward, with the heel pointing down
The Achilles tendon structure joins the gastrocnemius to the calcaneus.
A really bad hunter on World of Warcraft located in Shattered halls.
A thickening on the surface of the calcaneus bone is usually a heel spur.
calcaneal