The calcaneus (heel bone) is a big bone that forms the back of the foot’s foundation. A heel spur is a bony protrusion that develops over time between the heel bone and the arch of the heel as a result of calcium deposition. A heel spur can extend up to half an inch forward.
Plantar fasciitis is the name for the irritation that occurs as a result of this ailment (or inflammation of the fibrous connective tissue in the foot called plantar fascia).
The source of discomfort in people with a heel spur is not the spur itself, but the damage to soft tissue that results from it. A heel spur is not the only cause of heel discomfort, despite popular belief.