A calcaneal spur (or heel spur) is a bony outgrowth from the calcaneal tuberosity (heel bone). Calcaneal spurs are typically detected by a radiographic examination (commonly referred to as an "x-ray"). When a foot is exposed to constant stress, calcium deposits build up on the bottom of the heel bone.
Calcaneal spurs occur when calcium deposits build up on the underside of the heel bone, a process that usually occurs over a period of many months. Heel spurs are often caused by strains on foot muscles and ligaments, stretching of the plantar fascia and repeated tearing of the membrane that covers the heel bone.
Heel spurs often cause no symptoms. But heel spurs can be associated with intermittent or chronic pain -- especially while walking, jogging, or running -- if inflammation develops at the point of the spur formation. In general, the cause of the pain is not the heel spur itself but the soft-tissue injury associated with it.
Many people describe the pain of heel spurs and plantar fasciitis as a knife or pin sticking into the bottom of their feet when they first stand up in the morning -- a pain that later turns into a dull ache. They often complain that the sharp pain returns after they stand up after sitting for a prolonged period of time.