The most common cause of heel pain is plantar fasciitis.  Many patients with plantar fasciitis have a heel spur on the front and bottom of their heel, but heel spurs do not cause pain. The common name is "heel spur" because it's easier to pronounce than "plantar fasciitis" and doctors are able to point to the spur on an x-ray. Causes of heel pain include inadequate flexibility in the calf muscles, lack of arch support, being overweight, suddenly increasing activity, and spending too much time on the feet.

Plantar fasciitis (pronounced PLAN-tar fashee-EYE-tiss) is an inflammation of the plantar fascia. "Plantar" means the bottom of the foot, "fascia" is a type of connective tissue, and "itis" means "inflammation". Heel spurs are soft, bendable deposits of calcium that are the result of tension and inflammation in the plantar fascia attachment to the heel. Heel spurs do not cause pain. They are only evidence (not proof) that a patient may have plantar fasciitis. The plantar fascia encapsulates muscles in the sole of the foot. It supports the arch of the foot by acting as a bowstring to connect the ball of the foot to the heel. When walking and at the moment the heel of the trailing leg begins to lift off the ground, the plantar fascia endures tension that is approximately two times body weight. This moment of maximum tension is increased and "sharpened" (it increases suddenly) if there is lack of flexibility in the calf muscles. A percentage increase in body weight causes the same percentage increase in tension in the fascia. Due to the repetitive nature of walking, plantar fasciitis may be a repetitive stress disorder (RSD) similar to tennis elbow.