The most common condition that causes pain at the bottom of the heel is plantar fascitis. The plantar fascia is a strong ligament-like structure that attaches to the heel and courses along the arch of the foot, inserting into the base of the toes. The plantar fascia contributes to the support of the longitudinal arch. With every step this structure tenses, then relaxes. The pain is due to inflammation where the fascia attaches to the heel bone.
Symptoms tend to be worse in the morning or after prolonged sitting.
The repetitive stretching of the plantar fascia over years may lead to the development of a bone spur. In point of fact, there are patients with this condition who do not have a bone spur on X-ray. Conversely, there are patients who have X-rays of the foot taken for reasons other than heel pain who have large bone spurs. Recently, a small nerve called the abductor digiti quinti nerve has been identified that courses close to the plantar fascia. Some believe that irritation of this nerve may be the sole cause or a contributing factor to the development of heel pain.