In most cases, it is not the spur that causes heel pain. Heel pain can be present with or without evidence of a heel spur on x-ray of the foot. The same stretching and tearing that can lead to the formation of a spur causes microtears and degeneration of the plantar fascia, the long fibrous band that connects the heel to the ball of the foot and supports the longitudinal arch. The resulting inflammation, called plantar fasciitis, makes the area painful after periods of rest which allow the fascia to heel in a relaxed, rather than in a flexed position. Heel pain attributed to plantar fasciitis is generally due to too much stress on the heel and the soft tissues connecting to it, including the plantar fascia.
Several factors can contribute to the amount of stress placed on the tissues.
Stress on plantar fascia is increased when these activities are performed regularly or when they are begun abruptly after long periods of physical inactivity. There can also be atrophy of the fat pad covering the heel resulting in decreased shock absorbency. Regularly wearing high-heel shoes can lead to shortening of the Achilles tendon, which increases the strain on your heels and fascia when you change to a flatter shoe. There may also be some activity related discomfort throughout the day. Most people experience the pain in only one foot, although it can occur in both.