Plantar fasciitis is caused by the inflammation of the plantar fascia, a supporting tissue that connects the heel bone to the toe and runs across the bottom of the feet. This condition results from the injury or overuse of the foot, leading to the stretching and wearing out of the fascia. Typical symptoms of plantar fasciitis include stabbing pain and stiffness towards the heel, especially experienced in the morning or after long periods of sitting or standing.