What is plantar fasciitis? The plantar fascia is a thick band of fibrous tissue that runs from the heel bone to the base of the toes. Inflammation at the site where the fibrous plantar fascia joins the heel bone is known as plantar fasciitis. Some experts believe small degenerative tears occur, and the tear is followed by inflammation. The plantar fascia is gristly, like the white sinew on a leg of lamb. This means it does not have much in the...