What is plantar Faciitis? The plantar fascia is the tissue under the foot which forms the arch. When over-used and over-stretched the tissue often becomes sore, thickened and inflamed. Symptoms of plantar fasciitis present as a gradual onset of pain under the heel which may radiate forwards into the foot towards the base of the big toe. Symptoms come on gradually and are often worse first thing in the morning. There are a number of factors which can increase the likelihood of