Plantar fasciitis is a painful inflammatory process of the plantar fascia. The plantar fascia is the connective tissue on the sole of the foot. Most people with plantar fasciitis have pain when they take their first steps out of bed, sitting for a long period of time, climbing the stairs and/or after intense activates. This is due to the tightening of the fascia ligament. Pain can occur under or on the side of the heel around the insertion of the ligament.