Plantar fasciitis is an inflammation of the fibrous tissue of the plantar fascia. The pain is often localized in the heel and along the sole of the foot. Plantar fasciitis can be the consequence of weight gain, dehydration, or a change in physical activity. Plantar fasciitis is treated by deep massage and a series of flexion and extension foot exercises practiced with a physical therapist. A pain killer helps calm the pain in severe cases.