The medical term for pain in the arch area (under the foot) is called Plantar Fasciitis, Latin for inflammation of the plantar fascia, the broad fibrous ligament that runs from the heel to the toes.
Arch pain is a very common foot problem and is often experienced when taking your first steps after getting out of bed in the morning, after long walks or prolonged periods of standing.
Arch pain occurring first in the morning is due to the fact that ligaments under the foot (Plantar Fascia) become tight and contracted during the night. After getting up in the morning with your first steps the fascia are still tight and prone to irritation when stretched. When walking or standing for long periods, the plantar fascia becomes inflamed and painful.