What is plantar fasciosis? Plantar fasciosis, or commonly known as plantar fasciitis, is pain at the attachment site of plantar fascia. The plantar fascia is a thick connective tissue stretching from the bottom of the heel along the sole of the foot to the toes. It is important for shock absorption and arch support of the foot. Plantar fasciitis is more correctly termed as “plantar fasciosis” as the underlying cause is more related to overuse ...