Wiktionary
plantar fascia
n. The thick connective tissue which supports the arch of the foot.
Wikipedia
Plantar fascia
The plantar fascia is the thick connective tissue ( aponeurosis) which supports the arch on the bottom ( plantar side) of the foot. It runs from the tuberosity of the calcaneus (heel bone) forward to the heads of the metatarsal bones (the bone between each toe and the bones of the mid-foot).