The plantar aponeurosis, also known as the plantar fascia, is a strong layer of white fibrous tissue located beneath the skin on the sole of the foot.
Towards the front of the foot, at the mid-metatarsal level, it divides into five sections, each extending into a toe and straddling the flexor tendons.
Laterally, it is divided into three sections: the medial, the lateral, and the central. The central portion is the most important structurally and functionally, and is attached at its origin to the medial calcaneus (heel bone). The medial portion overlies the muscles to the hallux (big toe), while the lateral portion overlies muscles to the little toe.
During walking, the plantar aponeurosis functions mainly during "heel rise" to "toe off." It stabilizes the arch of the foot and allows flexion of the first metatarsal, enabling the first metatarsal to carry the majority of the body weight. It also provides shock absorption when the foot hits the ground.
Inflammation or injury of the plantar aponeurosis (known as plantar fasciitis) is common in athletes and will cause foot pain and may result in further leg injuries if left untreated. The condition is treated with rest, pain relievers, or in extreme cases, extracorporeal shock wave therapy.