The plantar fascia or plantar aponeurosis is a dense collection of collagen fibers on the sole (plantar surface) of the foot. These fibers are mostly longitudinal but also transverse.
Gross anatomy
Posteriorly it attaches to the medial process of the tuberosity of the calcaneus, proximal to flexor digitorum brevis. It is narrow and thick at this attachment and becomes more broad and thin distally and anteriorly.
Proximally, there are three bands 3:
medial band
central band
lateral band
The medial band inserts into the 1st metatarsophalangeal joint. The lateral band inserts into the base of the 5th metatarsal. The central band is largest, and anteriorly it divides into five heads, one for each toe, just proximal to the heads of the metatarsals. The superficial layers of these fibers insert into the dermis at the ball of the foot and the crease between the ball and the toes via the retinacula cutis (skin ligaments). The deep layers of each digit become septa that separate the digital flexor tendons from the lumbricals and the digital vessels and nerves.
Laterally it covers abductor digiti minimi.
Medially it covers abductor hallucis and merges with the flexor retinaculum and dorsalis pedis fascia.