Structure
The plantar aponeurosis is a thick collagenous structure located deep to the superficial fascia and the skin of the sole of the foot. It is composed of mainly longitudinally arranged fibers, along with some transverse fibers.
The central part of the plantar aponeurosis is the strongest, extending from the medial process of the calcaneal tuberosity to the digits. Along the shafts of the metatarsal bones, the plantar aponeurosis divides into five bands, which extend into each digit to become continuous with the fibrous sheaths of the toes. These digital bands are connected proximally via transverse fibers. Each digit band connects to the dermis of the skin via the retinacula cutis, or skin ligaments. This anchors the skin to the underlying deep fascia and gives the sole of the foot extra grip (Moore, Dalley and Agur, 2013). Additionally, the digital bands are reinforced by the superficial transverse metatarsal ligament.
The lateral part of the plantar aponeurosis is the lateral continuation of the plantar aponeurosis. It is thin distally, but thicker distally where it attaches to the calcaneus. It overlies the abductor digiti minimi muscle and is continuous with the dorsal fascia of the foot laterally.
The medial part of the plantar aponeurosis is the medial continuation of the plantar aponeurosis. It is thin throughout and overlies the abductor hallucis muscle. It is continuous medially with the dorsal fascia of the foot.
Related parts of the anatomy
Anatomical Relations
In the midfoot and forefoot, at the point where the central part of the plantar aponeurosis meets the medial and lateral parts, two vertical intermuscular septa extend deeply towards the first and fifth metatarsals. This divides the sole of the foot into three muscular compartments.
—The medial compartment is covered by the medial part of the plantar aponeurosis and contains the abductor hallucis, flexor hallucis brevis, and the tendon of the flexor hallucis longus muscle.
—The central (or intermediate) compartment is covered by the central part of the plantar aponeurosis and contains flexor digitorum brevis muscle, the tendons of the flexor digitorum longus muscle, the lumbricals, quadratus plantae, adductor hallucis muscle.
—The lateral compartment is covered by the lateral part of the plantar aponeurosis and contains the abductor digiti minimi and flexor digiti minimi brevis muscles.
In the forefoot, an additional interosseous compartment contains the plantar and dorsal interossei surrounded by an interosseous fascia. The metatarsal bones are contained within this compartment.
Function
The plantar aponeurosis helps hold the structures of the foot together, while supporting the longitudinal arches of the foot.
List of Clinical Correlates
—Plantar fasciitis
References
Moore, K. L., Dalley, A. F. and Agur, A. M. R. (2013) Clinically Oriented Anatomy. Clinically Oriented Anatomy 7th edn.: Wolters Kluwer Health/Lippincott Williams & Wilkins.
