The plantar fascia or plantar aponeurosis is the thick

connective tissue Connective tissue is one of the four primary types of animal tissue, a group of cells that are similar in structure, along with epithelial tissue, muscle tissue, and nervous tissue. It develops mostly from the mesenchyme, derived from the mesod ...

aponeurosis An aponeurosis (; : aponeuroses) is a flattened tendon by which muscle attaches to bone or fascia. Aponeuroses exhibit an ordered arrangement of collagen fibres, thus attaining high tensile strength in a particular direction while being vulnerable ...

which supports the

arch An arch is a curved vertical structure spanning an open space underneath it. Arches may support the load above them, or they may perform a purely decorative role. As a decorative element, the arch dates back to the 4th millennium BC, but stru ...

on the bottom (

plantar Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position provi ...

side) of the

foot The foot (: feet) is an anatomical structure found in many vertebrates. It is the terminal portion of a limb which bears weight and allows locomotion. In many animals with feet, the foot is an organ at the terminal part of the leg made up o ...

. Recent studies suggest that the plantar fascia is actually an

rather than true

fascia A fascia (; : fasciae or fascias; adjective fascial; ) is a generic term for macroscopic membranous bodily structures. Fasciae are classified as superficial, visceral or deep, and further designated according to their anatomical location. ...

. It runs from the tuberosity of the

calcaneus In humans and many other primates, the calcaneus (; from the Latin ''calcaneus'' or ''calcaneum'', meaning heel; : calcanei or calcanea) or heel bone is a bone of the Tarsus (skeleton), tarsus of the foot which constitutes the heel. In some other ...

(heel bone) forward to the heads of the

metatarsal bones The metatarsal bones or metatarsus (: metatarsi) are a group of five long bones in the midfoot, located between the tarsal bones (which form the heel and the ankle) and the phalanges ( toes). Lacking individual names, the metatarsal bones are ...

(the bone between each

toe Toes are the digits of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being ''digitigrade''. Humans, and other animals that walk on the soles of their feet, are described as being ''plantigrade''; ...

and the bones of the mid-foot).

Anatomy

The plantar fascia is the thick central portion of the fascia investing the plantar muscles. It extends between the medial process of the and the proximal

phalanges The phalanges (: phalanx ) are digit (anatomy), digital bones in the hands and foot, feet of most vertebrates. In primates, the Thumb, thumbs and Hallux, big toes have two phalanges while the other Digit (anatomy), digits have three phalanges. ...

of the toes. It provides some attachment to the flexor muscles of the toes. Distally, the plantar fascia becomes continuous with the fibrous sheaths enveloping the flexor tendons passing to the toes. At the anterior extremity of the sole inferior to the heads of the metatarsal bones the plantar aponeurosis forms the superficial transverse metatarsal ligament.

Structure

The plantar fascia is made up of predominantly longitudinally oriented

collagen fiber Type I collagen is the most abundant collagen of the human body, consisting of around 90% of the body's total collagen in vertebrates. Due to this, it is also the most abundant protein type found in all vertebrates. Type I forms large, eosinop ...

s. There are three distinct structural components: the medial component, the central component (plantar aponeurosis), and the lateral component (see diagram at right). The central component is the largest and most prominent.

Development

In younger people the plantar fascia is also intimately related to the

Achilles tendon The Achilles tendon or heel cord, also known as the calcaneal tendon, is a tendon at the back of the lower leg, and is the thickest in the human body. It serves to attach the plantaris, gastrocnemius (calf) and soleus muscles to the calcane ...

, with a continuous fascial connection between the two from the distal aspect of the Achilles to the origin of the plantar fascia at the calcaneal tubercle. However, the continuity of this connection decreases with age to a point that in the elderly there are few, if any, connecting fibers. There are also distinct attachments of the plantar fascia and the Achilles tendon to the

so the two do not directly contact each other. Nevertheless, there is an indirect relationship whereby if the toes are dorsiflexed, the plantar fascia tightens via the

windlass The windlass is an apparatus for moving heavy weights. Typically, a windlass consists of a horizontal cylinder (barrel), which is rotated by the turn of a crank or belt. A winch is affixed to one or both ends, and a cable or rope is wound arou ...

mechanism. If a tensile force is then generated in the Achilles tendon it will increase tensile strain in the plantar fascia. Clinically, this relationship has been used as a basis for treatment for plantar fasciitis, with stretches and night stretch splinting being applied to the /

soleus muscle In humans and some other mammals, the soleus is a powerful muscle in the back part of the lower leg (the calf). It runs from just below the knee to the heel and is involved in standing and walking. It is closely connected to the gastrocnemius mus ...

unit.

Function

The plantar fascia contributes to support of the arch of the foot by acting as a tie-rod, where it undergoes tension when the foot bears weight. One biomechanical model estimated it carries as much as 14% of the total load of the foot. In an experiment using

cadaver A cadaver, often known as a corpse, is a Death, dead human body. Cadavers are used by medical students, physicians and other scientists to study anatomy, identify disease sites, determine causes of death, and provide tissue (biology), tissue to ...

s, it was found that failure of the plantar fascia averaged at loads of (). Failure most often occurred at the proximal attachment to the calcaneus, which is consistent with the usual location of symptoms ('' i.e.'' in plantar fasciitis). Complete rupture or surgical release of the plantar fascia leads to a decrease in arch stiffness and a significant collapse of the longitudinal arch of the foot. By modeling it was predicted such conditions would result in a 17% increase in vertical displacement and a 15% increase in horizontal elongation of the foot when it was loaded at . Surgical release also significantly increases both stress in the plantar ligaments and plantar pressures under the

metatarsal The metatarsal bones or metatarsus (: metatarsi) are a group of five long bones in the midfoot, located between the tarsal bones (which form the heel and the ankle) and the phalanges ( toes). Lacking individual names, the metatarsal bones are ...

heads. Although most of the figures mentioned above are from either

studies or investigations using models, they highlight the relatively large load the plantar fascia is subjected to while contributing to the structural integrity of the foot.

Gait

The plantar fascia also has an important role in dynamic function during

gait Gait is the pattern of Motion (physics), movement of the limb (anatomy), limbs of animals, including Gait (human), humans, during Animal locomotion, locomotion over a solid substrate. Most animals use a variety of gaits, selecting gait based on s ...

. It was found the plantar fascia continuously elongated during the contact phase of gait. It went through rapid elongation before and immediately after mid-stance, reaching a maximum of elongation between mid-stance and toe-off. During this phase the plantar fascia behaves like a spring, which may assist in conserving energy. In addition, the plantar fascia has a critical role in normal mechanical function of the foot, contributing to the "

mechanism". When the toes are dorsiflexed in the propulsive phase of gait, the plantar fascia becomes tense, resulting in elevation of the longitudinal arch and shortening of the foot (see 3A). One can liken this mechanism to a cable being wound around the drum of a windlass (see 3B); the plantar fascia being the cable, the metatarsal head the drum, and the handle, the

proximal phalanx The phalanges (: phalanx ) are digital bones in the hands and feet of most vertebrates. In primates, the thumbs and big toes have two phalanges while the other digits have three phalanges. The phalanges are classed as long bones. Structu ...

Clinical significance

Plantar fasciitis

Plantar fasciitis Plantar fasciitis or plantar heel pain is a disorder of the plantar fascia, which is the connective tissue that supports the Arches of the foot, arch of the foot. It results in pain in the heel and Sole (foot), bottom of the foot that is usuall ...

is an often painful degenerative process of the plantar fascia. **

Calcaneal spur A calcaneal spur (also known as a heel spur) is a bony outgrowth from the calcaneal tuberosity (heel bone). Calcaneal spurs are typically detected by x-ray examination. It is a form of exostosis. When a foot is exposed to constant stress, calc ...

(heel spur) is a small calcified bone extension (

osteophyte Osteophytes are Exostosis, exostoses (bony projections) that form along joint margins. They are distinct from enthesophytes, which are bone, bony projections that form at the attachment of a tendon or ligament. Osteophytes are not always distingui ...

) located on the inferior aspect of the calcaneus or on the back of the heel at the insertion of the Achilles tendon. The condition is typically a response to plantar fasciitis over a period of time. It may also be related to

ankylosing spondylitis Ankylosing spondylitis (AS) is a type of arthritis from the disease spectrum of axial spondyloarthritis. It is characterized by long-term inflammation of the joints of the spine, typically where the spine joins the pelvis. With AS, eye and bow ...

, typically in children.

Other

* Plantar fibromatosis is a relatively uncommon non-malignant thickening of the plantar fascia. *

Psoriatic arthritis Psoriatic arthritis (PsA) is a long-term inflammatory arthritis that may occur in some people affected by the autoimmune disease psoriasis. The classic features of psoriatic arthritis include dactylitis (sausage-like swelling of the fingers ...

is a type of inflammatory arthritis that may affect the plantar fascia. * Plantar fascial rupture/tear is a relatively uncommon painful tearing of the plantar fascia. The tear can be full or partial.

Additional images

File:Gray443.png, alt=anatomical diagram, The plantar fascia (also known as the plantar aponeurosis) is located superficially plantar side of the foot.

References

External links

* * ()
Heel Pain Symptoms. Plantar Fasciitis diagnosis and treatment , Patient
plantar fasciitis at Patient.info {{DEFAULTSORT:Plantar Fascia Lower limb anatomy Fascia