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The arches of the foot, formed by the tarsal and metatarsal bones, strengthened by
ligaments A ligament is the fibrous connective tissue that connects bones to other bones. It is also known as ''articular ligament'', ''articular larua'', ''fibrous ligament'', or ''true ligament''. Other ligaments in the body include the: * Peritoneal ...
and tendons, allow the foot to support the weight of the body in the erect posture with the least weight. They are categorized as longitudinal and transverse
arch An arch is a vertical curved structure that spans an elevated space and may or may not support the weight above it, or in case of a horizontal arch like an arch dam, the hydrostatic pressure against it. Arches may be synonymous with vau ...
es.


Structure


Longitudinal arches

The longitudinal arches of the foot can be divided into medial and lateral arches.


Medial arch

The medial arch is higher than the lateral longitudinal arch. It is made up by the calcaneus, the talus, the navicular, the three cuneiforms (medial, intermediate, and lateral), and the first, second, and third metatarsals. Its summit is at the superior articular surface of the talus, and its two extremities or piers, on which it rests in standing, are the tuberosity on the plantar surface of the calcaneus posteriorly and the heads of the first, second, and third metatarsal bones anteriorly. The chief characteristic of this arch is its elasticity, due to its height and to the number of small joints between its component parts. Its weakest part (i.e., the part most liable to yield from overpressure) is the joint between the talus and navicular, but this portion is braced by the plantar calcaneonavicular ligament a.k.a. spring ligament, which is elastic and is thus able to quickly restore the arch to its original condition when the disturbing force is removed. The ligament is strengthened medially by blending with the
deltoid ligament The deltoid ligament (or medial ligament of talocrural joint) is a strong, flat, triangular band, attached, above, to the apex and anterior and posterior borders of the medial malleolus. The deltoid ligament is composed of 4 fibers: 1. Anterior ti ...
of the ankle joint, and is supported inferiorly by the tendon of the
Tibialis posterior The tibialis posterior muscle is the most central of all the leg muscles, and is located in the deep posterior compartment of the leg. It is the key stabilizing muscle of the lower leg. Structure The tibialis posterior muscle originates on the i ...
, which is spread out in a fanshaped insertion and prevents undue tension of the ligament or such an amount of stretching as would permanently elongate it. The arch is further supported by the plantar aponeurosis, by the small muscles in the sole of the foot (short muscles of the big toe), by the tendons of the Tibialis anterior and posterior and fibularis longus, flexor digitorum longus, flexor hallucis longus and by the ligaments of all the articulations involved.


Lateral arch

The lateral arch is composed of the calcaneus, the cuboid, and the fourth and fifth metatarsals. Two notable features of this arch are its solidity and its slight elevation. Two strong ligaments, the
long plantar The long plantar ligament (long calcaneocuboid ligament; superficial long plantar ligament) is a long ligament on the underside of the foot that connects the calcaneus with the 2nd to 5th metatarsal. Structure The long plantar ligament is the ...
and the plantar calcaneocuboid, together with the Extensor tendons and the short muscles of the little toe, preserve its integrity.


Fundamental longitudinal arch

While these medial and lateral arches may be readily demonstrated as the component antero-posterior arches of the foot, the fundamental longitudinal arch is contributed to by both, and consists of the calcaneus, cuboid, third cuneiform, and third metatarsal: all the other bones of the foot may be removed without destroying this arch.


Transversal arch

In addition to the longitudinal arches the foot presents a series of transverse arches. At the posterior part of the metatarsus and the anterior part of the tarsus the arches are complete, but in the middle of the tarsus they present more the characters of half-domes, the concavities of which are directed downward and medialward, so that when the medial borders of the feet are placed in apposition a complete tarsal dome is formed. The transverse arch is composed of the three cuneiforms, the cuboid, and the five metatarsal bases. The transverse arch is strengthened by the interosseous, plantar, and dorsal ligaments, by the short muscles of the first and fifth toes (especially the transverse head of the Adductor hallucis), and by the fibularis longus, whose tendon stretches across between the piers of the arches.


Function

The medial longitudinal arch in particular creates a space for soft tissues with elastic properties, which act as springs, particularly the thick plantar aponeurosis, passing from the heel to the toes. Because of their elastic properties, these soft tissues can spread ground contact reaction forces over a longer time period, and thus reduce the risk of musculoskeletal wear or damage, and they can also store the energy of these forces, returning it at the next step and thus reducing the cost of walking and, particularly, running, where vertical forces are higher.


Clinical significance

The anatomy and shape of a person’s longitudinal and transverse arch can dictate the types of injuries to which that person is susceptible. The height of a person's arch is determined by the height of the navicular bone. Collapse of the longitudinal arches results in what is known as flat feet. A person with a low longitudinal arch, or flat feet will likely stand and walk with their feet in a pronated position, where the foot everts or rolls inward. This makes the person susceptible to heel pain, arch pain and plantar fasciitis. Flat footed people may also have more difficulty performing exercises that require supporting their weight on their toes. People who have high longitudinal arches or a cavus foot tend to walk and stand with their feet in a supinated position where the foot inverts or rolls outward. High arches can also cause plantar fasciitis as they cause the plantar fascia to be stretched away from the calcaneus or heel bone. Additionally, high or low arches can increase the risk of shin splints as the anterior tibialis must work harder to keep the foot from slapping the ground.


Evolution and other animals

The non-
human Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, cultu ...
apes (the gibbons,
gorilla Gorillas are herbivorous, predominantly ground-dwelling great apes that inhabit the tropical forests of equatorial Africa. The genus ''Gorilla'' is divided into two species: the eastern gorilla and the western gorilla, and either four ...
s,
orangutan Orangutans are great apes native to the rainforests of Indonesia and Malaysia. They are now found only in parts of Borneo and Sumatra, but during the Pleistocene they ranged throughout Southeast Asia and South China. Classified in the genu ...
s,
chimpanzee The chimpanzee (''Pan troglodytes''), also known as simply the chimp, is a species of great ape native to the forest and savannah of tropical Africa. It has four confirmed subspecies and a fifth proposed subspecies. When its close relative t ...
s and
bonobo The bonobo (; ''Pan paniscus''), also historically called the pygmy chimpanzee and less often the dwarf chimpanzee or gracile chimpanzee, is an endangered great ape and one of the two species making up the genus '' Pan,'' the other being the comm ...
s) tend to walk on the lateral side of the foot, that is with an 'inverted' foot, which may reflect a basic adaptation to walking on branches. It is often held that their feet lack longitudinal arches, but footprints made by bipedally walking apes, which must directly or indirectly reflect the pressure they exert to support and propel themselves do suggest that they exert lower foot pressure under the medial part of their midfoot. However, human feet, and the human medial longitudinal arch, differ in that the anterior part of the foot is medially twisted on the posterior part of the foot, so that all the toes may contact the ground at the same time, and the twisting is so marked that the most medial toe, the big toe or hallux, (in some individuals the second toe) tends to exert the greatest propulsive force in walking and running. This gives the human foot an 'everted' or relatively outward-facing appearance compared to that of other apes. The strong twisting of the anterior part of the human foot on the posterior part tends to increase the height of the medial longitudinal arch. However, there is now considerable evidence that shoe-wearing also accentuates the height of the medial longitudinal arch and that the height of the medial longitudinal arch also differs very considerably between individuals and at different speeds. The presence of high-arched feet in modern humans is a result of natural selection for long distance running. On the other hand, the primitive trait of arch-less feet in our great ape relatives has been maintained because of selection for grasping tree branches as a part of their arboreal lifestyle. Divergence between ape feet and human feet began with the early human ancestor '' Ardipithecus ramidus'', when strengthened plantar tissue evolved, which supported early terrestrial propulsion before evolving a true arch. However, the skeletal longitudinal arch structure itself did not begin to evolve until ''
Australopithecus afarensis ''Australopithecus afarensis'' is an extinct species of australopithecine which lived from about 3.9–2.9 million years ago (mya) in the Pliocene of East Africa. The first fossils were discovered in the 1930s, but major fossil finds would no ...
'' had evolved a relatively low longitudinal arch (compared to modern humans) and the first signs of a transverse arch accompanying it. It is not yet agreed to what extent the early human ancestor ''
Australopithecus afarensis ''Australopithecus afarensis'' is an extinct species of australopithecine which lived from about 3.9–2.9 million years ago (mya) in the Pliocene of East Africa. The first fossils were discovered in the 1930s, but major fossil finds would no ...
'', (3.75 million years ago onwards) had acquired a functionally human-like foot, but the medial twist of the forefoot evident in fossil footbones of this species, and in the Laetoli footprint trail in Tanzania generally attributed to this species, certainly appears less marked than is evident in fossil footbones of ''
Homo erectus ''Homo erectus'' (; meaning "upright man") is an extinct species of archaic human from the Pleistocene, with its earliest occurrence about 2 million years ago. Several human species, such as '' H. heidelbergensis'' and '' H. antecessor ...
'' (sometimes called '' Homo georgicus'') from Dmanisi, Georgia (c. 1. 8 million years ago) and the roughly contemporaneous fossil footprint trail at
Ileret Ileret (also spelled Illeret) is a village in Marsabit County, Kenya. It is located in Northern Kenya, on the eastern shore of Lake Turkana, north of Sibiloi National Park and near the Ethiopian border. Numerous hominin fossils have been found ...
, Kenya attributed to '' Homo erectus ergaster''.


See also

* Pes cavus * Flat feet *
Arch support A removable shoe insert, otherwise known as a foot orthosis, insole or inner sole accomplishes many purposes, including daily wear comfort, height enhancement, plantar fasciitis treatment, arch support, foot and joint pain relief from arthritis, ...
*
Comparison of orthotics Comparison of orthotics stem from podiatrists having molded custom orthotics to address patients' foot malformations. Over the years they have developed numerous means to create the basis for their molds, plaster casts, foam box impressions, or thr ...
* Foot gymnastics


References


Bibliography

* * * * * * * * *


External links


Overview at gla.ac.uk



Arches of the foot
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