The arches of the foot, formed by the tarsal and

metatarsal The metatarsal bones, or metatarsus, are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the me ...

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 l ...

and

tendons A tendon or sinew is a tough, high-tensile-strength band of dense fibrous connective tissue that connects muscle to bone. It is able to transmit the mechanical forces of muscle contraction to the skeletal system without sacrificing its ability ...

, 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 arches.

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 navicular bone is a small bone found in the feet of most mammals. Human anatomy The navicular bone in humans is one of the tarsal bones, found in the foot. Its name derives from the human bone's resemblance to a small boat, caused by th ...

, the three cuneiforms (medial, intermediate, and lateral), and the first, second, and third

metatarsals The metatarsal bones, or metatarsus, are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the me ...

. 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 The plantar calcaneonavicular ligament (also known as the spring ligament or spring ligament complex) is a complex of three ligaments on the underside of the foot that connect the calcaneus with the navicular bone. Structure The plantar calcan ...

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 t ...

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 ...

, 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 The tibialis anterior muscle is a muscle in humans that originates along the upper two-thirds of the lateral (outside) surface of the tibia and inserts into the medial cuneiform and first metatarsal bones of the foot. It acts to dorsiflex and inve ...

and posterior and

fibularis longus In human anatomy, the fibularis longus (also known as peroneus longus) is a superficial muscle in the lateral compartment of the leg. It acts to tilt the sole of the foot away from the midline of the body ( eversion) and to extend the foot downwar ...

, 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 and the plantar calcaneocuboid, together with the

Extensor tendons In anatomy, extension is a movement of a joint that increases the angle between two bones or body surfaces at a joint. Extension usually results in straightening of the bones or body surfaces involved. For example, extension is produced by extendin ...

and the short muscles of the

little toe Toes are the digits (fingers) 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 '' pl ...

, 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

Foot care and shoe fitting-Fig5 Cross section of feet showing metatarsal bones forming anterior 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 The Adductor hallucis (Adductor obliquus hallucis) arises by two heads—oblique and transverse and is responsible for adducting the big toe. It has two heads, both are innervated by the lateral plantar nerve. Structure Oblique head The ''oblique ...

), and by the

, 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 tissue Soft tissue is all the tissue in the body that is not hardened by the processes of ossification or calcification such as bones and teeth. Soft tissue connects, surrounds or supports internal organs and bones, and includes muscle, tendons, ...

s 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 Flat feet (also called pes planus or fallen arches) is a postural deformity in which the arches of the foot collapse, with the entire sole of the foot coming into complete or near-complete contact with the ground. Sometimes children are born ...

. 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 Plantar fasciitis or plantar heel pain (PHP) is a disorder of the plantar fascia, which is the connective tissue which supports the arch of the foot. It results in pain in the heel and bottom of the foot that is usually most severe with the fi ...

. 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 ...

ape Apes (collectively Hominoidea ) are a clade of Old World simians native to sub-Saharan Africa and Southeast Asia (though they were more widespread in Africa, most of Asia, and as well as Europe in prehistory), which together with its sister g ...

s (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 or fi ...

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, chimpanzees and bonobos) 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 ''Ardipithecus ramidus'' is a species of australopithecine from the Afar region of Early Pliocene Ethiopia 4.4 million years ago (mya). ''A. ramidus'', unlike modern hominids, has adaptations for both walking on two legs ( bipedality) and life i ...

'', 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 not ...

'' 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 ''

'', (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 Laetoli is a pre-historic site located in Enduleni ward of Ngorongoro District in Arusha Region, Tanzania. The site is dated to the Plio-Pleistocene and famous for its Hominina footprints, preserved in volcanic ash. The site of the Laetoli fo ...

footprint trail in Tanzania generally attributed to this species, certainly appears less marked than is evident in fossil footbones of '' Homo erectus'' (sometimes called ''

Homo georgicus The Dmanisi hominins, Dmanisi people, or Dmanisi man were a population of Early Pleistocene hominins whose fossils have been recovered at Dmanisi, Georgia. The fossils and stone tools recovered at Dmanisi range in age from 1.85–1.77 million y ...

'') from

Dmanisi Dmanisi ( ka, დმანისი, tr, , az, Başkeçid) is a town and archaeological site in the Kvemo Kartli region of Georgia approximately 93 km southwest of the nation’s capital Tbilisi in the river valley of Mashavera. The hominin ...

, 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 foun ...

, Kenya attributed to '' Homo erectus ergaster''.

References

Bibliography

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External links

Overview at gla.ac.uk

Arches of the foot
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