Arches of the foot

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Arches of the foot
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Skeleton of foot. Medial aspect.
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Skeleton of foot. Lateral aspect.
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Identifiers
Latin arcus pedis
Anatomical terminology

The arches of the foot, formed by the tarsal and metatarsal bones, strengthened by ligaments and tendons, allow the foot to support the weight of the body in the erect posture with the least weight.

Contents

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. [1]

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. [1]

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. [1]

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 of the ankle joint, and is supported inferiorly by the tendon of the tibialis posterior, 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. [1]

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. [1]

Lateral arch

The lateral arch is composed of the calcaneus, the cuboid, and the fourth and fifth metatarsals. [1]

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 and the short muscles of the little toe, preserve its integrity. [1]

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. [1]

Transversal arch

Cross section of feet showing metatarsal bones forming anterior arch: A = normal position, B = flattened arch Foot care and shoe fitting-Fig5 Cross section of feet showing metatarsal bones forming anterior arch.png
Cross section of feet showing metatarsal bones forming anterior arch: A = normal position, B = flattened arch

In addition to the longitudinal arches the foot presents a series of transverse arches. [1]

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. [1]

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. [2]

Clinical significance

Arched feet are generally more common in men, and studies have reported that women are more likely to have flat feet than men. [3] Women who do have arched feet who experience pregnancy and may experience a flattening of their arched feet, as the surge of female sex hormones such as estrogen can cause the tendons in their feet to soften and relax, to the extent that their arched feet become flat. [4]

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. [5] 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. [6] 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 [7] 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. [8]

Evolution and other animals

The non-human apes (the gibbons, gorillas, orangutans, chimpanzees and bonobos) tend to walk on the lateral side of the foot, that is with an 'inverted' foot, [9] 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 [10] [11] 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, [12] 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 [13] and that the height of the medial longitudinal arch also differs very considerably between individuals and at different speeds. [14]

The presence of high-arched feet in modern humans is a result of natural selection for long-distance running. [15] 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. [16] 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. [17] However, the skeletal longitudinal arch structure itself did not begin to evolve until Australopithecus afarensis had evolved a relatively low longitudinal arch (compared to modern humans) and the first signs of a transverse arch accompanying it. [17]

It is not yet agreed to what extent the early human ancestor Australopithecus afarensis , (3.75 million years ago onwards) had acquired a functionally human-like foot, [9] 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 (sometimes called Homo georgicus ) from Dmanisi, Georgia (c. 1. 8 million years ago) [18] and the roughly contemporaneous fossil footprint trail at Ileret, Kenya attributed to Homo erectus ergaster . [19]

See also

Related Research Articles

<span class="mw-page-title-main">Foot</span> Anatomical structure found in vertebrates

The foot 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 a separate organ at the terminal part of the leg made up of one or more segments or bones, generally including claws and/or nails.

<span class="mw-page-title-main">Human leg</span> Lower extremity or limb of the human body (foot, lower leg, thigh and hip)

The leg is the entire lower limb of the human body, including the foot, thigh or sometimes even the hip or buttock region. The major bones of the leg are the femur, tibia, and adjacent fibula. The thigh is between the hip and knee, while the calf (rear) and shin (front) are between the knee and foot.

<span class="mw-page-title-main">Fibularis longus</span> Superficial muscle in the lateral compartment of the leg

In human anatomy, the fibularis 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 downward away from the body at the ankle.

<span class="mw-page-title-main">Cuboid bone</span> Bone of the ankle

In the human body, the cuboid bone is one of the seven tarsal bones of the foot.

<span class="mw-page-title-main">Ankle</span> Region where the foot and the leg meet

The ankle, the talocrural region or the jumping bone (informal) is the area where the foot and the leg meet. The ankle includes three joints: the ankle joint proper or talocrural joint, the subtalar joint, and the inferior tibiofibular joint. The movements produced at this joint are dorsiflexion and plantarflexion of the foot. In common usage, the term ankle refers exclusively to the ankle region. In medical terminology, "ankle" can refer broadly to the region or specifically to the talocrural joint.

<span class="mw-page-title-main">Calcaneus</span> Bone of the tarsus of the foot

In humans and many other primates, the calcaneus or heel bone is a bone of the tarsus of the foot which constitutes the heel. In some other animals, it is the point of the hock.

<span class="mw-page-title-main">Plantar fascia</span> Aponeurosis of the sole of the foot

The plantar fascia or plantar aponeurosis is the thick connective tissue aponeurosis which supports the arch on the bottom of the foot. Recent studies suggest that the plantar fascia is actually an aponeurosis rather than true fascia. It runs from the tuberosity of the calcaneus forward to the heads of the metatarsal bones.

<span class="mw-page-title-main">Flat feet</span> Foot arch deformity

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 with flat feet (congenital). There is a functional relationship between the structure of the arch of the foot and the biomechanics of the lower leg. The arch provides an elastic, springy connection between the forefoot and the hind foot so that a majority of the forces incurred during weight bearing on the foot can be dissipated before the force reaches the long bones of the leg and thigh.

<span class="mw-page-title-main">Tibialis anterior muscle</span> Flexor muscle in humans that dorsiflexes the foot

The tibialis anterior muscle is a muscle of the anterior compartment of the lower leg. It originates from the upper portion of the tibia; it inserts into the medial cuneiform and first metatarsal bones of the foot. It acts to dorsiflex and invert the foot. This muscle is mostly located near the shin.

<span class="mw-page-title-main">Talus bone</span> One of the foot bones that forms the tarsus

The talus, talus bone, astragalus, or ankle bone is one of the group of foot bones known as the tarsus. The tarsus forms the lower part of the ankle joint. It transmits the entire weight of the body from the lower legs to the foot.

<span class="mw-page-title-main">Dorsal interossei of the foot</span> Four muscles situated between the metatarsal bones

In human anatomy, the dorsal interossei of the foot are four muscles situated between the metatarsal bones.

<span class="mw-page-title-main">Fibularis brevis</span> Shorter and smaller of the fibularis (peroneus) muscles

In human anatomy, the fibularis brevis is a muscle that lies underneath the fibularis longus within 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 downward away from the body at the ankle.

<span class="mw-page-title-main">Flexor hallucis brevis muscle</span> Muscle in sole of the foot that leads to the big toe

Flexor hallucis brevis muscle is a muscle of the foot that flexes the big toe.

<span class="mw-page-title-main">Quadratus plantae muscle</span> Muscles of the sole of the foot

The quadratus plantae is separated from the muscles of the first layer by the lateral plantar vessels and nerve. It acts to aid in flexing the 2nd to 5th toes and is one of the few muscles in the foot with no homolog in the hand.

<span class="mw-page-title-main">Sole (foot)</span> Bottom part of foot

In humans, the sole of the foot is anatomically referred to as the plantar aspect.

<span class="mw-page-title-main">Talocalcaneonavicular joint</span>

The talocalcaneonavicular joint is a ball and socket joint in the foot; the rounded head of the talus is received into the concavity formed by the posterior surface of the navicular, the anterior articular surface of the calcaneus, and the upper surface of the plantar calcaneonavicular ligament.

<span class="mw-page-title-main">Plantar calcaneonavicular ligament</span> Ligaments on the underside of the foot

The plantar calcaneonavicular ligament is a complex of three ligaments on the underside of the foot that connect the calcaneus with the navicular bone.

<span class="mw-page-title-main">Fifth metatarsal bone</span> Long bone in the foot

The fifth metatarsal bone is a long bone in the foot, and is palpable along the distal outer edges of the feet. It is the second smallest of the five metatarsal bones. The fifth metatarsal is analogous to the fifth metacarpal bone in the hand.

<span class="mw-page-title-main">First metatarsal bone</span>

The first metatarsal bone is the bone in the foot just behind the big toe. The first metatarsal bone is the shortest of the metatarsal bones and by far the thickest and strongest of them.

In the human foot, the plantar or volar plates are fibrocartilaginous structures found in the metatarsophalangeal (MTP) and interphalangeal (IP) joints. The anatomy and composition of the plantar plates are similar to the palmar plates in the metacarpophalangeal (MCP) and interphalangeal joints in the hand; the proximal origin is thin but the distal insertion is stout. Due to the weight-bearing nature of the human foot, the plantar plates are exposed to extension forces not present in the human hand.

References

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