Achilles tendon

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Achilles tendon
1123 Muscles of the Leg that Move the Foot and Toes b.png
The Achilles tendon or calcaneal tendon is attached to the gastrocnemius and soleus muscles.
Details
LocationBack of the lower leg
Identifiers
Latin tendo calcaneus, tendo Achillis
MeSH D000125
TA98 A04.7.02.048
TA2 2662
FMA 51061
Anatomical terminology

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. [1] [2] [3] [4] [5] [6] [7] It serves to attach the plantaris, gastrocnemius (calf) and soleus muscles to the calcaneus (heel) bone. These muscles, acting via the tendon, cause plantar flexion of the foot at the ankle joint, and (except the soleus) flexion at the knee.

Contents

Abnormalities of the Achilles tendon include inflammation (Achilles tendinitis), degeneration, rupture, and becoming embedded with cholesterol deposits (xanthomas).

The Achilles tendon was named in 1693 after the Greek hero Achilles. [8]

Structure

The achilles tendon, tendo calcaneus attaches distally to the calcaneual tuberosity, and arises superiorly from the triceps surae complex of the gastrocnemius and soleus muscles. 1124 Intrinsic Muscles of the Foot a.png
The achilles tendon, tendo calcaneus attaches distally to the calcaneual tuberosity, and arises superiorly from the triceps surae complex of the gastrocnemius and soleus muscles.
Achilles tendon at foetus Achilles tendon of foetus.jpg
Achilles tendon at foetus

The Achilles tendon connects muscle to bone, like other tendons, and is located at the back of the lower leg. The Achilles tendon connects the gastrocnemius and soleus muscles to the calcaneal tuberosity on the calcaneus (heel bone). [9] The tendon begins near the middle of the calf, and receives muscle fibers on its inner surface, particularly from the soleus muscle, almost to its lower end. Gradually thinning below, it inserts into the middle part of the back of the calcaneus bone. The tendon spreads out somewhat at its lower end so that its narrowest part is about 4 cm (1.6 in) above its insertion. [10]

The tendon is covered by the fascia and skin, and stands out prominently behind the bone; the gap is filled up with areolar and adipose tissue. A bursa lies between the tendon and the upper part of the calcaneus. It is about 15 centimetres (6 in) long. Along the side of the muscle, and superficial to it, is the small saphenous vein. The sural nerve accompanies the small saphenous vein as it descends in the posterior leg, traveling inferolateral to it as it crosses the lateral border of the Achilles tendon. [11] The tendon is the thickest tendon in the human body. [10] It can receive a load stress 3.9 times body weight during walking and 7.7 times body weight when running. [12]

The blood supply to the Achilles tendon is poor, and mostly via a recurrent branch of the posterior tibial artery, and some through arterial branches passing through surrounding muscles. [10]

Function

Acting via the Achilles tendon, the gastrocnemius and soleus muscles cause plantar flexion of the foot at the ankle. This action brings the sole of the foot closer to the back of the leg. The gastrocnemius also flexes the leg at the knee. Both muscles are innervated by the tibial nerve. [13] Because the fibres of the tendon spiral about 90 degrees, fibres from the gastrocnemius tend to attach to the outer part of the bone, whereas fibres from the soleus tend to attach closer to the midline. [10]

Vibration of the tendon without vision has a major impact on postural orientation. [14] Vibration of the tendon causes movement backwards and the illusion of a forward body tilt in standing subjects. [15] This is because vibrations stimulate muscle spindles in the calf muscles. The muscle spindles alert the brain that the body is moving forward, so the central nervous system compensates by moving the body backwards.

Clinical significance

Inflammation

Inflammation of the Achilles tendon is called Achilles tendinitis. Achilles tendinosis is the soreness or stiffness of the tendon, particularly worse when exercising, and generally due to overuse. [16] The most common symptoms are pain and swelling around the affected tendon. [17] The pain is typically worse at the start of exercise and decreases thereafter. [18] Stiffness of the ankle may also be present. [19] Onset is generally gradual. [17]

It commonly occurs as a result of overuse such as running. [19] [18] Other risk factors include trauma, a lifestyle that includes little exercise, high-heel shoes, rheumatoid arthritis, and medications of the fluoroquinolone or steroid class. [17] Diagnosis is generally based on symptoms and examination. [18]

While stretching and exercises to strengthen the back are often recommended for prevention, evidence to support these measures is poor. [20] [21] [22] Treatment typically involves rest, ice, non-steroidal antiinflammatory agents (NSAIDs), and physical therapy. [17] [19] A heel lift or orthotics may also be helpful. [19] [18] In those in who symptoms last more than six months despite other treatments, surgery may be considered. [19] Achilles tendinitis is relatively common. [19]

Degeneration

Achilles tendon degeneration (tendinosis) is typically investigated with either MRI or ultrasound. In both cases, the tendon is thickened, may demonstrate surrounding inflammation by virtue of the presence of paratenonitis, retrocalcaneal or retro-achilles bursitis. Within the tendon, increased blood flow, tendon fibril disorganisation, and partial thickness tears may be identified. Achilles tendinosis frequently involves the mid portion of the tendon but may involve the insertion, which is then known as enthesopathy. Though enthesopathy may be seen in the context of advancing age, it is also associated with arthritis such as gout and the seronegative spondyloarthitides. Achilles tendinosis is a known risk factor for calf muscle tears. [23]

Rupture

Achilles tendon rupture is when the Achilles tendon breaks. [24] Symptoms include the sudden onset of sharp pain in the heel. [17] A snapping sound may be heard as the tendon breaks and walking becomes difficult. [25]

Rupture typically occurs as a result of a sudden bending up of the foot when the calf muscle is engaged, direct trauma, or long-standing tendonitis. [25] [24] Other risk factors include the use of fluoroquinolones, a significant change in exercise, rheumatoid arthritis, gout, or corticosteroid use. [26] [24] Diagnosis is typically based on symptoms and examination and supported by medical imaging. [24] Achilles tendon rupture occurs in about 1 per 10,000 people per year. [24] Males are more commonly affected than females. [26] People in their 30s to 50s are most commonly affected. [24]

Prevention may include stretching before activity. [25] Treatment may be by surgery or casting with the toes somewhat pointed down. [27] [24] Relatively rapid return to weight bearing (within 4 weeks) appears okay. [27] [28] The risk of re-rupture is about 25% with casting. [24] If appropriate treatment does not occur within 4 weeks of the injury outcomes are not as good. [29]

Xanthomas

Tendon xanthomas are cholesterol deposits that commonly develop in the Achilles tendon of people with lipid metabolism disorders such as familial hypercholesterolemia. [30]

Neurological exam

The Achilles' tendon is often tested as part of a neurological examination. In this examination, the tendon is hit with a tendon hammer. This tests the S1 and S2 spinal nerves: a normal response is plantar flexion (downward movement) of the foot. [31]

Level or portion of tendon affected [32]

Other animals

The Achilles tendon is short or absent in great apes, but long in arboreal gibbons and humans. [36] It provides elastic energy storage in hopping, [37] walking, and running. [36] Computer models suggest this energy storage Achilles tendon increases top running speed by >80% and reduces running costs by more than three-quarters. [36] It has been suggested that the "absence of a well-developed Achilles tendon in the nonhuman African apes would preclude them from effective running, both at high speeds and over extended distances." [36]

History

The oldest-known written record of the tendon being named for Achilles is in 1693 by the Flemish/Dutch anatomist Philip Verheyen. In his widely used text Corporis Humani Anatomia he described the tendon's location and said that it was commonly called "the cord of Achilles." [38] [39] The tendon has been described as early as the time of Hippocrates, who described it as the "tendo magnus" (Latin for "great tendon") and by subsequent anatomists prior to Verheyen as "chorda Hippocratis" (Latin for "Hippocrates' string"). [39]

Verheyen referred to the mythological account of Achilles being held by the heel by his mother Thetis when she dipped him in the River Styx as a baby to render his body invulnerable. As the heel by which she held him was not touched by the water, it was his one vulnerable spot (hence the expression "Achilles' heel") and he was eventually killed by a poison dart to the heel. The name thus also refers to the particularly disabling and painful effect of an injury to this tendon. [39] The first closed rupture was described by Ambroise Pare in the sixteenth century. [39]

The Achilles tendon is also known as the "tendo calcaneus" (Latin for "calcaneal tendon"). [39] Because eponyms (names relating to people) have no relationship to the subject matter, most anatomical eponyms also have scientifically descriptive terms. The term calcaneal comes from the Latin calcaneum, meaning heel.

See also

Related Research Articles

Foot 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 or nails.

Human leg Lower extremity or limb of the human body (foot, lower leg, thigh and hip)

The human leg, in the general word sense, is the entire lower limb of the human body, including the foot, thigh and even the hip or gluteal region. However, the definition in human anatomy refers only to the section of the lower limb extending from the knee to the ankle, also known as the crus or, especially in non-technical use, the shank. Legs are used for standing, and all forms of locomotion including recreational such as dancing, and constitute a significant portion of a person's mass. Female legs generally have greater hip anteversion and tibiofemoral angles, but shorter femur and tibial lengths than those in males.

Heel Part of the foot in the back

The heel is the prominence at the posterior end of the foot. It is based on the projection of one bone, the calcaneus or heel bone, behind the articulation of the bones of the lower leg.

Tendinopathy Medical condition

Tendinopathy, a type of tendon disorder that results in pain, swelling, and impaired function. The pain is typically worse with movement. It most commonly occurs around the shoulder, elbow, wrist, hip, knee, or ankle.

Achilles heel Critical weakness which can lead to downfall in spite of overall strength

An Achilles' heel is a weakness in spite of overall strength, which can lead to downfall. While the mythological origin refers to a physical vulnerability, idiomatic references to other attributes or qualities that can lead to downfall are common.

Calcaneus 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.

Plantar fascia Aponeurosis of the sole of the foot

The plantar fascia is the thick connective tissue (aponeurosis) which supports the arch on the bottom of the foot. It runs from the tuberosity of the calcaneus forward to the heads of the metatarsal bones.

Plantar fasciitis Connective tissue disorder of the heel

Plantar fasciitis 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 first steps of the day or following a period of rest. Pain is also frequently brought on by bending the foot and toes up towards the shin. The pain typically comes on gradually, and it affects both feet in about one-third of cases.

Achilles tendinitis Medical condition of the ankle and heel

Achilles tendinitis, also known as achilles tendinopathy, occurs when the Achilles tendon, found at the back of the ankle, becomes sore. Achilles tendinopathy is accompanied by alterations in the tendon's structure and mechanical properties. The most common symptoms are pain and swelling around the affected tendon. The pain is typically worse at the start of exercise and decreases thereafter. Stiffness of the ankle may also be present. Onset is generally gradual.

Achilles tendon rupture Medical condition were the tendon at the back of the ankle breaks

Achilles tendon rupture is when the Achilles tendon, at the back of the ankle, breaks. Symptoms include the sudden onset of sharp pain in the heel. A snapping sound may be heard as the tendon breaks and walking becomes difficult.

Soleus muscle Powerful muscle in the back part of the lower leg

In humans and some other mammals, the soleus is a powerful muscle in the back part of the lower leg. It runs from just below the knee to the heel, and is involved in standing and walking. It is closely connected to the gastrocnemius muscle and some anatomists consider them to be a single muscle, the triceps surae. Its name is derived from the Latin word "solea", meaning "sandal".

Triceps surae muscle Pair of muscles: gastrocnemius and the soleus

The triceps surae consists of two muscles located at the calf – the two-headed gastrocnemius and the soleus. These muscles both insert into the calcaneus, the bone of the heel of the human foot, and form the major part of the muscle of the posterior leg, commonly known as the calf muscle.

Gastrocnemius muscle Calf muscle

The gastrocnemius muscle is a superficial two-headed muscle that is in the back part of the lower leg of humans. It runs from its two heads just above the knee to the heel, a three joint muscle. The muscle is named via Latin, from Greek γαστήρ (gaster) 'belly' or 'stomach' and κνήμη (knḗmē) 'leg', meaning 'stomach of the leg'.

Plantaris muscle One of the superficial muscles of the superficial posterior compartment of the leg,

The plantaris is one of the superficial muscles of the superficial posterior compartment of the leg, one of the fascial compartments of the leg.

Calcaneal spur Medical condition of the heel

A calcaneal spur is a bony outgrowth from the calcaneal tuberosity. Calcaneal spurs are typically detected by x-ray examination. It is a form of exostosis.

Enthesitis Medical condition

Enthesitis is inflammation of the entheses, the sites where tendons or ligaments insert into the bone. It is an enthesopathy, a pathologic condition of the entheses. Early clinical manifestations are an aching sensation akin to "working out too much", and it gets better with activity. It is worse in the morning. The muscle insertion hurts very focally as it joins into the bone, but there is little to no pain at all with passive motion. There are some cases of isolated, primary enthesitis which are very poorly studied and understood. It is known to be associated with other autoimmune diseases, like spondyloarthropathies and psoriasis. A common autoimmune enthesitis is at the heel, where the Achilles tendon attaches to the calcaneus.

Calcaneal fracture Medical condition

A calcaneal fracture is a break of the calcaneus. Symptoms may include pain, bruising, trouble walking, and deformity of the heel. It may be associated with breaks of the hip or back.

Calf (leg) Back part of lower leg

The calf is the back portion of the lower leg in human anatomy. The muscles within the calf correspond to the posterior compartment of the leg. The two largest muscles within this compartment are known together as the calf muscle and attach to the heel via the Achilles tendon. Several other, smaller muscles attach to the knee, the ankle, and via long tendons to the toes.

In humans, the accessory soleus muscle is the most common accessory muscle in the ankle. It is often asymptomatic.

Ankle problems Medical condition

Ankle problems are of frequent occurrence and feature symptoms which include pain or discomfort experienced in the ankles.

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