The Achilles tendon or heel cord, also known as the calcaneal tendon, is a
tendon
A tendon or sinew is a tough band of fibrous connective tissue, dense fibrous connective tissue that connects skeletal muscle, muscle to bone. It sends the mechanical forces of muscle contraction to the skeletal system, while withstanding tensi ...
at the back of the lower
leg
A leg is a weight-bearing and locomotive anatomical structure, usually having a columnar shape. During locomotion, legs function as "extensible struts". The combination of movements at all joints can be modeled as a single, linear element cap ...
, and is the thickest in the human body.
It serves to attach the
plantaris,
gastrocnemius
The gastrocnemius muscle (plural ''gastrocnemii'') is a superficial two-headed muscle that is in the back part of the lower leg of humans. It is located superficial to the soleus in the posterior (back) compartment of the leg. It runs from its t ...
(calf) and
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 ...
s to 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. These muscles, acting via the tendon, cause
plantar flexion
Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relativ ...
of the foot at the
ankle joint
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. Th ...
, and (except the soleus)
flexion
Motion, the process of movement, is described using specific anatomical terminology, anatomical terms. Motion includes movement of Organ (anatomy), organs, joints, Limb (anatomy), limbs, and specific sections of the body. The terminology used de ...
at the
knee
In humans and other primates, the knee joins the thigh with the leg and consists of two joints: one between the femur and tibia (tibiofemoral joint), and one between the femur and patella (patellofemoral joint). It is the largest joint in the hu ...
.
Abnormalities of the Achilles tendon include inflammation (
Achilles tendinitis
Achilles tendinitis, also known as Achilles tendinopathy, is soreness of the Achilles tendon. It is accompanied by alterations in the tendon's structure and mechanical properties. The most common symptoms are pain and swelling around the back of ...
), degeneration,
rupture, and becoming embedded with cholesterol deposits (
xanthoma
A xanthoma (pl. xanthomas or xanthomata) (condition: xanthomatosis) is a deposition of yellowish cholesterol-rich material that can appear anywhere in the body in various disease states. They are cutaneous manifestations of lipidosis in which lip ...
s).
The Achilles tendon was named in 1693 after the Greek hero
Achilles
In Greek mythology, Achilles ( ) or Achilleus () was a hero of the Trojan War who was known as being the greatest of all the Greek warriors. The central character in Homer's ''Iliad'', he was the son of the Nereids, Nereid Thetis and Peleus, ...
.
History
The oldest-known written record of the tendon being named after
Achilles
In Greek mythology, Achilles ( ) or Achilleus () was a hero of the Trojan War who was known as being the greatest of all the Greek warriors. The central character in Homer's ''Iliad'', he was the son of the Nereids, Nereid Thetis and Peleus, ...
is in 1693 by the Flemish/Dutch anatomist
Philip Verheyen. In his widely used text he described the tendon's location and said that it was commonly called "the cord of Achilles."
The tendon has been described as early as the time of
Hippocrates
Hippocrates of Kos (; ; ), also known as Hippocrates II, was a Greek physician and philosopher of the Classical Greece, classical period who is considered one of the most outstanding figures in the history of medicine. He is traditionally referr ...
, who described it as the "" (Latin for "great tendon") and by subsequent anatomists prior to Verheyen as "" (Latin for "Hippocrates' string").
[
Verheyen referred to the mythological account of Achilles being held by the heel by his mother ]Thetis
Thetis ( , or ; ) is a figure from Greek mythology with varying mythological roles. She mainly appears as a sea nymph, a goddess of water, and one of the 50 Nereids, daughters of the ancient sea god Nereus.
When described as a Nereid in Cl ...
when she dipped him in the River Styx
In Greek mythology, Styx (; ; lit. "Shuddering"), also called the River Styx, is a goddess and one of the rivers of the Greek Underworld. Her parents were the Titans Oceanus and Tethys, and she was the wife of the Titan Pallas and the mothe ...
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
An Achilles' heel (or Achilles heel) is a weakness despite 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 do ...
") 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.[ The first closed rupture was described by Ambroise Pare in the sixteenth century.][
The Achilles tendon is also known as the "" (Latin for "calcaneal tendon").][ Because ]eponyms
An eponym is a noun after which or for which someone or something is, or is believed to be, named. Adjectives derived from the word ''eponym'' include ''eponymous'' and ''eponymic''.
Eponyms are commonly used for time periods, places, innovati ...
(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 , meaning heel.
Structure
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
The gastrocnemius muscle (plural ''gastrocnemii'') is a superficial two-headed muscle that is in the back part of the lower leg of humans. It is located superficial to the soleus in the posterior (back) compartment of the leg. It runs from its t ...
and soleus
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 ...
muscles to the calcaneal tuberosity on 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). 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 above its insertion.
The tendon is covered by the 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.
...
and skin, and stands out prominently behind the bone; the gap is filled up with areolar and adipose tissue
Adipose tissue (also known as body fat or simply fat) is a loose connective tissue composed mostly of adipocytes. It also contains the stromal vascular fraction (SVF) of cells including preadipocytes, fibroblasts, Blood vessel, vascular endothel ...
. A bursa
Bursa () is a city in northwestern Turkey and the administrative center of Bursa Province. The fourth-most populous city in Turkey and second-most populous in the Marmara Region, Bursa is one of the industrial centers of the country. Most of ...
lies between the tendon and the upper part of the calcaneus. It is about long.
Along the side of the muscle, and superficial to it, is the small saphenous vein
The small saphenous vein (also short saphenous vein or lesser saphenous vein) is a relatively large superficial vein of the posterior leg.
Structure
The origin of the small saphenous vein (SSV) is where the dorsal vein from the fifth digit (smal ...
. The sural nerve
The sural nerve ''(L4-S1)'' is generally considered a pure cutaneous nerve of the posterolateral leg to the lateral ankle. The sural nerve originates from a combination of either the sural communicating branch and medial sural cutaneous 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. The tendon is the thickest tendon in the human body. It can receive a load stress 3.9 times body weight during walking and 7.7 times body weight when running.
The blood supply to the Achilles tendon is poor, and mostly via a recurrent branch of the posterior tibial artery
The posterior tibial artery of the lower limb is an artery that carries blood to the posterior compartment of the leg and plantar surface of the foot. It branches from the popliteal artery via the tibial-fibular trunk.
Structure
The posteri ...
, and some through arterial branches passing through surrounding muscles.
Function
Acting via the Achilles tendon, the gastrocnemius and soleus muscles cause plantar flexion
Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relativ ...
of the foot at the ankle
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 ...
. 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
The tibial nerve is a branch of the sciatic nerve. The tibial nerve passes through the popliteal fossa to pass below the arch of soleus.
Structure Popliteal fossa
The tibial nerve is the larger terminal branch of the sciatic nerve with root val ...
. 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.
Vibration of the tendon without vision has a major impact on postural orientation. Vibration of the tendon causes movement backwards and the illusion of a forward body tilt in standing subjects. This is because vibrations stimulate muscle spindle
Muscle spindles are stretch receptors within the body of a skeletal muscle that primarily detect changes in the length of the muscle. They convey length information to the central nervous system via afferent nerve fibers. This information can be ...
s in the calf muscles. The muscle spindles alert the brain that the body is moving forward, so the central nervous system
The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain, spinal cord and retina. The CNS is so named because the brain integrates the received information and coordinates and influences the activity o ...
compensates by moving the body backwards.
Clinical significance
Inflammation
Inflammation
Inflammation (from ) is part of the biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. The five cardinal signs are heat, pain, redness, swelling, and loss of function (Latin ''calor'', '' ...
of the Achilles tendon is called Achilles tendinitis
Achilles tendinitis, also known as Achilles tendinopathy, is soreness of the Achilles tendon. It is accompanied by alterations in the tendon's structure and mechanical properties. The most common symptoms are pain and swelling around the back of ...
. Achilles tendinosis is the soreness or stiffness of the tendon, particularly worse when exercising, and generally due to overuse. The most common symptoms are sharp achy 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.[
It commonly occurs as a result of overuse such as ]running
Running is a method of terrestrial locomotion by which humans and other animals move quickly on foot. Running is a gait with an aerial phase in which all feet are above the ground (though there are exceptions). This is in contrast to walkin ...
. Other risk factors include trauma, a lifestyle that includes little exercise, high-heel shoes, rheumatoid arthritis
Rheumatoid arthritis (RA) is a long-term autoimmune disorder that primarily affects synovial joint, joints. It typically results in warm, swollen, and painful joints. Pain and stiffness often worsen following rest. Most commonly, the wrist and h ...
, and medications of the fluoroquinolone
Quinolone antibiotics constitute a large group of broad-spectrum bacteriocidals that share a bicyclic core structure related to the substance 4-quinolone. They are used in human and veterinary medicine to treat bacterial infections, as well ...
or steroid
A steroid is an organic compound with four fused compound, fused rings (designated A, B, C, and D) arranged in a specific molecular configuration.
Steroids have two principal biological functions: as important components of cell membranes t ...
class.[ Diagnosis is generally based on symptoms and examination.][
While ]stretching
Stretching is a form of physical exercise in which a specific muscle or tendon (or muscle group) is deliberately expanded and flexed in order to improve the muscle's felt elasticity and achieve comfortable muscle tone. The result is a feelin ...
and exercises to strengthen the back are often recommended for prevention, evidence to support these measures is poor. Treatment typically involves rest, ice, non-steroidal antiinflammatory agents
Non-steroidal anti-inflammatory drugs (NSAID) are members of a therapeutic drug class which reduces pain, decreases inflammation, decreases fever, and prevents blood clots. Side effects depend on the specific drug, its dose and duration of ...
(NSAIDs), and physical therapy
Physical therapy (PT), also known as physiotherapy, is a healthcare profession, as well as the care provided by physical therapists who promote, maintain, or restore health through patient education, physical intervention, disease preventio ...
.[ A heel lift or ]orthotic
Orthotics () is a medical specialty that focuses on the design and application of orthoses, sometimes known as braces, calipers, or splints. An is "an externally applied device used to influence the structural and functional characteristics of ...
s may also be helpful.[ In those in whose symptoms last more than six months despite other treatments, surgery may be considered.] Achilles tendinitis is relatively common.
Degeneration
Achilles tendon degeneration (tendinosis) is typically investigated with either MRI
Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to generate pictures of the anatomy and the physiological processes inside the body. MRI scanners use strong magnetic fields, magnetic field gradients, and rad ...
or ultrasound
Ultrasound is sound with frequency, frequencies greater than 20 Hertz, kilohertz. This frequency is the approximate upper audible hearing range, limit of human hearing in healthy young adults. The physical principles of acoustic waves apply ...
. In both cases, the tendon is thickened, may demonstrate surrounding inflammation by virtue of the presence of paratenonitis, retrocalcaneal or retro-achilles bursitis
Bursitis is the inflammation of one or more bursae (synovial sacs) of synovial fluid in the body. They are lined with a synovial membrane that secretes a lubricating synovial fluid. There are more than 150 bursae in the human body. The bursae (bu ...
. 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
An enthesopathy refers to a disorder involving the attachment of a tendon or ligament to a bone. This site of attachment is known as the entheses, enthesis (pl. entheses).
If the condition is known to be Inflammation, inflammatory, it can more pr ...
may be seen in the context of advancing age, it is also associated with arthritis
Arthritis is a general medical term used to describe a disorder that affects joints. Symptoms generally include joint pain and stiffness. Other symptoms may include redness, warmth, Joint effusion, swelling, and decreased range of motion of ...
such as gout
Gout ( ) is a form of inflammatory arthritis characterized by recurrent attacks of pain in a red, tender, hot, and Joint effusion, swollen joint, caused by the deposition of needle-like crystals of uric acid known as monosodium urate crysta ...
and the seronegative spondyloarthritides. Achilles tendinosis is a known risk factor for calf muscle tears.
Rupture
Achilles tendon rupture is when the Achilles tendon breaks.[ Symptoms include the sudden onset of sharp pain in the ]heel
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.
Structure
To distribute the compressive forces exerted ...
. A snapping sound may be heard as the tendon breaks and walking becomes difficult.
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.[ Other risk factors include the use of ]fluoroquinolones
Quinolone antibiotics constitute a large group of broad-spectrum antibiotic, broad-spectrum bacteriocidals that share a bicyclic molecule, bicyclic core structure related to the substance 4-Quinolone, 4-quinolone. They are used in human and ve ...
, a significant change in exercise, rheumatoid arthritis
Rheumatoid arthritis (RA) is a long-term autoimmune disorder that primarily affects synovial joint, joints. It typically results in warm, swollen, and painful joints. Pain and stiffness often worsen following rest. Most commonly, the wrist and h ...
, gout
Gout ( ) is a form of inflammatory arthritis characterized by recurrent attacks of pain in a red, tender, hot, and Joint effusion, swollen joint, caused by the deposition of needle-like crystals of uric acid known as monosodium urate crysta ...
, or corticosteroid
Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex of vertebrates, as well as the synthetic analogues of these hormones. Two main classes of corticosteroids, glucocorticoids and mineralocorticoids, are invo ...
use.[ Diagnosis is typically based on symptoms and examination and supported by ]medical imaging
Medical imaging is the technique and process of imaging the interior of a body for clinical analysis and medical intervention, as well as visual representation of the function of some organs or tissues (physiology). Medical imaging seeks to revea ...
.[ Achilles tendon rupture occurs in about 1 per 10,000 people per year.] Males are more commonly affected than females.[ People in their 30s to 50s are most commonly affected.][
Prevention may include stretching before activity.][ Treatment may be by surgery or ]casting
Casting is a manufacturing process in which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a casting, which is ejected or ...
with the toes somewhat pointed down.[ Relatively rapid return to weight bearing (within 4 weeks) appears acceptable.][ The risk of re-rupture is about 25% with casting.][ If appropriate treatment does not occur within 4 weeks of the injury outcomes suffer.
]
Xanthomas
Tendon xanthomas are cholesterol deposits that commonly develop in the Achilles tendon of people with lipid metabolism disorders such as familial hypercholesterolemia
Familial hypercholesterolemia (FH) is a genetic disorder characterized by high cholesterol levels, specifically very high levels of low-density lipoprotein cholesterol (LDL cholesterol), in the blood and early cardiovascular diseases. The mos ...
.
Neurological exam
The Achilles tendon is often tested as part of a neurological examination
A neurological examination is the assessment of sensory neuron and motor responses, especially reflexes, to determine whether the nervous system is impaired. This typically includes a physical examination and a review of the patient's medical his ...
. In this examination, the tendon is hit with a tendon hammer. This tests the S1 and S2 spinal nerve
A spinal nerve is a mixed nerve, which carries Motor neuron, motor, Sensory neuron, sensory, and Autonomic nervous system, autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each s ...
s: a normal response is plantar flexion
Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relativ ...
(downward movement) of the foot.
Level or portion of tendon affected:
* Paratendinopathy: The inflammation of a connective tissue sleeve which surrounds the tendon and protects it from friction, irritation, and repeated trauma
* Insertional: Eminently overuse-injury which frequently occurs in running and jumping athletes. Patients affected by insertional Achilles tendinopathy complain of pain on the posterior aspect of the heel and may have morning stiffness, swelling with activity and tenderness at the tendon insertion level. If this condition becomes chronic, calcific deposits at the Achilles insertional level may be developed (due to microfractures and healing of the osteotendinous union) which can degenerate, if it persists over time, in the abnormal bony prominence on the posterior aspect of heel, condition known as Haglund deformity, which can be painful and difficult close-shoes fitting due to friction and irritation.
* Mid-portion: Occurs approximately 2–7 cm proximal from the Achilles insertion into the calcaneus. Characterized by a combination of pain and swelling at this level. It has associated a remarkable impaired performance.
Other animals
The Achilles tendon is short or absent in great ape
The Hominidae (), whose members are known as the great apes or hominids (), are a taxonomic family of primates that includes eight extant species in four genera: '' Pongo'' (the Bornean, Sumatran and Tapanuli orangutan); '' Gorilla'' (the ...
s, but long in arboreal gibbon
Gibbons () are apes in the family Hylobatidae (). The family historically contained one genus, but now is split into four extant genera and 20 species. Gibbons live in subtropical and tropical forests from eastern Bangladesh and Northeast Indi ...
s and humans. It provides elastic energy storage in hopping, walking, and running. Computer models suggest this energy storage Achilles tendon increases top running speed by >80% and reduces running costs by more than 75%. 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."
See also
* Heel lifts
References
External links
*
{{Use dmy dates, date=April 2017
Human anatomy
Tendons
Lower limb anatomy
Achilles
Words and phrases derived from Greek mythology