The sciatic nerve, also called the ischiadic nerve, is a large
nerve
A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system.
A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...
in humans and other vertebrate animals which is the largest branch of the
sacral plexus
In human anatomy, the sacral plexus is a nerve plexus which provides motor and sensory nerves for the posterior thigh, most of the lower leg and foot, and part of the pelvis. It is part of the lumbosacral plexus and emerges from the lumbar vertebr ...
and runs alongside the hip joint and down the
lower limb
The human leg, in the general word sense, is the entire lower limb of the human body, including the foot, thigh or sometimes even the hip or gluteal region. However, the definition in human anatomy refers only to the section of the lower limb ext ...
. It is the longest and widest single nerve in the
human body
The human body is the structure of a Human, human being. It is composed of many different types of Cell (biology), cells that together create Tissue (biology), tissues and subsequently organ systems. They ensure homeostasis and the life, viabi ...
, going from the top of the leg to the foot on the posterior aspect. The sciatic nerve has no cutaneous branches for the thigh. This nerve provides the connection to the nervous system for the skin of the lateral leg and the whole foot, the muscles of the back of the thigh, and those of the leg and foot. It is derived from
spinal nerve
A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each side of the vertebral column. These are grouped into th ...
s
L4 to
S3. It contains
fibers
Fiber or fibre (from la, fibra, links=no) is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often incorporate ...
from both the anterior and posterior divisions of the
lumbosacral plexus
The anterior divisions of the lumbar nerves, sacral nerves, and coccygeal nerve form the lumbosacral plexus, the first lumbar nerve being frequently joined by a branch from the twelfth thoracic. For descriptive purposes this plexus is usually divi ...
.
Structure
In humans, the sciatic nerve is formed from the L4 to S3 segments of the sacral plexus, a collection of nerve fibres that emerge from the
sacral
Sacral may refer to:
*Sacred
Sacred describes something that is dedicated or set apart for the service or worship of a deity; is considered worthy of spiritual respect or devotion; or inspires awe or reverence among believers. The property ...
part of the
spinal cord
The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the spi ...
. The lumbosacral trunk from the L4 and L5 roots descends between the sacral promontory and ala and the S1 to S3 roots emerge from the ventral sacral foramina. These nerve roots unite to form a single nerve in front of the
piriformis muscle
The piriformis muscle () is a flat, pyramidally-shaped muscle in the gluteal region of the lower limbs. It is one of the six muscles in the lateral rotator group.
The piriformis muscle has its origin upon the front surface of the sacrum, and inse ...
. The nerve passes beneath
piriformis
The piriformis muscle () is a flat, pyramidally-shaped muscle in the gluteal region of the lower limbs. It is one of the six muscles in the lateral rotator group.
The piriformis muscle has its origin upon the front surface of the sacrum, and in ...
and through the
greater sciatic foramen
The greater sciatic foramen is an opening (foramen) in the posterior human pelvis. It is formed by the sacrotuberous and sacrospinous ligaments. The piriformis muscle passes through the foramen and occupies most of its volume. The greater sciati ...
, quitting the
pelvis
The pelvis (plural pelves or pelvises) is the lower part of the trunk, between the abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also called bony pelvis, or pelvic skeleton).
The ...
.
From here, it travels down the posterior thigh to the
popliteal fossa
The popliteal fossa (also referred to as hough, .html" ;"title="/sup>">/sup> or kneepit in analogy to the cubital fossa) is a shallow depression located at the back of the knee joint. The bones of the popliteal fossa are the femur and the tibia ...
. The nerve travels in the
posterior compartment of the thigh behind (superficial to) the
adductor magnus muscle Adductor may refer to:
* One of the anatomical terms of motion
* Adductor muscle (disambiguation)
* Adductor canal
The adductor canal, also known as the subsartorial canal or Hunter’s canal, is an aponeurotic tunnel in the middle third of the th ...
, and is itself in front of (deep to) the long head of the
biceps femoris muscle
The biceps femoris () is a muscle of the thigh located to the posterior, or back. As its name implies, it has two parts, one of which (the long head) forms part of the hamstrings muscle group.
Structure
It has two heads of origin:
*the ''long h ...
. At the popliteal fossa, the nerve divides into its two branches:
* 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 ...
, which travels down the
posterior compartment of the leg
The posterior compartment of the leg is one of the fascial compartments of the leg and is divided further into deep and superficial compartments.
Structure Muscles Superficial posterior compartment
Deep posterior compartment
Blood ...
into the foot
* The
common fibular nerve
The common fibular nerve (also known as the common peroneal nerve, external popliteal nerve, or lateral popliteal nerve) is a nerve in the lower leg that provides sensation over the posterolateral part of the leg and the knee joint. It divides at ...
(also called the
common peroneal nerve
The common fibular nerve (also known as the common peroneal nerve, external popliteal nerve, or lateral popliteal nerve) is a nerve in the lower leg that provides sensation over the posterolateral part of the leg and the knee joint. It divides at ...
), which travels down the
anterior
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...
and
lateral compartments of the leg into the foot
The sciatic nerve is the largest nerve in the human body.
Development
Function
The sciatic nerve supplies sensation to the
skin
Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation.
Other cuticle, animal coverings, such as the arthropod exoskeleton, have diffe ...
of the
foot
The foot ( : feet) 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 ...
, as well as the entire lower leg (except for its inner side). Sensation to skin to the sole of the foot is provided 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 ...
, and the lower leg and upper surface of the foot via the
common fibular nerve
The common fibular nerve (also known as the common peroneal nerve, external popliteal nerve, or lateral popliteal nerve) is a nerve in the lower leg that provides sensation over the posterolateral part of the leg and the knee joint. It divides at ...
.
The sciatic nerve also innervates muscles. In particular:
* Via 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 ...
, the muscles in the
posterior compartment of the leg
The posterior compartment of the leg is one of the fascial compartments of the leg and is divided further into deep and superficial compartments.
Structure Muscles Superficial posterior compartment
Deep posterior compartment
Blood ...
and sole of the foot (plantar aspect).
* Via the
common fibular nerve
The common fibular nerve (also known as the common peroneal nerve, external popliteal nerve, or lateral popliteal nerve) is a nerve in the lower leg that provides sensation over the posterolateral part of the leg and the knee joint. It divides at ...
, the muscles in the
anterior
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...
and
lateral compartments of the leg.
Clinical significance
Sciatica
Pain caused by a compression or irritation of the sciatic nerve by a problem in the lower back is called
sciatica
Sciatica is pain going down the leg from the lower back. This pain may go down the back, outside, or front of the leg. Onset is often sudden following activities like heavy lifting, though gradual onset may also occur. The pain is often described ...
. Common causes of sciatica include the following lower back and hip conditions:
spinal disc herniation
Spinal disc herniation is an injury to the cushioning and connective tissue between vertebrae, usually caused by excessive strain or trauma to the spine. It may result in back pain, pain or sensation in different parts of the body, and physical ...
,
degenerative disc disease
Degenerative disc disease (DDD) is a medical condition typically brought on by the normal aging process in which there are anatomic changes and possibly a loss of function of one or more intervertebral discs of the spine. DDD can take place with ...
,
lumbar spinal stenosis
Lumbar spinal stenosis (LSS) is a medical condition in which the spinal canal narrows and compresses the nerves and blood vessels at the level of the lumbar vertebrae. Spinal stenosis may also affect the cervical or thoracic region, in which case ...
,
spondylolisthesis
Spondylolisthesis is the displacement of one spinal vertebra compared to another. While some medical dictionaries define spondylolisthesis specifically as the forward or anterior displacement of a vertebra over the vertebra inferior to it (or t ...
, and
piriformis syndrome
Piriformis syndrome is a condition which is believed to result from compression of the sciatic nerve by the piriformis muscle. Symptoms may include pain and numbness in the buttocks and down the leg. Often symptoms are worsened with sitting or ru ...
. Other acute causes of sciatica include
cough
A cough is a sudden expulsion of air through the large breathing passages that can help clear them of fluids, irritants, foreign particles and microbes. As a protective reflex, coughing can be repetitive with the cough reflex following three pha ...
ing, muscular
hypertension
Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high bl ...
, and
sneezing
A sneeze (also known as sternutation) is a semi-autonomous, convulsive expulsion of air from the lungs through the nose and mouth, usually caused by foreign particles irritating the nasal mucosa. A sneeze expels air forcibly from the mouth and ...
.
Injury
Sciatic nerve injury occurs between 0.5% and 2.0% of the time during a
hip replacement
Hip replacement is a surgical procedure in which the hip joint is replaced by a prosthetic implant, that is, a hip prosthesis. Hip replacement surgery can be performed as a total replacement or a hemi (half) replacement. Such joint replacement o ...
.
Sciatic nerve palsy is a complication of total hip arthroplasty with an incidence of 0.2% to 2.8% of the time, or with an incidence of 1.7% to 7.6% following revision. Following the procedure, in rare cases, a screw, broken piece of trochanteric wire, fragment of
methyl methacrylate
Methyl methacrylate (MMA) is an organic compound with the formula CH2=C(CH3)COOCH3. This colorless liquid, the methyl ester of methacrylic acid (MAA), is a monomer produced on a large scale for the production of poly(methyl methacrylate) (PMMA ...
bone cement, or of a
Burch-Schneider antiprofusio cage can impinge on the nerve; this can cause sciatic nerve
palsy Palsy is a medical term which refers to various types of paralysisDan Agin, ''More Than Genes: What Science Can Tell Us About Toxic Chemicals, Development, and the Risk to Our Children;; (2009), p. 172. or paresis, often accompanied by weakness a ...
which may resolve after the fragment is removed and the nerve freed. The nerve can be surrounded in oxidized regenerated cellulose to prevent further scarring. Sciatic nerve palsy can also result from severe
spinal stenosis
Spinal stenosis is an abnormal narrowing of the spinal canal or neural foramen that results in pressure on the spinal cord or nerve roots. Symptoms may include pain, numbness, or weakness in the arms or legs. Symptoms are typically gradual in on ...
following the procedure, which can be addressed by
spinal decompression
Spinal decompression is the relief of pressure on the spinal cord or on one or more compressed nerve roots passing through or exiting the spinal column. Decompression of the spinal neural elements is a key component in treating spinal radiculopath ...
surgery.
It is unclear if
inversion therapy
Inversion therapy, or simply inversion, is the process of seeking therapeutic benefits from hanging by the legs, ankles, or feet in an inverted angle or entirely upside down. It is a form of spinal traction. Spinal Traction can be useful for eff ...
is able to decompress the sacral vertebrae; it may only work on the lumbar aspects of the sciatic nerves.
Sciatic nerve injury may also occur from improperly performed injections into the buttock, and may result in sensory loss.
Other disease
Bernese periacetabular
osteotomy
An osteotomy is a surgical operation whereby a bone is cut to shorten or lengthen it or to change its alignment. It is sometimes performed to correct a hallux valgus, or to straighten a bone that has healed crookedly following a fracture. It is ...
resulted in major nerve deficits in the sciatic or femoral nerves in 2.1% of 1760 patients, of whom approximately half experienced complete recovery within a mean of 5.5 months.
Sciatic nerve exploration can be done by
endoscopy
An endoscopy is a procedure used in medicine to look inside the body. The endoscopy procedure uses an endoscope to examine the interior of a hollow organ or cavity of the body. Unlike many other medical imaging techniques, endoscopes are insert ...
in a
minimally invasive
Minimally invasive procedures (also known as minimally invasive surgeries) encompass surgical techniques that limit the size of incisions needed, thereby reducing wound healing time, associated pain, and risk of infection. Surgery by definition ...
procedure to assess lesions of the nerve. Endoscopic treatment for sciatic nerve entrapment has been investigated in
deep gluteal syndrome. Patients were treated with sciatic nerve decompression by
resection of fibrovascular scar bands,
piriformis
The piriformis muscle () is a flat, pyramidally-shaped muscle in the gluteal region of the lower limbs. It is one of the six muscles in the lateral rotator group.
The piriformis muscle has its origin upon the front surface of the sacrum, and in ...
tendon release,
obturator internus
The internal obturator muscle or obturator internus muscle originates on the medial surface of the obturator membrane, the ischium near the membrane, and the rim of the pubis.
It exits the pelvic cavity through the lesser sciatic foramen.
The i ...
, or
quadratus femoris
The quadratus femoris is a flat, quadrilateral skeletal muscle. Located on the posterior side of the hip joint, it is a strong external rotator and adductor of the thigh, but also acts to stabilize the femoral head in the acetabulum. Quadratus ...
or by
hamstring
In human anatomy, a hamstring () is any one of the three posterior thigh muscles in between the hip and the knee (from medial to lateral: semimembranosus, semitendinosus and biceps femoris). The hamstrings are susceptible to injury.
In quadrupeds, ...
tendon scarring.
Anesthetic
Signals from the sciatic nerve and its branches can be blocked, in order to interrupt transmission of
pain signal from the innervation area, by performing a
regional nerve blockade called a
sciatic nerve block
A sciatic nerve block is a nerve block that uses local anesthetic to achieve analgesia in the leg. The block works by affecting the sciatic nerve and is used for surgeries at or below the knee.
The sciatic nerve is located in the gluteus maximus ...
.
Society and culture
According to
Jewish law
''Halakha'' (; he, הֲלָכָה, ), also Romanization of Hebrew, transliterated as ''halacha'', ''halakhah'', and ''halocho'' ( ), is the collective body of Judaism, Jewish religious laws which is derived from the Torah, written and Oral Tora ...
, the sciatic nerve (
Hebrew
Hebrew (; ; ) is a Northwest Semitic language of the Afroasiatic language family. Historically, it is one of the spoken languages of the Israelites and their longest-surviving descendants, the Jews and Samaritans. It was largely preserved ...
:
Gid hanasheh
''Gid Hanasheh'' ( he, גִּיד הַנָּשֶׁה ''Gīḏ hanNāše'', literally "forgotten sinew", often translated as "displaced tendon") is the term for sciatic nerve in Judaism. It may not be eaten by Jews according to Halacha (Jewish Law ...
) may not be eaten by Jews, to commemorate
Jacob
Jacob (; ; ar, يَعْقُوب, Yaʿqūb; gr, Ἰακώβ, Iakṓb), later given the name Israel, is regarded as a patriarch of the Israelites and is an important figure in Abrahamic religions, such as Judaism, Christianity, and Islam. J ...
's injury in his struggle with an
angel
In various theistic religious traditions an angel is a supernatural spiritual being who serves God.
Abrahamic religions often depict angels as benevolent celestial intermediaries between God (or Heaven) and humanity. Other roles include ...
.
Additional images
File:Sciatic nerve1.jpg, Sciatic nerve.
File:Gray344.png, Structures surrounding left hip-joint.
File:Gray832.png, Nerves of the right lower extremity. Posterior view.
File:Slide4i.JPG, Sciatic nerve.
File:Slide8z.JPG, Sciatic nerve.
File:Slide4hh.JPG, Sciatic nerve.
See also
*
Lesser sciatic notch
Below the ischial spine is a small notch, the lesser sciatic notch; it is smooth, coated in the recent state with cartilage, the surface of which presents two or three ridges corresponding to the subdivisions of the tendon of the Obturator internus ...
*
Greater sciatic notch
The greater sciatic notch is a notch in the ilium (bone), ilium, one of the bones that make up the human pelvis. It lies between the posterior inferior iliac spine (above), and the ischial spine (below). The sacrospinous ligament changes this notch ...
Notes
References
External links
*
*
* ()
* ()
Sciatica and the Sciatic Nerve
{{Authority control
Nerves of the lower limb and lower torso