The sciatic nerve, also called the ischiadic nerve, is a large nerve 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 verte ...

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 ex ...

. It is the longest and widest single nerve in the human body, 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 nerves L4 to S3. It contains fibers from both the anterior and posterior divisions of the

lumbosacral plexus The anterior divisions of the lumbar nerves, sacral 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 ...

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 sp ...

. 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 ins ...

. 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 sci ...

, quitting the pelvis. 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 t ...

, 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 and lateral compartments of the leg into the foot The sciatic nerve is the largest nerve in the human body. 3D still showing Sciatica nerve

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 animal coverings, such as the arthropod exoskeleton, have different de ...

of the foot, 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

, and the lower leg and upper surface of the foot via the

. The sciatic nerve also innervates muscles. In particular: * Via the

, the muscles in the

and sole of the foot (plantar aspect). * Via the

, the muscles in the anterior 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 ph ...

ing, muscular hypertension, 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 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 i ...

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 inse ...

in a

minimally invasive Minimally invasive procedures (also known as minimally invasive surgeries) encompass Surgery, surgical techniques that limit the size of incisions needed, thereby reducing wound healing time, associated pain, and risk of infection. Surgery by d ...

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,

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. Quadratu ...

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 quadrupe ...

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, 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 inclu ...

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.

Notes

References

External links

* * * () * ()
Sciatica and the Sciatic Nerve
{{Authority control Nerves of the lower limb and lower torso