Sciatic nerve anatomy


The sciatic nerves, located in the legs, are the largest nerves in the body. Each sciatic nerve stimulates movement of the leg muscles and transmits sensory signals from the leg to the spine. The right and left sciatic nerves, each of which controls, function on the ipsilateral (same) side of the body.

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Sciatic nerve pain, often called sciatica , is very common and has many causes. A herniated disc that pinches a nerve root is the most common of several causes of sciatica . Because the sciatic nerve provides sensation and movement, trauma or compression of the nerve can make you feel pain, numbness, and / or weakness. …


The sciatic nerve is a peripheral nerve. Its nerve roots emerge from the lower part of the spine and join to form the sciatic nerve. As the sciatic nerve travels down the leg, it divides into several smaller branches along the way.

Many of its branches provide nerve stimulation to the leg muscles. The sensory nerves in the leg and foot travel up the leg and fuse with the sciatic nerve.


The spinal cord, which is made up of nerve fibers, runs through the spinal column, also called the spinal column and spinal column. Nerve roots , also called spinal nerves, exit the spine at each level of the vertebrae through orifices (orifices).

The sciatic nerve is made up of five spinal nerves that connect to each other.

Two of these nerves, the L4 and L5 nerve roots, extend from the lower lumbar spine. Three other nerve roots, the S1, S2, and S3 nerve roots, extend from the sacral spine, which is the lowest part of the spine.

These nerve roots have fibers that originate in the ventral region (also called anterior or anterior) of the spine and the posterior region (also called dorsal or posterior) of the spine. The anterior fibers of the spine are responsible for motor function, while the posterior fibers of the spine are responsible for sensory function.

The sciatic nerve performs sensory and motor functions because the nerves in the front and back of the spine combine to form nerve roots that fuse with the sciatic nerve.

The sciatic nerve varies in width and diameter as it travels down the leg, with its greatest width at the junction of the five nerves before beginning to divide into its various branches as it travels down the leg.


The sciatic nerve passes through the foramen magnum, an opening formed by the bones of the pelvis. The nerve passes through the foramen magnum and runs along the back of the leg along the front of the piriformis muscle, which runs deep into the upper leg.

As the sciatic nerve travels down the upper leg (behind the thigh), several branches separate from the sciatic nerve, providing motor stimulation to the muscles in the upper leg.

As the sciatic nerve approaches the back of the knee, it divides into two main branches, the tibial nerve and the peroneal nerve. The tibial and peroneal nerves pass down the leg to the foot, dividing along the way into smaller motor and sensory branches. The tibial nerve is primarily the motor nerve and the peroneal nerve is primarily the sensory nerve.


The sciatic nerve controls most of the movement and sensation in the leg and foot.

The motor branches of the sciatic nerve receive messages from the anterior fibers of the spine and the dorsal roots. They run up the leg, with smaller nerve branches extending to the lower leg and foot muscles along the entire length of the nerve.

The feeling is defined by small sensory nerves located in the feet and legs. These nerves fuse as they travel down the sciatic nerve to the spinal nerve roots before entering the posterior fibers of the spinal cord, eventually sending sensory signals to the brain.


The motor branches of the sciatic nerve stimulate the calf muscles. These motor nerves stimulate various movements, including hip extension, knee flexion, and foot and toe flexion.

Muscles stimulated by the sciatic nerve in the thigh include:

  • Semitendinosus muscle
  • Semimembranosus muscle
  • Short head of the biceps femoris
  • Long head of the biceps femoris
  • Adductor magnus (often described as hamstring)

Branches of the tibial sciatic nerve stimulate the muscles of the lower leg, including:

  • Lateral and medial gastrocnemius muscle
  • Soleus
  • Long finger flexor
  • Popliteal
  • Posterior tibial muscle
  • Long flexor of the big toe

In the foot, the tibial nerve branches into the lateral plantar nerve, the medial plantar nerve, the lateral dorsal cutaneous nerve, the lateral calcaneal and medial calcaneal branches, and the plantar digital nerves, which stimulate movement of the foot muscles.


The sensory nerves in the leg carry messages of light touch, temperature, pain, positional sensation, and vibration. These small nerves fuse with the main branch of the sciatic nerve as they travel up the leg.

The branches of the sciatic nerve control the sensation of the entire foot and most of the leg below the knee.

The sensory branches of the sciatic nerve include:

  • Suural nerve : detects sensations in the back of the leg and in the lateral areas (towards the little finger) of the foot and fuses with the peroneal and tibial nerves.
  • Deep peroneal nerve: Detects tenderness on the lateral side of the lower leg and fuses with the peroneal nerve.
  • Superficial peroneal nerve : senses sensation on the lateral side of the leg just above the foot and the back of the foot and fuses with the peroneal nerve.
  • Branches of the medial calcaneus – finds sensation in the heel of the foot and fuses with the tibial nerve.

Related conditions

Several conditions can affect the sciatic nerve, causing pain, weakness and / or numbness of the entire area supplied by the nerve or one or more of its branches.

Disc herniation

The spinal column is a column of bones with cartilaginous discs in the middle. When the disc is herniated (displaced), it can compress the root of the sciatic nerve. This can cause symptoms of sciatic nerve dysfunction such as pain, weakness, or numbness in the areas of the foot and lower leg that are supplied by the sciatic nerve.

A herniated disc can be repaired with surgery , and sometimes therapy can relieve pressure on the nerve. Other treatments include anti-inflammatory drugs and injections or steroids or pain relievers near the affected area .

Vertebral foramen disease

Problems such as arthritis, inflammation, and bone destruction can affect the size and shape of the opening through which the spinal roots pass, resulting in compression of the nerve root (pinched nerve), resulting in lead to symptoms of sciatic nerve dysfunction or pain. Some women experience symptoms of a pinched nerve during pregnancy, and they usually go away after the baby is born .

Treatment includes rest, anti-inflammatories, and therapy.

Nerve injury

The sciatic nerve or its roots or branches can be damaged due to trauma. In some cases, nerve damage can occur during surgery, especially if there is a serious condition in the pelvis, such as cancer. Injury to the distal (lower) branches of the nerve can cause the foot to sag, resulting in a "hit" to the leg when walking.


Nervous disorders can occur due to chronic alcohol use, vitamin deficiencies , medications, or an inflammatory condition. This type of disease is described as neuropathy and can affect nerves throughout the body. Neuropathy usually begins distally (on the tips of the fingers and toes) and can begin in many areas of the body before spreading.

Neuropathy often causes symptoms such as pain, tingling, or burning. As the disease worsens and progresses, it causes numbness. Posterior neuropathy can also cause weakness .

Muscle spasms

If a muscle suddenly spasms (contracts involuntarily), it can put pressure on nearby nerves and cause symptoms. As the sciatic nerve travels through the piriformis muscle, spasms of that muscle can cause symptoms of sciatica. Muscle spasms generally do not damage the nerve. Symptoms should go away as soon as the muscle relaxes, either on its own or with the help of muscle relaxants.


The sciatic nerve may be infiltrated or compressed by a tumor, cancer, or metastatic cancer from other parts of the body. These growths can be removed with surgery or treated with chemotherapy or radiation.


Pelvic infection can affect the sciatic nerve. Meningitis, an infection of the fluid and mucous membrane that surrounds the spine and brain, can also cause inflammation and disease in or near the sciatic nerve. Infections that are treated with antimicrobial drugs, such as antibiotics, may get better before they cause permanent nerve damage.


A pinched nerve or herniated disc is a common condition, while other conditions associated with the sciatic nerve, such as cancer and infections, are less common.

Physical therapy is an effective treatment for mild to moderate sciatic nerve compression and irritation. Anti-inflammatory medications can also be helpful.

Surgical removal of structures that affect the sciatic nerve is possible, but many people experience recurring symptoms after surgery for a herniated disc or narrowing of the opening.

In some cases, surgical repair of the sciatic nerve is possible, especially if the injury is recent. New methods, including tissue grafts and stem cells, are currently being investigated as possible methods to regenerate injured sciatic nerves .

Deciding how to treat sciatic nerve disease requires a careful medical examination and is based on your situation.

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