Location of the sciatic nerve in relation to sciatica
Where is the sciatic nerve?
The sciatic nerve is largest, longest in widest nerve in humans and other animals that starts in the lower back, runs through the buttocks and down the leg into the foot, ending at the great toe. At its widest part, it is a big around as the thumb of that individual.
It is one nerve that starts from five different levels of the spine. The sciatic nerve is formed on the right and left sides of the lower back just a little above and a little below the beltline, by the roots of the 4th, and 5th lumbar nerve root and the 1st, 2nd and 3rd sacral nerve roots. It travels down the back of each buttock and leg, and as it does it gives off nerve branches that supplies nearly almost the skin of the entire leg with sensory awareness, and all the muscles of the back of the thigh, and those of the leg and foot with motor control.
In addition to the sciatic nerve providing motor power and sensory feelings along the entire leg, it also provides all the reflexes to the legs. This arrangement provides motor control to the hamstring muscles at the back of the thigh, as well as all muscles in the lower leg and feet. Because of this widespread distribution, when the sciatic nerve is impaired it can lead to widespread and intense pain, muscle weakness, numbness and tingling in the leg, ankle, foot, all the way down to the great toe.
Sciatica is the most common way for pain to be caused by compression of the spinal nerves. When sciatica and low back pain occur together because of nerve root irritation the sciatic leg pain is usually much worse than the back pain.
When any of these five starting points becomes irritated or compressed considerable sciatic nerve pain can be felt at any point all along the length of the nerve. This painful condition is known as sciatica. Common causes of sciatica include lumbar disc herniation or bulging, spondylosis (degenerative disc disease), lumbar spinal stenosis, spondylolisthesis, and piriformis syndrome. Common ways for sciatica to start suddenly include coughing, sneezing, straining at stool, and during heavy lifting in which twisting is involved, causing disruption of the spinal alignment and soft tissue elements near the sciatic nerve roots.
Sciatica pain based on anatomy
Sciatic nerve irritation can start easily because of two anatomical relationships that are unique in the body.
Sciatica has a special relationship to the piriformis muscle, hence the piriformis syndrome. The five nerve roots that make up the sciatic nerve (4th and 5th lumbar, and 1st, 2nd and 3rd sacral) are separated at first but come together or unite into the sciatic nerve on the surface of the piriformis muscle. If the piriformis muscle goes into spasm or otherwise creates a state of irritation to the various nerve roots that lay over it, it can in turn excite the sciatic nerve and cause sciatic neuritis pain (sciatica) to start in the leg.
Also, sciatica has a special relationship to the discs of the lower lumbar spine. As the nerves that make up the sciatic nerve exit the spine, they are in very close relationship to the inner portion of the lower lumbar discs. If these discs bulge, herniate, or extrude their jelly-like protein contents, this physical contact can create chemical irritation that will cause inflammation of the nerve, resulting in pain and/or numbness anywhere in the buttock or leg.
Sciatica symptoms based on location of nerve roots
The exact location and type of sciatica symptoms that are felt (nerve pain, numbness, tingling, or weakness) will be different depending where the sciatic nerve irritation or pressure occurs. The specific sciatica symptoms are dependent on the five different points of origin in the lower back:
- Sciatica from L4 nerve root
Symptoms of sciatica originating from the L4 nerve root: pain and/or numbness in the medial or inner lower leg and foot; motor weakness reduces ability to bring the foot upwards (raise toes and walk on heel).
- Sciatica from L5 nerve root
Symptoms of sciatica originating from L5 nerve root: pain and/or numbness at the top of the foot, particularly in the area between the great toe (big toe) and the second toe; motor weakness reduces ability to extend the big toe and ankle (known as foot drop).
- Sciatica from S1 nerve root
Symptoms of sciatica originating from S1 nerve root: pain and/or numbness to the lateral or outer foot; motor weakness reduces ability to raise the heel off the floor or walk on the tiptoes. .
- Sciatica from sacral nerve root irritation due to sacroiliac joint dysfunction
Symptoms of sciatica originating from sacroiliac joint dysfunction: sciatica-like pain or numbness often described as a deep dull ache within the entire leg rather than a well-defined area of the leg as occurs with true nerve root sciatic nerve pain. .
- Sciatica from pressure or irritation related to the piriformis muscle
Symptoms of sciatica from a piriformis syndrome: sciatica-like pain and/or numbness in the leg that usually starts in the buttock , not the low back, and is usually mild below the knee and intense above the knee; noted for an absence of lower back pain.
Classic sciatica nerve pain
Sciatic neuritis is characterized by one or more of the following:
- Pain worse when sitting
- Constant pain on only one side of the buttock or leg, rarely bilateral
- Intensely burning pain or tingling sensation in the leg, never a dull ache
- Sharp burning pain making it difficult get out of chair or stand still
- Pain improves when lying down or slowly walking
- Weakness of the leg making it difficult to move the leg or foot, not pain limiting movement
- Inability to bear weight on the side of sciatic involvement due to increase of pain
Once the location of the sciatic nerve is understood it is much easier to anticipate many of the symptoms of sciatica and to know how to treat the problem correctly.