What is Sciatica
The sciatic nerve is not only the largest but also the strongest nerve in the human body. The nerve starts from five nerve roots, two that exit from the low back and three that exit from the sacrum.
The sciatic nerve travels from the low back, through the buttock, and down the leg. It then goes past the hip, knee, calf, ankle, foot, and all the way to your toes.
The brain connects to the lower leg and foot through this nerve. It sends directions to the muscles of the leg and receives sensation back. The sciatic nerve is crucial for the control of movement, balance, and feeling in the leg.
The sciatic nerve can become irritated
When it does it can cause pain in the form of a burn, ache, sharp, shooting, or dull pain. It also can cause numbness, tingling, and loss of strength in the leg or foot. Sciatica may occur suddenly or gradually over time creeping down the leg.
Most common symptoms of sciatica
- Sharp or shooting pain in the leg or side of the foot
- Numbness, pins, and needles in leg or side of the foot
- Pain or numbness top of the foot, usually between the big toe and second toe
- Electric shock burning or prickling sensations in the leg or foot
- Weakness in the leg or foot
- Weakness in lifting the big toe or the ankle up
- Difficulty walking on the heels or standing on the toes
There are two types of sciatica
1. Neurogenic sciatica
This type of sciatica is due to compression of the sciatic nerve or the smaller nerve roots where it starts. What type of symptoms this sciatica displays depends on the amount of pressure on the nerve.
With neurogenic sciatica, the back pain is not as severe as the leg pain.
An at this point examination may show abnormal neurological findings. Things like a loss of reflex, muscle weakness, and sensory changes such as numbness.
What causes neurogenic sciatica
Disc problems
The discs between the vertebra can bulge, herniate, protrude, or extrude. When any of these occur there can be direct pressure spinal nerve roots that make up the sciatic nerve. They can also press on the spinal cord itself within the spine, causing sciatica.
Tight muscles
The muscles of the buttocks and top of the legs can get involved. They put pressure on the sciatic nerve irritating it and causing symptoms.
2. Referred Sciatica
This type of sciatica is usually due to a joint problem in the low back or a muscle problem in the low back or pelvis.
This type of sciatica does not have the sensation of numbness or tingling or muscle weakness. The pain is more often felt in the back and less in the leg and neurological findings on an exam can be absent.
Contributing factors for sciatica
1. Abnormal movement of the spine
This is when the low back has restricted movement and cannot reach its full range of motion. When this occurs the joints can become inflamed. The muscles around the joints can tighten even more and in some cases spasm. When this occurs the nerve roots making up the sciatic nerve can become irritated.
Poor movement and restricted of the low back can come from:
- previous trauma
- poor posture
- home and work environments that place stress on the spine.
2. Sacroiliac joint dysfunction
This joint is between the large bone at the end of the spine called the sacrum and the pelvis. It is important because it helps transfer weight and forces between the upper body and legs.
The sciatic nerve runs close to this joint. If the SI joint becomes damaged and inflamed it can cause irritation to the sciatic nerve.
Degenerative joint disease or osteoarthritis
The disc spaces between the vertebra can become narrowed. This decreases the size of the hole where the nerve root exits the spine. This hole is called the vertebral foramina. When narrowed it can result in nerve root irritation and sciatica.
When the disc space narrows the actual disc is thinning. The thinning disc releases inflammatory proteins. This also can irritate the nerve root.
3. Spinal stenosis
This condition can involve several factors, but degeneration is one of them. With stenosis, the spinal canal, which the spinal cord passes through, becomes narrowed. This restriction of space can put pressure on the spinal cord causing sciatica.
4. Spondylolisthesis
This is the name given when one vertebra slips forward over the vertebra below it. There can be a loss of disc height between the vertebrae when this occurs. This again narrows the space where the nerves exit the spine. A common location for this problem is at the base of the spine. This is where the nerve roots for the sciatic nerve exit and why this condition can cause sciatica.
5. Pregnancy
As the fetus grows it develops in size and weight. The result is the curve in the low back can increase due to the mother’s center of gravity shifting forward. This can cause irritation to the low back nerve roots and cause sciatica in the legs. The baby’s position also might irritate the nerve roots involved in sciatica. Sometimes pre-existing back issues flare up during this time.
6. Piriformis Syndrome
The sciatic nerve usually runs below the piriformis muscle as it leaves the spine. Sometimes it runs through the piriformis muscle. If this muscle tightens or goes into spasm it can irritate that area of the sciatic nerve. The piriformis muscle plays a role in stabilizing the low back. Because of this, it will tighten as a protective mechanism if the back is at risk or not working well. For this reason, the piriformis itself is rarely the sole cause of sciatica.
Chiropractic often helps sciatica. It does this by relieving the strain on the nerve caused by many of the conditions above.