The sciatic nerve is the largest nerve in the body: it runs from the lumbosacral region to the foot. When irritation or compression occurs along this path, a person feels pain radiating from the lower back into the buttock and leg. Below is information on the mechanism, symptoms, and causes of sciatica.
What sciatic nerve inflammation is
The nerve fibers carry sensation from the back of the thigh, part of the lower leg, and the sole, and motor commands to the muscles of the back of the knee and lower leg. A disc herniation or narrowing of the canal creates an obstacle along this route, impulses travel with distortion, and the brain receives an altered picture. In everyday speech this condition is called sciatic nerve inflammation, although it is more accurate to speak of irritation or compression.
The word "ischias" comes from ancient Greek, where ισχιας meant "hip." Sciatica is a symptom of a problem with the sciatic nerve, not a separate disease.
Main symptoms of sciatica
The picture is usually one-sided: the buttock and the back of one leg, often involving the foot and toes. Pain may appear suddenly, but it often builds gradually and intensifies with movement, coughing, and sneezing. The back can hurt too, but the leg pain is usually stronger.
- sharp, burning pain along the back of the leg;
- tingling, a "pins and needles" sensation;
- numbness;
- weakness in the leg.
Causes of sciatic nerve inflammation
The most common culprit is an intervertebral disc herniation: the soft layer between the vertebrae bulges and presses on the nerve, and this happens more often with age. Less common are narrowing of the spinal canal (stenosis), displacement of a vertebra (spondylolisthesis), and trauma such as a pelvic fracture.
In some cases the cause cannot be found. Sciatica is also associated with lumbar radiculitis, osteochondrosis, and piriformis syndrome. Smoking increases the likelihood of encountering this condition.
How sciatica differs from other pain in the lower back and leg
The main guide is the area: the pain travels along the nerve downward toward the foot and involves the back of the thigh. If only the back hurts, the likelihood of sciatica is low: isolated lower back pain rarely turns out to be its manifestation. Sciatica is usually one-sided and tends to return if it has occurred before.
How the diagnosis is made
Diagnosis uses, in particular, MRI and CT of the spine; they show the condition of the discs, spinal canal, and vertebrae.
When leg pain requires urgent medical attention
A routine visit is needed if after home measures there has been no improvement within a few weeks, the pain is worsening, or it interferes with everyday activities. Most often sciatica resolves within a few weeks or months, sometimes it lasts longer and can return.
Sciatica by itself is not a reason to call an ambulance. Call 103 or 112 if the pain has appeared on both sides; if weakness or numbness of both legs is pronounced or increasing; if the genital area or the skin around the anus is numb; if it is difficult to start urinating, urine does not pass, or there is incontinence; if the urge to defecate is lost or there is fecal incontinence.
This reference material explains how the phenomenon works but does not replace a consultation with a doctor who sees you, your history, and your scans.
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This content is for reference and does not replace a doctor's consultation. Medical disclaimer