The sciatic nerve is the longest and thickest nerve in your body, running from your lower back down through each leg. It originates from nerve roots in the lower spine (specifically the L4 through S3 vertebrae), where multiple nerve fibers converge into a single large nerve that controls movement and sensation in most of your lower body. When this nerve is compressed or irritated, the resulting pain, known as sciatica, affects roughly 5 to 10% of people who experience low back pain.
Where the Nerve Runs
The sciatic nerve forms deep in the pelvis, where nerve fibers from five spinal levels merge together. From there, it exits through an opening in the pelvis called the greater sciatic foramen, passes beneath the gluteal muscles, and travels down the back of each thigh. Around the level of the knee, it splits into two major branches: one that serves the front of the lower leg and top of the foot, and another that serves the calf and sole of the foot.
This path explains why problems at the spine can produce symptoms all the way down to your toes. A pinched nerve root near your lower vertebrae can send pain, tingling, or numbness along the entire length of the nerve’s route. The nerve carries both motor signals (telling muscles to move) and sensory signals (relaying touch, temperature, and pain back to the brain), so compression can affect both movement and sensation.
What the Sciatic Nerve Does
On the motor side, the sciatic nerve powers the muscles in the back of your thigh (hamstrings) and, through its branches below the knee, nearly every muscle in your lower leg and foot. This is why severe sciatic nerve damage can make it difficult to bend your knee, lift your foot, or push off while walking. A condition called “foot drop,” where you can’t lift the front of your foot, is one recognizable sign of significant sciatic nerve impairment.
On the sensory side, the nerve and its branches provide feeling to most of your leg below the knee, including the shin, calf, top and bottom of the foot, and toes. The specific pattern of numbness or tingling you experience can help pinpoint which nerve root is involved, since each root corresponds to a slightly different strip of skin.
Common Causes of Sciatic Nerve Pain
Herniated discs in the lumbar spine are the leading cause of sciatica. Spinal discs sit between your vertebrae and act as cushions. Over time, they lose fluid and elasticity, becoming brittle and prone to cracking. When part of a disc bulges out and presses against a nearby nerve root, it triggers the characteristic shooting pain down the leg. Traumatic injuries can also herniate a disc, though this is far less common than gradual wear and tear.
Other causes include spinal stenosis (narrowing of the spinal canal), bone spurs from arthritis, and muscle-related compression. One well-known example is piriformis syndrome, where the piriformis muscle deep in the buttock tightens or spasms and presses against the sciatic nerve. This produces similar symptoms to a disc problem but originates in the hip rather than the spine. Piriformis syndrome is largely a diagnosis of exclusion, meaning doctors arrive at it after ruling out spinal causes, since there’s no single reliable test for it. Characteristic signs include buttock pain that worsens while sitting and pain during specific hip rotation movements.
The annual incidence of a sciatica episode in the general population is 1 to 5%, with disc-related sciatica specifically estimated at about 2.2% per year. It most commonly affects people between ages 30 and 50, and risk factors include prolonged sitting, obesity, diabetes, and physically demanding occupations.
What Sciatica Feels Like
Sciatica typically produces a sharp, burning, or electric-shock-like pain that radiates from the lower back or buttock down the back of one leg. It rarely affects both sides simultaneously. Many people also experience numbness, tingling, or muscle weakness in the affected leg or foot. The pain often worsens with sitting, coughing, or sneezing, since these actions increase pressure on the spinal discs.
Symptoms can range from a mild, intermittent ache to severe pain that makes standing or walking difficult. Most episodes resolve within 4 to 6 weeks with conservative care, though some people develop chronic or recurring symptoms. The location of your symptoms provides a clue about the source: pain mostly in the buttock and upper thigh may point to a higher nerve root or piriformis involvement, while pain extending to the foot and toes usually suggests a lower lumbar disc issue.
How Sciatic Nerve Problems Are Diagnosed
Diagnosis typically starts with a physical exam. One of the most commonly used bedside tests is the straight leg raise, where you lie on your back and the examiner lifts your straightened leg. If this reproduces your radiating leg pain, it suggests nerve root irritation. This test is quite sensitive, catching 72 to 97% of disc herniations, but it’s not very specific (only 11 to 66%), meaning other conditions can also produce a positive result. A variation called the crossed straight leg raise, where lifting the unaffected leg triggers pain in the symptomatic leg, is less sensitive (23 to 42%) but much more specific (85 to 100%), making it a stronger confirmation when positive.
Imaging is not always necessary for a first episode of sciatica, since most cases improve on their own. MRI becomes important when symptoms are severe, persist beyond several weeks, or include red flags suggesting a more serious problem. For suspected piriformis syndrome, doctors may use ultrasound or EMG testing to evaluate the muscle and nerve directly.
Serious Warning Signs
In rare cases, a large disc herniation can compress the bundle of nerves at the base of the spinal cord, a condition called cauda equina syndrome. This is a surgical emergency. The key warning signs are sudden loss of bladder or bowel control, rapidly worsening weakness in one or both legs, and numbness in the groin or inner thigh area (sometimes called “saddle anesthesia” because it affects the area that would contact a saddle).
Early recognition matters enormously here. Research has found that many published guidelines for cauda equina syndrome emphasize symptoms of late, often irreversible damage rather than the earlier signs that would allow timely intervention. True red flags, the kind that warn of avoidable damage, include bilateral leg symptoms (pain or weakness in both legs), difficulty initiating urination, and reduced sensation in the perineal area. If you develop any of these alongside sciatica, seek emergency care immediately rather than waiting for your next appointment.
Treatment and Recovery
Most sciatica improves with time and self-care. In the first few days, gentle movement is generally more helpful than strict bed rest, which can actually slow recovery. Over-the-counter pain relievers and anti-inflammatory medications help manage symptoms while the underlying irritation settles. Applying ice in the first 48 to 72 hours, followed by heat, can also provide relief.
Physical therapy is one of the most effective treatments for persistent symptoms. A therapist can guide you through stretches and strengthening exercises targeting the core and lower back muscles that support your spine. Specific stretches for the piriformis muscle are useful when that muscle is contributing to the compression. Many people notice significant improvement within 4 to 6 weeks of consistent exercise.
For pain that doesn’t respond to conservative measures, epidural steroid injections can reduce inflammation around the irritated nerve root and provide temporary relief lasting weeks to months. Surgery, typically a procedure to remove the portion of disc pressing on the nerve, is reserved for cases with severe or progressive weakness, cauda equina syndrome, or pain that persists despite months of non-surgical treatment. Most people who do need surgery experience significant improvement, with the majority returning to normal activities within a few weeks to months.