The sciatic nerve is the largest and longest nerve in the body, originating from the lumbar and sacral nerve roots in the lower spine and traveling through the buttock and down the back of each leg to the foot.
Where the sciatic nerve runs and what causes it to become irritated
Your sciatic nerve forms from several nerve roots that exit the lower lumbar spine and sacrum, then merge into a single large nerve that passes through the buttock — typically beneath the piriformis muscle — and continues down the back of the thigh, branching into smaller nerves that supply the lower leg and foot. Because of its length, sciatic nerve irritation can produce symptoms at any point along its path: pain in the buttock, aching through the thigh, burning or tingling in the calf, numbness in the foot, or weakness in muscles the nerve supplies. The most common cause of sciatic nerve irritation is compression at the nerve root level — typically from a herniated disc or bony narrowing in the lower lumbar spine. Less commonly, the nerve is compressed further down its path, such as at the piriformis muscle, which can produce a nearly identical symptom pattern.
Why sciatica symptoms can be misleading about the source
Pain, tingling, or numbness that runs down the leg — commonly called sciatica — is a symptom, not a diagnosis. The cause can be lumbar disc herniation, spinal stenosis, sacroiliac joint referral, piriformis syndrome, or several other conditions. Effective treatment depends entirely on identifying which structure is irritating the sciatic nerve and why.
Why imaging doesn't always explain sciatic nerve pain
MRI findings of disc bulges and nerve root compression are common in people with no leg symptoms at all, which means the scan doesn't always correspond to what's generating the pain. Clinical assessment — evaluating the pattern of symptoms, which movements provoke them, and what examination findings are present — is what points to the right source and the right treatment approach.
How Sword Health can help
A physical therapist can assess your sciatic nerve symptoms, identify the likely source of irritation, and guide you through a targeted plan to reduce nerve compression and restore function. Sword connects you with that expertise from home, with clinical oversight throughout your recovery.
About the author
Carolina Moreira
Medical Director of Clinical Development at Sword Health
