What causes sciatica?

True sciatica is a nerve root problem, not a muscle problem. The two feel different once you know what to check. Nerve pain travels in a line. It runs down the back or side of the leg, sometimes past the knee, sometimes into the foot. Often numbness or burning sits on top of the ache. It comes from pressure and chemical irritation at a specific root, most often L4, L5 or S1. That is where a disc fragment or narrowed foramen touches the nerve as it exits the spine.

Two biological drivers are doing the work. The first is mechanical: a herniated disc or narrowed foramen is physically deforming the root. The second is chemical. The leaked disc material is inflammatory in its own right. It sensitizes the nerve no matter how hard it is being pressed. That is why pain can be severe even when compression looks modest on a scan. A third driver is usually the job. Long stretches of sitting, or repeated lifting and twisting, load the same discs daily. Warehouse, logistics and airport-ground workers along the Woodson corridor carry more of this than a desk-only population. The disc is where it hurts. The forklift and the pallet are often why it keeps happening.

What is mistaken for sciatica?

Several structures can send pain down a leg without any nerve root involved. Mistaking one for another is the most common reason a plan fails.

Foraminal stenosis is narrowing of the tunnel the nerve exits through, from bone spurs or a bulging disc. It produces true radicular pain (pain along the nerve) by the same mechanism as a herniation. But it does not resorb (shrink back) the way a fragment of disc material can. It tends to worsen slowly rather than ease on its own. That difference changes how patient the plan can afford to be.

How is sciatica diagnosed?

The exam comes first: reflexes, strength testing at the ankle and big toe, straight-leg raise, and pressing on the hip rotators and the sacroiliac joint. An MRI, when warranted, is read against that exam, not on its own. Disc bulges show up on the scans of many pain-free adults your age. So the job is confirming that the level the scan flags is the level your body is complaining about. When more than one structure is plausible, a diagnostic injection becomes the tiebreaker. An epidural steroid injection targeted at a single level tells us something a scan cannot, because relief there, even briefly, implicates it.

Does an epidural steroid injection help sciatica?

An epidural does not shrink a disc fragment or widen a foramen. It quiets the chemical inflammation around the root long enough for you to sleep, move and let the underlying problem run its course. For a true herniation, that course often leads toward resorption. Pooled cohort data published in 2024 in Clinical Spine Surgery tracked patients across dozens of studies. It found that about two-thirds of herniated fragments get visibly smaller within months, even without an operation. The biggest and angriest-looking extrusions tended to shrink the fastest. That is the case for treating the interval, not the anatomy.

Two-thirds is the working number: most lumbar disc herniations get smaller on their own within months — a population pattern, not a guarantee for any single disc.

The terrain underneath the disc

Two people can carry the same MRI and heal at very different rates. The difference is often metabolic before it is mechanical. Insulin resistance and systemic inflammation raise the baseline that the disc’s own inflammatory response builds on. They also impair the small-vessel circulation the nerve root and the healing disc both depend on. That is why bloodwork is part of a first consultation. It is also why Acceptance and Commitment Therapy carries equal weight in the plan alongside the injection. It is delivered by this practice’s own behavioral clinician, never handed off to an outside referral. Metabolic health and pain and sleep, movement and behavior cover the mechanism in full.

When does sciatica need surgery?

For most sciatica, surgery is not part of the plan. Conservative care and interventional treatment resolve most cases. A fragment given time to resorb often makes the operation unneeded in hindsight. What changes the math is weakness that is new or getting worse, not pain severity alone. Pain, however intense, is not by itself a reason to operate. A foot drop or a deficit progressing over days is different, because a nerve that has been squeezed for too long does not reliably bounce back once it is finally freed. When conservative and interventional options are exhausted, this practice performs microdiscectomy. The full decision is covered on herniated disc.

Red flags, in plain terms

Frequently asked questions

How do I know if it is my disc or my piriformis?

A true nerve root pattern shows a matching reflex, strength or sensation change. It gets worse with sitting and a straight-leg raise. Piriformis pain sits more in the buttock, gets worse with hip rotation, and leaves the spine exam clean. A similar spine-versus-muscle split is covered on facet joint pain.

Will an MRI tell me what is wrong?

Only when read against your exam. Disc bulges appear on the scans of many pain-free people. So the MRI confirms or rules out a level your exam has already pointed to. What to expect covers how the first visit works.

How long before it gets better on its own?

It varies, but a meaningful share of herniations shrink over weeks to months. An epidural aims to make that interval bearable rather than shorten it. Epidural steroid injection explains the mechanism.

Do I need surgery?

Most people do not. Surgery enters the conversation when weakness is new or progressive, not because pain is severe. The scoped decision for a herniated disc is covered on herniated disc.

Why did my back injection not help my leg pain?

Often because the source was never a nerve root. The sacroiliac joint and piriformis both produce leg pain an epidural was never aimed at. That is why re-examination matters more than repeating the injection. See when injections stop working.

What triggers sciatica pain?

Pressure and chemical irritation at a nerve root, most often L4, L5 or S1. A herniated disc or a narrowed foramen deforms the root. Leaked disc material inflames it, even when compression looks modest on a scan. Long stretches of sitting and repeated lifting and twisting load the same discs every day, which is why the pain keeps returning in physical jobs.

How do you fix sciatic nerve pain?

Find the source first, because a disc, a narrowed foramen, the piriformis muscle and the sacroiliac joint can all send pain down the leg. The exam, and when needed one targeted injection, sorts that out. For a herniated disc, an epidural quiets the inflammation while the fragment often shrinks on its own. Surgery enters the conversation when weakness is new or getting worse.

What is the worst thing you can do for sciatica?

Treat the wrong structure. Mistaking one source for another is the most common reason a sciatica plan fails, and repeating an epidural that never reached the problem only delays the answer. Ignoring new weakness is the other mistake: a foot drop or a deficit that progresses over days needs prompt care, because a nerve squeezed too long does not reliably bounce back.

Related reading

• Herniated disc
• Spinal stenosis
• Sacroiliac joint pain
• Epidural steroid injection
• After a car accident
• Hip arthritis