"I've got sciatica," people say, pointing vaguely at one buttock. Sometimes they're right. Often they're describing something else entirely — a grumbling facet joint, a strained glute, a nerve pinched somewhere far from the spine. And just as often, someone who waves it away as "only a trapped nerve" has a textbook case of the real thing. The words get swapped so freely that the diagnosis loses its meaning, and with it, the guidance that actually helps.

Sorting out which one you have matters. It changes what you should do on a bad day, what to avoid, and how quickly you need to be seen by someone qualified.

Sciatica is a description, not a diagnosis

The sciatic nerve is the thickest nerve in the body. It forms from nerve roots in the lower back, passes through the buttock, and runs down the back of the leg, branching as it goes. Sciatica simply means pain travelling along that route. It tells you where the trouble is showing up, not what is causing it.

That's why two people with identical sciatica symptoms can have completely different problems underneath. One might have a disc pressing on a nerve root. Another might have narrowing of the spinal canal. A third might have irritation where the nerve exits the spine. Same word, different mechanics, different recovery times.

What people usually mean by "a trapped nerve"

"Trapped nerve" is everyday language rather than a clinical term. It can mean almost any nerve being squeezed or irritated anywhere in the body — the median nerve at the wrist in carpal tunnel syndrome, the ulnar nerve at the elbow, the peroneal nerve at the side of the knee, or a nerve in the lower back.

In the context of back pain, it usually means one of two things. Either a nerve root is being compressed where it leaves the spine — which is, in effect, sciatica — or something nearby is producing a sharp, catching sensation that feels nerve-like but isn't. A locked facet joint or a deep muscle spasm can both do a convincing impression.

How the symptoms actually differ

The single most useful question is not "how much does it hurt?" but "where does it go, and what else comes with it?"

Where the pain travels

True sciatica follows a line. It typically starts in the lower back or buttock and runs down the leg, often past the knee, into the calf, ankle or foot. It may follow a narrow band rather than the whole leg. Pain from back joints or the sacroiliac joint tends to be a duller ache, usually in the buttock or back of the thigh, and it rarely travels far below the knee.

What it feels like

Nerve pain has a distinctive quality: electric, shooting, burning, sometimes like a hot wire. It often changes with a cough, sneeze or strain, because that briefly raises pressure around the nerve roots. Ordinary referred pain from a joint or muscle doesn't usually behave that way.

What comes with it

This is where nerves give themselves away. Along with the pain you may notice pins and needles, numbness in a specific patch, or weakness — a foot that slaps down, a leg that gives way on stairs. Those are neurological signs, and they point towards a nerve being genuinely affected rather than irritated.

What makes it better or worse

Disc-related sciatica is often worse sitting, bending forward or lifting, and easier standing or walking. Pain from spinal narrowing tends to do the opposite: it eases when you lean forward or sit, and worsens when you stand and walk any distance. Neither pattern is a perfect test, but the direction of travel is informative.

A quick checklist to hold in mind:

  • Shooting pain below the knee, in a band — strongly suggests a nerve root is involved.
  • Pins and needles or numbness in a defined area — a nerve signature.
  • Weakness, or a heavy, unreliable leg — needs assessing promptly.
  • Pain that changes with a cough or sneeze — more likely nerve-related.
  • A dull ache in the buttock only, no leg symptoms — often joint, muscle or referred pain.
  • Pain that jumps around or moves from day to day — less likely to be a single compressed nerve.

What tends to cause each pattern

When sciatica is genuine, the usual culprits are a bulging or herniated disc pressing on a nerve root, narrowing of the spinal canal, or a vertebra that has slipped slightly forward. Less commonly, the nerve is irritated where it passes through the buttock — sometimes called piriformis syndrome, though this diagnosis is debated and often over-applied.

Problems labelled loosely as trapped nerves elsewhere have their own causes: sustained pressure, repetitive posture, swelling, or an awkward stretch. In the back, that might be a joint that has become stiff and inflamed, or a muscle in spasm guarding an area after a strain.

Red flags that override everything else

Some symptoms don't belong in a comparison article — they need urgent attention. If any of the following appear, contact emergency services or go to A&E rather than booking a routine appointment:

  • Numbness around the saddle area, genitals or inner thighs
  • New difficulty passing urine, or loss of bladder or bowel control
  • Rapidly worsening weakness in one or both legs
  • Foot drop — the foot drags and you can't lift it properly
  • Back pain with fever, unexplained weight loss, or a history of cancer
  • Severe pain following a fall or significant injury

These are uncommon, but they are the reason a proper assessment is worth having rather than self-diagnosing from a symptom list.

What an assessment looks for

A physiotherapist or GP will ask about the pattern of your pain, then run through simple tests: raising your straight leg to see where symptoms start, checking reflexes, testing sensation in different patches of skin, and comparing strength between legs. None of these are glamorous. Together, they separate nerve compression from joint and muscle pain surprisingly well.

Scans are useful in the right circumstances but not as a first step. Disc bulges and age-related changes show up on scans of people with no pain at all, so a picture alone rarely explains your symptoms. The history and examination matter more.

What to do next

Keep moving. Resting flat for days tends to make back and nerve pain worse, not better. Short, gentle walks, changing position regularly, and avoiding the specific movements that send pain shooting down your leg are sensible first steps.

Write down what you notice over the next week: where the pain starts and finishes, whether it crosses the knee, what triggers it, and whether numbness or weakness is part of the picture. That record is genuinely useful at an appointment and will get you a clearer answer faster.

If symptoms are mild and improving, give it a couple of weeks. If they're severe, getting worse, or you're noticing weakness or numbness, book an assessment — and use the red flags above as your line for seeking urgent care. This is general information, not a diagnosis, so for anything that worries you, speak to a GP, a physiotherapist or NHS 111.

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