When the spasm is protecting a disc

Between each pair of vertebrae sits a disc: a tough fibrous ring with a gel-like centre. When that ring weakens, the centre can push outward (a bulge) or push through (a herniation). If the displaced material contacts or chemically irritates a nerve root, you get pain — and your spinal cord gets a very clear reason to shut the segment down.

Why a disc problem produces such a hard spasm

Two things are happening at once.

There's mechanical pressure — physical contact between disc material and a nerve root or the surrounding structures. And there's chemical irritation: the nucleus of a disc contains inflammatory proteins that the body has never been exposed to, because the disc has no blood supply of its own. When they leak out, the local tissue responds as though to a foreign substance.

The nervous system's answer is to lock the whole segment so that movement can't make the displacement worse. The multifidus and erector spinae go into continuous emergency contraction. That protection is often more disabling in the first week than the disc problem itself.

What it usually feels like

• Sudden onset, often during a bend-and-twist, a lift, or sometimes something trivial the day after a heavy day
• Sharp catching pain with specific movements rather than constant ache
• Worse sitting and worse bending forward, better standing or walking for many people
• Coughing, sneezing or straining sends a spike through the back or down the leg
• May or may not include leg symptoms, depending on whether a nerve root is involved

Not every disc bulge hurts. Plenty of people have them on imaging with no symptoms at all. The bulge matters when it's irritating something.

During the acute phase

Rest in the position that reduces the pain, apply heat, keep the breathing slow — the standard protocol. Beyond that:

Most people with an irritated disc are more comfortable extended than flexed. Lying on your back with knees bent, or lying face down propped on forearms if that's tolerable, often eases things. Sitting slumped is usually the worst position available.

Log-roll to get in and out of bed. Shoulders, ribs and pelvis turning as one unit, then push up with the arms while the legs swing down. Sitting straight up out of bed loads the disc at exactly the wrong angle.

Don't test it. The urge to bend forward every few hours to check whether it's improving is understandable and it prolongs the whole thing.

What tends to make it worse

• Sitting for long stretches, particularly in a car
• Forward bends and toe-touch stretches
• Lifting anything in the first week, however light, at a distance from your body
• Spinal manipulation during an acutely irritated phase, unless a clinician who has examined you says otherwise

Get assessed if

Immediately, for loss of bladder or bowel control, saddle numbness or progressive weakness in both legs — a large central herniation is rare but it is a surgical emergency.

Otherwise: if pain travels below the knee, if you have numbness or weakness that is not improving over a couple of weeks, or if this is a repeat episode. Most disc-related pain improves without surgery, but the ones that don't need to be identified early rather than late.

If you're in an acute spasm as you read this, start with the three immediate steps. This page is for working out what set it off.