When the spasm comes from a narrowed canal
Legs that ache or go heavy when you stand and walk, and ease the moment you sit or lean forward.
Spinal stenosis means the space around the spinal cord or the nerve roots has narrowed. Usually it's gradual: thickened ligament, arthritic change at the facet joints, disc height loss, sometimes a vertebra that has slipped slightly forward. The space available to the nerves shrinks.
Crucially, that space changes with posture. Extending the spine — standing tall, walking, arching back — narrows it further. Flexing forward opens it up. That's why the pattern is so distinctive.
Why it produces spasm
Nerves that are crowded tolerate less. When you stand and walk, the canal closes down, the nerves become irritated, and the surrounding muscles receive the same instruction they always do: stabilise, restrict, protect. The low back tightens, the legs get heavy, and the whole thing eases within a minute or two of sitting down.
Over time the muscles are doing this so often that they never fully switch off, and a full spasm can be triggered by very little.
What it usually feels like
- Legs that ache, burn, or feel heavy and unreliable after a few minutes of standing or walking
- Rapid relief on sitting, squatting, or leaning on a shopping trolley
- Walking uphill or pushing a cart is easier than walking downhill or standing still
- Often both legs, though rarely symmetrical
- More common after 50, and it tends to arrive gradually rather than in one dramatic moment
The "shopping trolley sign" is the classic one. If you can walk the length of a supermarket leaning on a cart but not the length of your own street upright, that's the pattern.
During the acute phase
The immediate steps hold: stop, position, heat, breathe. Stenosis adds one useful adjustment.
Flexed positions usually win. Lying on your back with knees drawn up, or on your side curled, tends to be far more comfortable than lying flat or face down. A recliner is often better than a bed. This is close to the opposite of what suits an irritated disc, which is one reason knowing your pattern matters.
Short and often beats long and rare. Once you're moving again, several short walks with sitting breaks work better than one long one that ends in a flare.
What tends to make it worse
- Standing still, queueing, standing at a counter
- Extension work — back arches, prone press-ups, overhead reaching
- Long downhill walks
- Sleeping flat on the stomach
Get assessed if
Urgently, for any loss of bladder or bowel control, saddle numbness, or weakness that is getting worse.
Otherwise: if your walking distance is shrinking month by month, if you're having falls or a foot is catching, or if the leg symptoms are becoming constant rather than positional. Stenosis is one of the conditions where imaging and a proper conversation about options — conservative management, injection, decompression — is worth having rather than putting off.
Get the emergency protocol before the next one
The full 21-page guide: what to do in the first 48 hours, the day-by-day recovery, and how to come back without re-triggering it. Free.
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Other patterns
- Sciatica and nerve irritation Pain that travels into the buttock or down the leg, with the low back locking to protect the nerve root.
- Disc bulge or herniation Pain that spikes with bending, sitting and coughing, and a back that locks the moment you move the wrong way.
- Facet joint irritation A sharp local catch on arching, twisting or standing up, with pain that stays close to the spine.
- SI joint irritation Pain in one dimple of the low back or deep in the buttock, worse on stairs, standing on one leg, and rolling over in bed.
- Overload, fatigue and stress The episode with no dramatic cause — a sneeze, a sock, the third bad night of sleep in a stressful month.