What a radiculopathy is

A nerve root leaves the spinal canal through a foramen at each level. Anything that narrows that space or inflames its contents — a disc protrusion, a hypertrophied facet, a thickened ligament, a spondylolisthesis — can make the root symptomatic. The result is radicular pain, which is qualitatively different from the aching of a joint: sharper, electric, following a path, and often accompanied by a genuine neurological finding.

It is worth being precise about a distinction that gets blurred. Radicular pain is pain generated by an irritated root. Radiculopathy means the root is not conducting properly — numbness in a dermatome, weakness in a myotome, a diminished reflex. You can have the first without the second. Having the second changes the urgency and sometimes the treatment.

Which level, from the pattern

• L4 — pain across the front of the thigh into the inner shin, weak knee extension, reduced knee reflex.
• L5 — down the outer thigh and shin into the top of the foot and the great toe, weak toe and ankle dorsiflexion. This is the root behind a foot that slaps or catches.
• S1 — down the back of the thigh and calf into the outer foot and little toe, weak plantar flexion, reduced ankle reflex. Trouble rising onto the toes on one side.

Those maps overlap between people and no textbook diagram is exact in any individual. They are strong enough, though, that a careful examination usually predicts the level the imaging will confirm — and, more usefully, catches the cases where the imaging finding and the symptoms do not match.

What the natural history actually is

Most acute lumbar radiculopathy improves substantially over six to twelve weeks without surgery, and a meaningful proportion of disc herniations resorb on their own — the immune system treats extruded nucleus material as something to clear. That is the single most useful thing to know early, because it is the reason not to make an irreversible decision in the first weeks unless there is a reason to.

The reason to move faster is deficit. Progressive weakness, a foot drop that is worsening, or any of the cauda equina findings change the calculation completely, because the thing at risk is no longer comfort but function that does not come back. Pain is negotiable. A dying root is not.

What we do about it

Why one person’s disc hurts and another’s does not

Mechanical contact alone is a poor predictor of radicular pain, and this is not a fringe observation — disc protrusions in contact with roots are found routinely in people with no symptoms at all. What makes contact painful is chemistry as much as geometry. Extruded nucleus pulposus is inflammatory in its own right, and the inflammatory response around the root is what sensitizes it.

That inflammatory response is not set to the same gain in everyone. A nerve root has a demanding microcirculation, and chronic hyperinsulinemia impairs microvascular perfusion while systemic metabolic inflammation raises the baseline the local response starts from. In a metabolically inflamed system a smaller mechanical insult produces a larger and longer symptom, and recovery runs slower because the tissue is already in a degradative state.

The third driver is time and sleep. Weeks of severe nerve pain disrupt slow-wave sleep, and short sleep both raises inflammatory tone and lowers descending pain inhibition. That is a loop, and it is why a radiculopathy that is left to run for months so often stops behaving like a compression problem and starts behaving like a sensitization problem — unchanged on imaging, worse in life.

Common questions

What are the first signs of L4-L5 compression?

Typically pain down the outer thigh and shin toward the top of the foot, tingling over the top of the foot and the great toe, and early weakness of toe extension — often noticed as catching a toe on a step rather than as weakness. Any of that which is progressing warrants prompt assessment rather than watchful waiting.

This is set out in Not everything that runs down a leg is sciatica..

Is walking good for nerve pain in the leg?

Generally yes, within tolerance, and it is better than rest for both the nerve and the deconditioning that otherwise follows. If walking reliably produces numbness or weakness that then takes time to clear, that is a different signal and should be assessed.

Your report says herniated disc. So does the report of the person beside you who feels nothing. explains what that looks like.

How painful is a herniated disc?

The honest answer is that it ranges from silent to among the more severe pains in medicine, and the difference is driven more by inflammation and root sensitivity than by the size of the herniation. Which is also why a large herniation on a report is not a prediction of how much someone hurts.

See If your toe is catching on stairs, that is weakness, and weakness is on a clock..

Will I need surgery?

Most people with radiculopathy do not. Surgery has a clear role where there is progressive deficit, cauda equina, or well-localized compression that has failed to settle and is disabling. Where none of those applies, an operation is being asked to solve a problem that is likely to resolve on its own timeline. Before you agree to the operation.

Does an epidural cure it?

It does not resorb the disc. What it does is reduce the inflammation around the root, which frequently reduces the pain enough to let the natural history proceed and to let you move again. Where it works well it also confirms the level, which is worth having.

The detail is in Numbness is information about a level. Where it sits tells us which nerve..

Related reading

• Epidural steroid injection
• Is it actually the disc?
• Sciatica, and what impersonates it
• When back pain is an emergency
• Before you agree to the operation

Not every leg symptom is a nerve root. Piriformis syndrome is a diagnosis of exclusion that gets handed out first.