When leg pain from a trapped nerve has gone on long enough, an injection starts to look like the obvious answer. It can be a good decision, and it works best when you know what it is for. A nerve root block is a window of reduced pain, and the size of the benefit depends almost entirely on what happens inside that window.
A nerve root block, also called a transforaminal epidural injection, places local anaesthetic and steroid around a specific nerve root where it leaves the spine. It is done under X-ray or CT guidance so the needle reaches the right level, usually as a day-case procedure taking a few minutes.
It has two possible purposes, and they are worth separating:
The steroid addresses inflammation around the nerve. The disc bulge or bony narrowing that irritated it in the first place is unchanged by the injection, which is why the effect has a time limit attached.
NICE guideline NG59 takes a specific position on spinal injections:
The evidence supporting the recommendation comes from acute presentations, meaning under three months, and NICE notes that repeat injections in that short window are unlikely to be cost effective. That is worth knowing if you are being offered a course of three.
Severity matters as much as duration here. The strongest case is severe, disabling leg pain that is stopping sleep and function, where a period of relief changes what is possible.
Private quotes are built from the same parts as any procedure, and the components to check are:
Ask specifically whether the quote is for one injection or a course, and what the policy is if the first one gives limited relief. Ask too whether the referral is for a diagnostic block or a therapeutic one, because the two have different success criteria and you should know which you are being measured against.
Here is the pattern that plays out repeatedly. The injection works, the leg pain drops substantially within a week or two, life returns to normal, and nothing else changes. Three or four months later the pain comes back, and the conclusion drawn is that the injection wore off.
What that window was for was rehabilitation. The pain-free period is the only time when the movement, strength and load tolerance work can actually be done, because a nerve that hurts at every attempt makes progressive loading impossible.
The work itself is unglamorous: restoring movement in the spine and hip, building the glutes, hamstrings and calf on the affected side where the nerve has caused weakness, rebuilding walking and sitting tolerance in graded steps, and gradually reintroducing bending and lifting with technique that holds up. Six to twelve weeks of that inside the window is what converts temporary relief into a durable change.
A compressed nerve root often leaves measurable weakness behind, most commonly in calf push-off, in the muscles that lift the foot, or in the quadriceps depending on the level involved. That weakness is easy to miss, because it does not hurt and it hides behind compensation.
Testing it properly means single-leg heel raises counted to fatigue against the other side, not a quick push against a hand. A difference of ten or fifteen repetitions between sides is common and entirely fixable, and it is a frequent reason people continue to feel unreliable long after the pain settles.
Progressive weakness, numbness spreading, or any disturbance of bladder or bowel function is different and needs urgent medical assessment the same day. Our sciatica page lists the warning signs in full.
Most sciatica settles without any procedure. The natural history is genuinely favourable, and the majority of disc-related nerve pain improves over weeks to a few months.
What helps in the meantime is staying as active as the pain allows, finding the positions that reduce leg symptoms and using them deliberately, keeping walking going in short frequent bouts, and appropriate pain relief discussed with your GP. Our articles on buttock pain and how to tell it from sciatica and trapped muscle pain cover two problems that regularly get mistaken for nerve pain.
An injection becomes the sensible next step when severe pain is not settling on that trajectory, when sleep and function are badly affected, or when a surgical decision needs the diagnostic information.
The question that comes up most often in the room is a version of "should I just have the injection?" It usually arrives from someone who has spent six weeks unable to sit through the drive down the A26 to Lewes or the A22 towards Eastbourne without the leg lighting up, which for most people around Uckfield means the commute, the shopping and the school run all at once.
The answer turns on what the injection is being asked to do. Where pain is severe enough to block sleep and function, it can be the thing that makes everything else possible, and the case for it is strong. What decides whether the benefit holds is what fills the weeks that follow. Nerve root compression reliably leaves calf and glute weakness on the affected side, and that weakness sits there unnoticed while the pain has everyone’s attention. Testing it against the other side, then rebuilding it during the pain-free window, is the difference between an injection that bought three months and one that changed the picture.
Our sciatica page sets out how the nerve level and the weakness are identified.
How long does a nerve root block last?
Anywhere from a few weeks to several months. The variation is wide, and the rehabilitation done during the relief is a large part of what decides the longer-term outcome.
Does it hurt?
Local anaesthetic is used, so the procedure is uncomfortable rather than painful for most people. A temporary flare in the day or two afterwards is common.
Can I have more than one?
Sometimes, though NICE notes repeat injections within the acute window are unlikely to be cost effective. Repeated steroid also carries its own considerations, which your consultant will explain.
Is it a step towards surgery?
Not necessarily. Many people have one injection, do the rehabilitation and never need anything further. A diagnostic block is sometimes used specifically to inform a surgical decision.
When can I start physiotherapy afterwards?
Usually within a few days, once any post-injection flare has settled. Starting early in the window is the point.
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