Recurring sciatica is common, and it rarely means you need an operation. Here are the reasons it happens and what actually helps.
Have you been troubled with sciatica, pain radiating from your back down your leg, which improves after a few days or a couple of weeks and then keeps returning?
It is a frustrating pattern, and a common one. Let me explain why it happens.
First, the disc
The commonest cause of sciatica is a herniated disc compressing a nerve.
Your spine is a stack of bones called vertebrae, with a cushion between each pair. Those cushions are the discs.
In cross-section, a disc has a central substance called the nucleus, with a consistency very similar to crab meat, as the textbooks tend to put it. Around it is an outer lining, the annulus, made of layer upon layer of fabric holding the disc in place.
That lining can wear thin and tear until a fragment of the nucleus herniates outwards and pinches the nerve. This causes inflammation around the nerve, and because those nerves supply the muscles of the leg, you get pain shooting down the leg, sometimes with numbness.
Why the first episode settles
When the tear first happens, inflammatory material also leaks out of the disc. This fluid effectively stings the nerve, and it accounts for the majority of the pain.
With time the outer lining heals and scars over, and the pain settles, even though there may still be compression present. Nerves tolerate a certain amount of compression perfectly well.
Why it comes back: four reasons
1. The bulge catches the nerve again. If the disc continues to bulge, then every so often certain movements will pinch that nerve a little more, causing bruising around it and a recurrence of pain.
2. Scar tissue is weaker than the original. Where the nucleus has broken free of the annulus entirely, the body’s natural response is to break it down, reabsorb it, and lay down scar tissue around the annulus.
The annulus is made of collagen. In its undamaged form it is highly organised, arranged in layers. Scar tissue collagen is not as robust and is often thinner, making it prone to tearing again, with new fragments bulging out.
3. Sometimes there is no compression at all. If the lining is weak, we do not even need the nucleus to pinch the nerve. The tear alone can allow inflammatory fluid to leak out, and that stinging of the nerve produces recurrent sciatic pain with no actual compression present.
4. Foraminal stenosis. The nerves leave the spine through openings called foramina. That opening can narrow, either from a disc herniating in that exact location, or from flattening of the disc, or thickening of the ligaments or the joints at the back of the spine.
Weight-bearing tends to make this worse. It is a fairly common finding with age, and nerves tolerate it, so you may be unaware anything is happening. But every so often the nerve gets bruised inside the foramen and you get a recurring episode.
A fifth: the facet joint
The arch at the back of the spine has a joint either side, the facet joint, connecting each arch with the ones above and below.
This joint contains fluid within a capsule. That capsule can thicken, the surrounding ligaments can thicken, and in combination they can compress the nerve. Occasionally a cyst forms, which can do the same.
Swelling, inflammation and bruising in that segment can recur with repetitive strain, giving you recurring episodes of sciatica.
“Surely if it keeps coming back, I need an operation?”
This is the natural conclusion, and usually the wrong one.
The operation in question is a microdiscectomy, where under the microscope we shave away the offending fragment of disc. It is not indicated between episodes of pain.
Here is why. If the disc is not large and is not causing much compression, we will not achieve a great deal, but we will introduce risk. To remove the fragment we must open the annulus, making a hole in it, and that alone carries a small risk of recurrent herniation.
And if the scan shows the disc has already healed over, operating will not necessarily prevent it herniating again at some point in the future. All it does is add risk: potential damage to the nerve, infection, and the other risks of spinal surgery.
When surgery is indicated
- Persistent pain lasting weeks without improving on conservative measures
- Neurological deficits, such as foot or ankle weakness that is progressing
- Cauda equina syndrome, where you have difficulty passing urine, or pain and weakness down both legs with numbness around the genital region. This is a critical emergency.
What actually helps
I strongly advise anyone with back pain or sciatica to get into the habit of regular exercise, and within that programme to include exercises that strengthen the muscles supporting and surrounding the spine.
The logic is mechanical. Those muscles give additional support to the annulus, the lining of the disc, and that extra support helps prevent tears in it.
It is not an absolute guarantee. Some people who keep up these exercises will still have the odd recurrence. But overall it reduces how often episodes happen.
The key takeaway
Recurring sciatica usually reflects a healed but weakened disc lining, not a problem that needs cutting out.
The exceptions are persistent pain that will not settle, progressive weakness, and cauda equina symptoms. Short of those, building strength around the spine does more for you than an operation would.
