Why Does My Sciatica Come and Go? Causes and Relief

Sciatica comes and goes primarily because the factors driving it are themselves dynamic: inflammation around a compressed nerve flares and subsides, herniated disc material can physically shrink over time, and everyday variables like posture, activity level, and even stress shift the amount of irritation a nerve root experiences on any given day. The waxing-and-waning pattern frustrates people who expect a structural problem to produce constant pain, but the biology behind sciatica is far more fluid than most realize.

Pain Without Pressure, Pressure Without Pain

The conventional picture of sciatica is a bulging disc squeezing a nerve, like stepping on a garden hose. That mechanical story is part of the truth, but animal experiments have shown something surprising: nucleus pulposus, the jelly-like core of a spinal disc, can cause nerve damage and pain even without physically compressing the nerve at all. When disc material leaks into the epidural space, substances on the surface of its cells trigger an inflammatory cascade. Tumor necrosis factor-alpha (TNF-α) appears to be the main chemical culprit, capable of slowing nerve conduction and causing nerve fiber degeneration on its own.¹

This chemical component explains a lot about why sciatica fluctuates. Inflammation is not a fixed state. It ramps up and settles down in response to immune-cell activity, local blood flow, and external triggers. On days when the inflammatory environment around a nerve root is relatively calm, you feel fine. On days when something stirs it up again, the pain returns, sometimes with startling intensity, even though nothing has changed structurally in your spine. TNF-α and related signaling molecules are central to this on-again, off-again cycle.²

Herniated Discs Can Shrink on Their Own

One of the most underappreciated reasons sciatica improves is that the herniated disc material causing the trouble often physically shrinks without surgery. This process, called spontaneous resorption, happens when the body mounts an immune response against the displaced disc tissue. New blood vessels grow into the herniated fragment, macrophages infiltrate and start breaking it down, and enzymes degrade the disc’s structural matrix. Over weeks to months, the protruding material gets smaller or disappears entirely.³

This is not a rare outcome. A systematic review covering over 2,000 patients found that roughly three-quarters of herniated discs showed spontaneous resorption after conservative treatment, with rates across individual studies ranging from 20% to over 96%.⁴ The more dramatically a disc has herniated, the more robust the immune response tends to be, and paradoxically, larger herniations sometimes resorb faster than smaller ones. The relief from resorption correlates with reduced nerve root compression and less radicular pain.⁵

Resorption does not happen overnight, though, and it does not proceed in a straight line. During the weeks or months it takes, pain can retreat and then return as the inflammatory and immune processes fluctuate. This is one reason someone might feel nearly normal for a stretch and then have a bad week: the disc fragment is still partially there, and minor provocations can re-irritate the nerve before resorption finishes the job.

What Actually Triggers a Flare-Up

If sciatica is simmering at a low level, certain activities and conditions can push it into a full flare. A longitudinal study of people experiencing acute low back pain episodes found that prolonged sitting of more than six hours was the single strongest physical trigger, roughly quadrupling the odds of a flare-up. Stress and depression also independently raised flare-up risk by nearly threefold. Interestingly, physical therapy sessions were associated with lower odds of a flare.⁶

The sitting connection makes mechanical sense. Prolonged sitting increases intradiscal pressure and can press a herniated fragment more firmly against a nerve root. But the stress and depression finding points to something less obvious. Psychological distress does not just change how you perceive pain; it can amplify inflammatory signaling and muscle tension in ways that worsen the physical problem. This creates a frustrating feedback loop: pain causes stress, stress lowers your threshold for pain, and both make the next flare more likely.

Lifestyle Factors That Keep Sciatica Returning

Beyond day-to-day triggers, certain longer-term patterns increase both the likelihood of developing sciatica and the chances of it recurring. A 15-year longitudinal study found that being overweight or obese, being physically inactive, and smoking were all independently associated with sciatica. The effect sizes for weight alone were modest, suggesting that excess body fat is not the whole story. But the researchers noted a plausible mechanism: fat tissue secretes pro-inflammatory molecules, including TNF-α, the same chemical implicated in nerve root irritation from disc material. Chronic low-grade inflammation from excess adipose tissue may keep the nerve environment primed for flare-ups.⁷

Smoking adds its own damage. Nicotine impairs blood flow to spinal discs, which already have a limited blood supply, and accelerates disc degeneration. Physical inactivity weakens the deep spinal muscles that stabilize your lumbar spine, making it easier for a disc to shift under load. Each of these factors is individually modest, but they compound. A sedentary, overweight smoker has a meaningfully different risk profile for recurring sciatica than someone who maintains a healthy weight and stays active.

Why Your MRI May Not Tell the Whole Story

People often assume that if a scan shows a disc herniation, the herniation is the source of their pain, and that as the herniation resolves, pain should resolve with it. The relationship is far messier than that. A study published in the New England Journal of Medicine followed sciatica patients for a year and found that about 84% reported a favorable outcome. But here is the striking part: whether or not a disc herniation was still visible on MRI at one year had no meaningful relationship to whether the patient felt better. Among patients with a good outcome, 35% still showed a herniation on imaging. Among those with a poor outcome, 33% still showed one. The MRI could not distinguish the two groups.⁸

This disconnect reinforces the idea that structural findings are only part of the picture. Inflammation, nerve sensitization, and the chemical environment around the nerve root matter at least as much as what the disc physically looks like. It also means that chasing imaging findings with repeat scans can be misleading. If your pain is improving, the fact that an MRI still shows some bulging does not mean the improvement is an illusion or that another flare is inevitable.

When the Problem Is Not Actually a Disc

Not everything that feels like sciatica comes from a lumbar disc. Several other conditions produce pain radiating down the back of the leg, and some of them have their own reasons for coming and going.

Piriformis syndrome occurs when the piriformis, a small muscle deep in the buttock, compresses or irritates the sciatic nerve as it passes nearby. The symptoms closely mimic those of lumbar radiculopathy: buttock pain radiating down the leg, sometimes with numbness or tingling.⁹ Because piriformis tightness can fluctuate with activity, posture, and muscle tension, the pain from this condition tends to be especially intermittent. Sitting on a wallet, driving for long periods, or running can all aggravate it, while stretching or rest lets it settle down.¹⁰

Degenerative lumbar spinal stenosis is another common mimic, especially in older adults. As the spinal canal narrows with age, the nerves inside get crowded. Pain, numbness, or weakness typically worsens with walking or standing and improves with sitting or bending forward, a pattern called neurogenic claudication. This position-dependent quality makes the symptoms inherently intermittent: you feel it when you walk through a grocery store, then it fades when you sit down. Vascular claudication from poor circulation in the legs can produce a similar pattern, making correct diagnosis more important for this age group.

What Helps During a Flare and Between Episodes

Because sciatica tends to improve on its own over time for most people, the goals of treatment during a flare-up are to manage pain, keep functioning, and avoid doing anything that slows natural recovery. Between flares, the goal shifts to reducing the odds that the next one happens.

Structured exercise programs remain one of the most consistently supported interventions. A study combining McKenzie lumbar extension exercises with transcutaneous electrical nerve stimulation (TENS) found significant improvements in pain levels, range of motion, and disability after six weeks.¹¹ The direction of the exercise matters: extension-based movements aim to centralize the pain, meaning to shift it from the leg back toward the lower back, which often signals that pressure on the nerve is decreasing. Not everyone responds to extension, though. If bending backward makes your leg symptoms worse, a different exercise approach is needed, and a physical therapist can help sort out which direction suits your particular situation.

For severe flares that do not respond to exercise and oral pain medication, epidural steroid injections are a common next step. These deliver corticosteroids directly to the inflamed nerve root area, aiming to dampen the inflammatory response. Systematic reviews have found evidence of short-term pain relief and functional improvement, though the long-term benefit over conservative care is less clear. Injections buy time for natural resorption to proceed and can make it possible to participate in physical therapy when pain is otherwise too intense.

Positional adjustments during the workday also make a difference. Research on standing workers has shown that adjusting body position, such as shifting arm positions during prolonged standing, can reduce the activity of lumbar erector spinae muscles and may help lower back pain.¹² The broader principle is that static postures of any kind are hard on a sensitive spine. Alternating between sitting, standing, and walking throughout the day matters more than finding a single “correct” posture and holding it for hours.

How Much of Recovery Is Just Time

There is a common tendency to credit whatever treatment you were doing when your sciatica improved: the supplements kicked in, the chiropractor fixed it, the new mattress made the difference. But the natural history of sciatica is strongly tilted toward improvement regardless of intervention. A meta-analysis of conservative treatments for chronic non-specific low back pain estimated that roughly half of the overall treatment effect seen in clinical trials was attributable to natural changes over time, rather than to the specific treatment or placebo effects.¹³ This does not mean treatments are useless. The specific treatment effects were real, accounting for about a third of pain improvement. But it does mean that much of the recovery people experience would have happened anyway, driven by processes like disc resorption and the settling of inflammation.

Knowing this is actually useful. It means that if your sciatica is improving slowly, the natural trajectory is working in your favor and patience is a legitimate strategy, not a failure to act. It also means that expensive or risky interventions deserve scrutiny: is this likely to speed things up meaningfully beyond what time alone will accomplish?

When Surgery Enters the Picture

Most people with sciatica from a herniated disc will never need surgery. But for those with severe or progressive neurological deficits, like significant weakness in the foot or leg, or loss of bladder and bowel control, surgery becomes more urgent. For everyone else, surgery is usually considered after conservative treatment has failed to provide adequate relief over a period of months.

Discectomy, the surgical removal of the herniated disc fragment pressing on the nerve, is the most common procedure. Recovery is generally good, but it is not a guaranteed permanent fix. A review of surgical outcomes noted that a significant number of patients report symptom recurrence after discectomy. Factors associated with less favorable outcomes after surgery include smoking, female sex, older age, and lower socioeconomic status. One encouraging finding is that the duration of symptoms before surgery does not appear to strongly affect long-term outcomes, though operating within the first year may lead to faster initial recovery.¹⁴

The recurrence of sciatica after surgery is worth highlighting because it is something people rarely hear about before the operation. When a piece of disc is removed, the remaining disc can re-herniate at the same level, or a different disc can develop problems. Surgery addresses the current mechanical issue but does not change the underlying tendency for disc degeneration. This is another reason sciatica can come and go even after surgical treatment.

The Human Spine Was Not Designed for This

Stepping back from individual flare-ups, there is a broader reason disc herniations are so common in humans. Research into the evolutionary anatomy of the spine has found that certain vertebral body shapes, specifically rounder ones with shorter pedicles, are associated with a higher risk of disc herniation. These shapes resemble the vertebrae of our primate relatives more closely than the typical human form. Walking upright places enormous axial loads on the lower spine, and vertebrae that are less well adapted to those loads may provide less structural support during bipedal posture and movement.¹⁵

In practical terms, this means disc problems are not a sign that you did something wrong. They are a consequence of a skeleton that is still, in evolutionary terms, adapting to upright walking. Some people inherit vertebral shapes that handle the load well; others inherit shapes that are more vulnerable. This genetic variability partly explains why two people with similar lifestyles can have very different experiences with sciatica, and why the condition runs in some families.