A disc bulge on an MRI feels like an answer. For most people with sciatica it isn't.
You know the sensation. The burning, electric, shooting pain that starts somewhere in the lower back or deep in the buttock and travels down the leg. Sometimes into the calf. Sometimes all the way to the foot. Sometimes with numbness or tingling that makes you wonder whether something serious is happening.
You've been told it's your disc. Maybe a scan confirmed some degree of bulge or herniation at L4-L5 or L5-S1. You've been given stretches, anti-inflammatories, a referral to physio, maybe a cortisone injection that helped for a few weeks before wearing off.
And the sciatica keeps returning.
Here's what the disc-first explanation misses and why so many people with sciatica stay in the cycle longer than they need to.
What sciatica actually is
Sciatica is not a diagnosis. It is a description of a symptom pattern: pain, numbness, or tingling that follows the distribution of the sciatic nerve down the leg. The nerve is being irritated or compressed somewhere along its path, and that irritation is producing the characteristic referred sensation.
The standard assumption is that the compression is at the disc. A disc bulge pressing on a nerve root at the lumbar spine is one cause of sciatic pain. It is not the only cause, and it is frequently not the primary driver even when a disc finding shows up on imaging.
This distinction matters enormously because the location of the compression determines everything about what needs to happen to resolve it. Treating the lumbar disc for a problem that is originating at the piriformis, which is one of the most common clinical scenarios we see, addresses the wrong structure entirely.
The piriformis problem that explains most of what the disc doesn't
The sciatic nerve in most people passes directly beneath the piriformis muscle, a deep hip rotator that sits behind the hip joint in the posterior buttock. In a significant proportion of people it passes through the muscle itself.
When the piriformis is in chronic spasm or becomes hypertonic, which happens as a downstream consequence of dysfunctional gait mechanics, it compresses the sciatic nerve at that location and produces symptoms that are clinically indistinguishable from disc-generated sciatica. Same pain distribution. Same referral pattern down the leg. Same aggravation with sitting. Completely different cause.
This matters because the treatment for piriformis-driven sciatic pain is not spinal. It is hip. And if you have been doing lumbar traction, lumbar stabilisation exercises, and lumbar mobilisation for a problem that is originating at the piriformis in the posterior hip, you have been working on the wrong part of the system for the entirety of your treatment.
The reason this gets missed is straightforward. The presenting symptom is leg pain. The MRI shows a disc finding. The disc gets treated. The piriformis, which is not on the standard imaging protocol for sciatica and is not assessed in standard lumbar physiotherapy, continues to compress the nerve. The symptoms continue.
Why the disc finding can be misleading
Disc bulges and herniations are common findings on lumbar MRI in the general population. Research consistently shows that a substantial proportion of people with disc findings on imaging have no symptoms whatsoever. The presence of a disc finding does not automatically mean the disc is the source of the sciatic pain.
What a disc finding does indicate is that the disc has been under load. Discs bulge when they are compressed and loaded in directions they aren't designed to handle, which is exactly what happens when movement patterns place chronic load on the lumbar spine. The disc finding is often a downstream consequence of the same movement dysfunction that's driving the piriformis compression and the nerve irritation.
Treating the disc without addressing the movement pattern that loaded it to the point of bulging is treating the output while the input continues unchanged.
What's actually driving the nerve compression
Restricted hip extension in gait
This is the most consistently identified upstream driver of piriformis-driven sciatica at FP Brisbane. When the hip cannot extend properly during the push-off phase of walking, the gluteal muscles fail to fire effectively through that phase. The piriformis compensates. It takes on load it was not designed to carry, develops chronic tension, and compresses the sciatic nerve at its passage beneath it.
This happens across thousands of steps every day. The piriformis is not being stressed by any single event. It is being chronically overloaded by a gait pattern that has been running without hip extension for months or years.
Stretching the piriformis releases its tension temporarily. The same gait pattern reloads it within hours. The sciatic symptoms return. The cycle continues until the gait pattern changes.
Anterior pelvic tilt
A forward-tilted pelvis increases the lumbar curve and changes the loading environment of both the lumbar discs and the piriformis. It alters the position of the piriformis relative to the sciatic nerve and changes the angles at which the hip rotators are required to work through the gait cycle. Both effects increase sciatic nerve irritation risk through different mechanisms operating simultaneously.
Sitting mechanics and disc loading
Prolonged sitting in a posteriorly tilted position loads the lumbar discs in the direction most likely to produce posterior bulging. Hours of daily sitting in a slumped position applies sustained posterior load to the discs across every working day. This is not a disc problem. It is a load management problem that produces a disc finding as its consequence.
Old injuries not fully resolved
An ankle sprain, a knee injury, a hip issue from years earlier, each of these can alter gait in ways that change how the hip loads and rotates through the stride cycle. The piriformis sits at the end of that mechanical chain. Unresolved restrictions anywhere in the lower limb have a direct influence on what happens at the piriformis and through it, on the sciatic nerve.
The sciatica presentation often begins months or years after the original injury. The connection is never made because nobody has assessed the gait pattern that links them.
Why sciatica keeps coming back after treatment
Sciatica that settles with rest and returns with activity is almost always a pattern problem. The rest reduces the load on the irritated nerve below the threshold of symptoms. The return to normal activity reloads the same gait pattern, compresses the same nerve at the same location, and produces the same symptoms.
The disc didn't re-bulge because you went for a walk. The piriformis returned to its chronic tension state because the movement pattern driving it was never addressed. The cycle continues at exactly the speed the movement pattern reasserts itself.
What surgery does and doesn't address
Discectomy removes the portion of disc material pressing on the nerve root. When the compression is genuinely discal and significant, this produces real and meaningful relief. But surgery removes the structural consequence of the loading pattern. It does not change the loading pattern itself.
This is why post-surgical sciatica recurrence rates are meaningful. The same pattern applied to the same or adjacent disc levels over time can reproduce the same finding. The disc was the output of the pattern. Surgery addressed the output. The pattern continues.
At FP Brisbane we see post-surgical sciatica presentations regularly. The nerve is no longer being compressed by the original disc. It is being compressed at the piriformis by a gait pattern that was present before the surgery and is present after it because nobody addressed it.
Client result: "I'd had sciatica for two years. I'd had physio, cortisone injections, and was being told I should consider surgery for an L5-S1 disc bulge. At FP Brisbane the assessment found a significant hip extension restriction on the right side and a piriformis that was clearly in chronic tension on the same side. There was nothing wrong with the disc that correcting the movement pattern wouldn't address. Four months of gait-based corrective work and the sciatica has resolved completely. I cancelled the surgical consultation." Brisbane client
What this looks like at Functional Patterns Brisbane
At FP Brisbane, sciatica assessment starts with the gait pattern, not the scan. We look at what the hip is doing through the push-off phase, where the piriformis is being loaded, what the pelvic mechanics look like through the stride cycle, and what the overall pattern of load distribution tells us about where the nerve compression is originating.
From that assessment we build a corrective program that addresses the mechanical source of the nerve compression rather than the nerve itself or the disc that may or may not be contributing to it.
If your sciatica keeps returning, or if you have been told surgery is the next step, it is worth having the movement pattern properly assessed first. The answer is very often not where anyone has been looking.
Frequently Asked Questions — Sciatica Root Cause
Is sciatica always caused by a disc bulge?
No. Sciatic nerve compression at the piriformis muscle in the posterior hip produces symptoms that are clinically indistinguishable from disc-generated sciatica. Piriformis-driven sciatica is one of the most commonly missed diagnoses in lower back and leg pain presentations, partly because standard lumbar imaging does not assess the piriformis and standard lumbar physiotherapy does not address it.
Why does my sciatica keep coming back after it settles?
Because rest reduces the load on the irritated nerve without changing the movement pattern that's producing the compression. When activity resumes, the same gait pattern reloads the same structure at the same location. The nerve compression returns. Lasting resolution requires identifying and correcting the movement pattern driving the compression, not managing the symptoms through repeated cycles of rest and return.
Can sciatica be treated without surgery?
Yes, in most cases. Surgery is appropriate when the nerve compression is significant, the disc finding is clearly the source, and conservative management has genuinely failed. In many sciatica presentations, the disc is either not the primary source of compression or is a secondary finding produced by the same movement dysfunction that is driving piriformis compression. Addressing the movement pattern that is producing the nerve compression produces lasting resolution without surgical intervention in the majority of cases we see.
What does gait have to do with sciatica?
Gait mechanics directly influence the tension state of the piriformis through hip extension in the push-off phase. When the hip doesn't extend adequately in gait, the piriformis compensates and becomes chronically overloaded. Across ten thousand daily steps this chronic overload produces sustained sciatic nerve compression at the piriformis. This is the most consistently identified driver of piriformis-driven sciatica at FP Brisbane and the finding most consistently missed in standard sciatica management.