Sciatica: What’s Actually Causing the Nerve Irritation?

Last week, we looked at the difference between sciatica and piriformis syndrome. Both can create similar symptoms that travel through the hip and down the leg, but the source of the irritation is different. With sciatica, the problem begins higher up, at one or more of the nerve roots that eventually contribute to the sciatic nerve. This separates it from irritation occurring farther along the nerve, such as in piriformis syndrome.

Not every case of sciatica begins with a mechanical positioning problem. Age-related degenerative changes, inflammatory processes, injury, and other structural conditions can contribute to irritation or compression of a nerve root. But when we’re looking at sciatica through a mechanical lens, another question becomes important: what chronic positions and muscular relationships may be contributing to the irritation?

The lumbar spine is part of a larger system that includes the pelvis and hips. To understand how chronic positioning may affect a lumbar nerve root, we first need to look at the relationship between them.

How Pelvic Position Influences the Lumbar Spine

The pelvis and lumbar spine don’t exist independently of one another. Changes in pelvic position can influence the orientation of the lumbar spine, while limitations at the hips may influence the positions available to both. Because of these relationships, chronic pelvic positioning can influence how the lumbar spine is oriented and loaded over time.

This matters because the spaces surrounding the lumbar nerve roots aren’t fixed. The intervertebral foramina change dimensions as the lumbar spine changes position. Flexion generally increases foraminal dimensions, while extension decreases them. Side bending and rotation can also create different conditions from one side of the spine to the other.

These relationships can occur in all three planes and rarely exist in isolation. An anterior pelvic tilt can accompany increased lumbar extension, while a hip hike or lateral pelvic tilt may occur alongside lumbar side bending. Transverse rotation of the pelvis can similarly exist as part of a rotational lumbopelvic position. Someone may demonstrate several of these characteristics at once, creating a three-dimensional pattern rather than a simple anterior tilt, hip hike, or rotation.

This is why we don’t want to treat a pelvic asymmetry as an isolated finding. We want to understand the complete lumbopelvic position and how it relates to the irritated nerve root. If that position may be reducing available space around the nerve root or creating persistent asymmetrical loading through the area, improving those relationships can become part of the plan.

Assessing What Maintains the Position

Once we identify the lumbopelvic position, the next question is what may be maintaining it. Chronic differences in muscle length, tension, strength, or motor control around the hips and trunk can contribute to how the pelvis and lumbar spine are positioned. Hip limitations may also influence which positions are readily available to the system.

This is why identifying a single “tight muscle” or postural deviation rarely gives us the entire answer. We’re looking at the larger pattern and the relationships that may be keeping the body there. Corrective exercise can then target what we actually find, whether that means addressing chronic muscular tension, strengthening an opposing relationship, improving available hip motion, or improving control of a more favorable lumbopelvic position.

Importantly, a position doesn’t have to reproduce someone’s symptoms during a particular exercise before it becomes mechanically relevant. If an already irritated nerve root exists within a chronic lumbopelvic position that may reduce available space or create persistent asymmetrical loading, there may be value in improving that position even if changing it doesn’t immediately provoke or relieve the person’s symptoms.

The goal isn’t to create one universally “correct” posture. It’s to identify mechanical relationships that may be unnecessarily compromising an irritated nerve root and improve the ones we reasonably can.

Addressing Sciatica Mechanically

Sciatica tells us that a nerve root is irritated, but it doesn’t tell us what the entire lumbopelvic system looks like in the individual experiencing it. Looking at chronic positioning and the muscular relationships maintaining it gives us another piece of that picture.

This is why addressing sciatica mechanically isn’t about applying the same stretches or exercises to everyone. We can assess the individual in front of us, identify chronic positions and muscular relationships that may be contributing to the irritation, and address what we actually find.

Next week, we’ll follow the sciatic nerve farther down and look at piriformis syndrome, including the mechanical relationships around the hip and deep gluteal region that may contribute to irritation there.

Want to Learn More

📖 Read this next: Sciatica vs. Piriformis Syndrome: What’s the Difference?

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