What a Postural X-ray Actually Shows (and What It Doesn't)

Written and clinically reviewed by Dr. Jun (Jun Chung): Doctor of Chiropractic (New Zealand College of Chiropractic), NZCC- and ACC-registered, 13+ years' clinical practice. Auckland Wellness Centre, Rosedale and Milford. Last updated: August 2026 · next scheduled review: August 2027.

Quick answer: A postural spinal X-ray measures bone: the angle of your spinal curve in degrees, how far your head sits forward of your shoulders in millimetres, and structural findings such as scoliosis or degenerative change. It does not show discs, nerves, muscle or pain, which is why it is ordered to answer a specific question rather than taken as a matter of routine.

Spinal X-ray is one of the more misunderstood parts of musculoskeletal care. Some clinics image everyone who walks in. Others treat imaging as something to be avoided at all costs. Both positions skip the useful question, which is what the image can actually tell you and whether that answer changes what happens next.

This is what a postural X-ray measures, what it cannot measure, and how we decide whether to order one.

What a postural X-ray measures precisely

Bone shows up on X-ray with high contrast, so anything defined by bone position can be measured rather than estimated. On a lateral cervical film that means:

• The cervical curve, in degrees. Lines are drawn along the vertebral bodies from C2 to C7 and the angle between them is measured. This is the number people mean when they talk about a straight neck or a reversed curve.
• Forward head translation, in millimetres. How far the head sits in front of the shoulders in the sagittal plane, measured against a vertical reference rather than judged by eye.
• Segmental alignment. How individual vertebrae sit relative to the ones above and below, including rotation and translation.
• Structural findings. Scoliosis and its Cobb angle, degenerative change, disc space height, bone spurs, congenital anomalies, old fractures, and the small number of conditions that need referral rather than treatment.

On a lumbar film the same logic applies to the lower back curve, pelvic position and vertebral alignment.

The number depends on how it was measured

This is the part that almost never gets explained, and it matters if you are comparing one clinic's report to another's.

There is more than one accepted way to measure a cervical curve, and they do not produce the same number on the same spine. The Cobb method drawn from C2 to C7 systematically reads a smaller curve than the posterior tangent method: in the study that compared them directly on the same radiographs, the Cobb angle averaged about 17 degrees where the posterior tangent method gave about 26 degrees. Neither is wrong. They are measuring slightly different things.

Two consequences follow. First, a curve angle quoted without the method used is close to meaningless. Second, comparing your before and after films only works if both were measured the same way, by the same convention.

At Auckland Wellness Centre the line drawing follows the Chiropractic BioPhysics protocol and is read against the Harrison spinal model, where average adult cervical lordosis measured by posterior tangents sits at about 34 degrees with a normal spread of roughly 9 degrees either side. Dr. Michael Blandy, one of about six CBP-trained chiropractors in New Zealand, reads the line drawings on your images. Your follow-up film is measured by the same convention as your first, which is the only way a comparison means anything.

What a postural X-ray does not show

X-ray images bone. Soft tissue absorbs radiation at similar rates to the tissue around it, so it does not separate out on a plain film. That rules out a specific and important list:

• Discs. A disc bulge or herniation is soft tissue and does not appear. A film can show reduced disc space height, which suggests degenerative change, but that is an inference and not a diagnosis of herniation. MRI is the imaging for that question.
• Nerves and spinal cord. Nerve root compression cannot be seen or excluded on X-ray.
• Muscle and ligament. Strains, tears and ligament injury are invisible.
• Pain. This is the one worth stating plainly. Imaging findings and symptoms correlate loosely. Plenty of people have textbook films and significant pain, and plenty have unremarkable pain with striking films. An X-ray tells you about structure, not about how much something hurts.

How much radiation is involved

Worth knowing rather than worrying about, and worth asking any clinic that proposes imaging.

A single lateral cervical view is a small fraction of a millisievert, and a full cervical series sits in the region of 0.2 mSv. New Zealand's Office of Radiation Safety puts natural background exposure, which everyone receives from soil, air and food, at about 2 mSv a year. That places a full cervical series at close to five weeks of ordinary background exposure. Real, but modest.

That is not an argument for imaging freely. It is an argument for imaging on a question. Dose accumulates over a lifetime, and an image that cannot change the plan adds exposure and cost without adding information.

When we refer for an X-ray, and when we don't

We refer when: the curve itself is the question and posture photographs cannot answer it; symptoms have not responded to a reasonable course of care; there is a history of significant trauma; neurological findings are present; or a structural condition such as scoliosis is suspected and needs measuring rather than estimating.

We do not refer when: the history and examination already explain the problem; recent imaging is on file and still answers the question; or the result would not change what we do next.

Referral is direct and it is not limited to X-ray. Our chiropractors refer directly for both X-ray and ultrasound, so there is no GP appointment in between and no waiting on a referral letter. Imaging is carried out by an external radiology provider. Where the findings point beyond what we should be treating, we refer you on to a specialist.

Where the X-ray sits in the assessment

Imaging is one input, not the assessment itself. Most of what we record at a first visit comes from the room rather than the radiology provider: a PostureScreen standing capture giving head position in millimetres and shoulder and pelvic level, range of motion measured in degrees on both sides, and orthopaedic and neurological testing. The X-ray is added when a question about the curve or the structure needs answering to a precision that photographs cannot reach.

Whatever is measured is written down and re-measured at set intervals against your own starting numbers, not against an average. The full list of what gets recorded, and in what units, is on our spinal and posture assessment page.

Frequently asked questions

Do I need an X-ray for back or neck pain? Usually not. Most musculoskeletal pain is diagnosed from history and examination, and imaging is added when a specific question needs answering. If a clinic proposes an X-ray, a fair question is what they expect it to show and what they would do differently depending on the result.

Does an X-ray show a slipped disc? No. Discs are soft tissue and do not appear on plain film. An X-ray can show narrowed disc space, which points at degenerative change, but confirming a disc herniation needs MRI.

How much radiation is in a spinal X-ray? A full cervical series is in the region of 0.2 mSv. New Zealand's Office of Radiation Safety puts natural background exposure at about 2 mSv a year, so a cervical series is close to five weeks of it. Modest, but a reason to image on a question rather than by default.

Can a chiropractor refer me for an X-ray in New Zealand? Yes. Our chiropractors refer directly for X-ray and ultrasound, so you do not need to see your GP first. The imaging is done by an external radiology provider.

What is a normal cervical curve? Measured by posterior tangents from C2 to C7, average adult cervical lordosis is around 34 degrees, with a normal spread of roughly 9 degrees either side. Measured by the Cobb method the same spine reads lower, which is why the method has to be stated alongside the number.

Is a postural X-ray covered by ACC? Imaging related to an accepted injury claim is generally covered. Imaging with no injury behind it is charged privately. Our chiropractor lodges the ACC45 at the first visit where a claim applies.

This article is general information, not a diagnosis. Auckland Wellness Centre sees patients at Unit E2, 27 William Pickering Drive, Rosedale (09 600 1939) and 177B Shakespeare Road, Milford (09 281 3687). What we measure at a first visit is set out on our spinal and posture assessment page.