Gonstead Pelvic Analysis

At a time when many chiropractors focused primarily on upper cervical subluxations, Dr. Clarence Gonstead created the foundation concept around the pelvis, starting with the femoral heads as the foundation of the spine. He may have been the first to recognize that the sacroiliac (SI) joints move in specific directions and can become fixed.

Although we often refer to these ilia findings as “subluxations,” SI joint dysfunction does not create direct nerve interference in the same way a spinal subluxation can. However, a misaligned or fixed sacroiliac joint can create compensatory changes throughout the spine. Over time, these compensations may contribute to abnormal loading of the spinal joints and discs, accelerating conditions such as degenerative disc disease, degenerative joint disease, and osteoarthritis.

Gonstead performed an extensive study of the pelvis and developed several key concepts that remain the basis of Gonstead pelvic analysis today. We’ll deal with the Ilia and the Sacrum, the bones that make up the SI joint.

The Ilia

X-Axis Rotation (PI and AS)

Using the Posterior Inferior Iliac Spine (PSIS) as the primary reference point, the ilium can rotate around the X-axis in one of two directions:

• Posterior Inferior (PI). This causes the length of the innominate to appear longer on x-ray.
• Anterior Superior (AS) This causes the length of the innominate to appear shorter on x-ray.

So rotation in either direction changes the apparent size of the innominate measurement on the AP pelvis X-ray.

These rotations also affect the appearance of the obturator foramen.

• An PI ilium generally produces a longer diagonally appearing obturator foramen.
• An AS ilium generally produces a smaller diagonally appearing obturator foramen.

The bone itself is not actually changing length. Instead, the apparent change is caused by X-ray magnification. Structures farther away from the Bucky (image receptor) appear larger, while structures closer or more in line with the central ray appear smaller.

A simple way to understand this is by placing your hand near a wall with a flashlight shining on it. As you move your hand farther from the wall, the shadow becomes noticeably larger, even though your hand has not changed size. The same magnification principle applies to pelvic x-rays.

Y-Axis Rotation (IN and EX)

The ilium may also rotate around the Y-axis.

• Internal rotation (IN) causes the width of the ilium to appear wider on x-ray.
• External rotation (EX) causes the width of the ilium to appear narrower on x-ray.

These rotations also affect the appearance of the obturator foramen.

• An EX ilium generally produces a larger appearing obturator foramen on x-ray.
• An IN ilium generally produces a smaller appearing obturator foramen on x-ray.

Static Palpation

With static palpation, we are primarily evaluating for inflammation and tenderness.

• A PI ilium will generally demonstrate more inflammation along the superior portion of the sacroiliac joint.
• An AS ilium will generally demonstrate more inflammation near the inferior portion of the joint.
• An EX ilium, because the posterior SI joint opens slightly, will demonstrate inflammation along the posterior aspect of the sacroiliac joint.
• An IN ilium tends to create irritation more anteriorly within the joint. Since this area cannot be directly palpated, patients may instead report groin pain on the involved side.

X-Ray Example

In this case, the patient has misalignments of AS2In9 on the left and equally and oppositely PIEx on the Right. The Sacrum is rotated posteriorly on the left by 2mm so the listing is P2-R.

Motion Palpation

Restricted motion is the major indicator of SI joint dysfunction.

Motion palpation helps determine whether a radiographic finding is actually clinically significant. If the joint is moving, generally it is not necessary to adjust.

The PI/AS can be determined by raising the knee in a standing position.

• A PI ilium will generally demonstrate more restriction moving AS.
• An AS ilium will generally demonstrate more restriction moving PI.

The Ex/In by Ab/Ad-duction of the thighs in the seated position.

• An EX ilium will have more restriction when Abducting the thighs.
• An IN ilium will have more restriction when Adducting the thighs.

Visual Observation

The pelvis can also be evaluated visually.

Observe the gluteal folds (the crease at the bottom of the butt cheek) and overall gluteal width.

• A lower gluteal fold generally indicates a PI ilium.
• A higher gluteal fold generally indicates an AS ilium.
• A more prominent buttock generally indicates an EX ilium.
• A flatter buttock generally indicates an IN ilium.

These are helpful observations but should always be confirmed through palpation and radiographic analysis.

Compound Listings

Most Gonstead pelvic listings are compound listings, meaning the ilium rotates around both the X-axis and Y-axis simultaneously.

For example:

Left PI 4 EX 3

This indicates that the left ilium has rotated:

• 4 mm Posterior Inferior
• 3 mm Externally

The millimeter values represent the measured difference between the left and right sides.

KEY POINT: The ilia move in equal and opposite directions. If the left ilium rotates Posterior Inferior and External, the right ilium rotates Anterior Superior and Internal.

Clinically, PI and EX commonly occur together, while AS and IN also commonly occur together.

Leg Length

PI ilia often create the appearance of a shorter leg on the involved side because the femoral head sits lower.

AS ilia often create the appearance of a longer leg.

Again, apparent leg length inequality does not necessarily identify the primary problem.

A lower lumbar or sacral subluxation may cause the body to compensate by raising or lowering the femoral head in an effort to maintain balance and stability.

The Sacrum – The Other Part of the SI Joint

The Sacrum is the other part of the of the SacroIliac joint. The base (articulation with lowest lumbar) of the sacrum may move straight Posteriorly, or Posterior on the Right or Left. A P sacrum is confirmed the lateral x-ray. Clearly it will be P to the L5.

The sacrum may also only move P on either side. The P side will have a longer measurement from the S1 tubercle to the lateral edge comparing one side to another on x-ray.

A Spondy

A Spondylolisthesis pretty much mimics a P sacrum. We set the P sacrum under the L5. See our videos to understand this adjustment.

When Would We Adjust the Ilium vs Lumbar or Sacrum?

If there is an instrument break, we look to the lumbar or sacrum since that can cause direct nerve pressure. An ilium itself generally does not create direct nerve pressure, but correcting a fixated ilium may reduce mechanical stress throughout the sacrum and lower lumbar spine.

For example, suppose a patient repeatedly presents with an L5 subluxation that does not hold well after adjustment. If examination reveals a fixated left PIEx ilium, correcting the ilium may remove the underlying mechanical stress contributing to the recurring L5 problem. Also, a patient may present with lower back complaints without an instrumentation break. In those cases, evaluating the sacroiliac joints becomes especially important.

Do we adjust the Sacrum or Ilium?

Every person is different; however, there are basic guidelines we use.

In the Gonstead system, we are always adjusting Posterior to Anterior with a few exceptions including extremities, the atlas, occiput, and coccyx. But in the pelvis, everything will be adjusted P to A. Note: An AS ilium is still adjusted P to A, just the inferior aspect of the joint.

So if there is an instrument break at L5/S1 and a BP (Base Posterior Sacrum), I’d start there. If there is a break and no BP and a posteriorly rotated sacrum, depending on other factors like the Ilium listing, spinal rotation, curvature, I may adjust a posteriorly rotated sacrum.

Again, with no instrumentation break but misaligned pelvis, without any additional considerations I may adjust the SI joint.

The basic rule would be with a break, either adjust a BP sacrum, a P rotated sacrum, or a lowest lumbar.

Again every patient is different.

It’s important to note to that radiographic misalignment alone is never an indication for adjustment.

Here are some example adjustments:

ASIn Ilium Push

PIEx Ilium Pull/Push

ASEx Ilium Pull

(much more difficult adjustment)

Don’t Adjust Compensations (the rule before you need to break it)

Many apparent pelvic misalignments are compensatory. Frequently, a lower lumbar or sacral subluxation causes the ilium to assume an altered position. In these cases, adjusting the ilium first may be inappropriate because it is not the primary problem.

Because the sacrum directly articulates with the ilium through the sacroiliac joint, sacral dysfunction frequently contributes to pelvic findings. For this reason, the sacrum often requires correction before the ilium.

Clinical Integration

No single finding should determine whether an adjustment is made. The Gonstead system use five criteria including

• Instrumentation
• Static palpation
• Motion palpation
• Visual observation
• Full-spine radiographic analysis

When all of these findings correlate, you can determine with much greater confidence what should be adjusted.

Ultimately, years of practice wisdom may override any of the “rules” especially if the results are not coming as expected. But as Gonstead admonished about not getting results, to “check you application, don’t question the principle.”

One great advantage we have. Chiropractic is a practice, which is why you can get results at one chiropractor and not another. Because we’re using the best available criteria to determine what to do that’s been proven for over a century of Gonstead, we are really good. If we can’t figure out something right away, as the possibilities of what could be the subluxation get less and less, the patient eventually gets better.