Bertolotti’s Syndrome and Lumbosacral Transitional Vertebrae: What Your MRI Report Means

A lumbosacral transitional vertebra is a common variation in the way the lowest lumbar bone connects to the sacrum, and it only becomes “Bertolotti’s syndrome” when that anatomy is believed to be contributing to symptoms.

In my practice, I tell patients that a transitional vertebra is first an anatomy finding. The harder question is whether it is actually the pain generator.

This finding is not a tumor. It is not a fracture. It is usually not an emergency. But it can make your MRI report sound confusing, especially if the report uses words like “sacralization,” “lumbarization,” or “pseudoarticulation.”

Quick Answer: What Is a Lumbosacral Transitional Vertebra?

A lumbosacral transitional vertebra, often shortened to LSTV, is a spine bone that has features of both the lower back and the pelvis area.

The lumbar spine is the lower back part of your spine. The sacrum is the triangle-shaped bone at the base of the spine, between the two sides of the pelvis. A vertebra is one spine bone.

An LSTV happens where the lumbar spine meets the sacrum. In plain language, the lowest lumbar vertebra may look partly “joined” to the sacrum or pelvis. Or the upper sacrum may look more like an extra lumbar vertebra.

Your MRI or X-ray report may use terms such as:

• Sacralization of L5
• Lumbarization of S1
• Transitional anatomy
• Pseudoarticulation
• Enlarged transverse process
• Castellvi classification

A transverse process is the small side wing of a vertebra. A pseudoarticulation means a false or extra joint-like contact between bones. The Castellvi classification is a radiology system used to describe the shape and amount of connection in a transitional vertebra.

Many people have this anatomy and never know it. It may be found only because an MRI or X-ray was done for back pain, hip-region pain, or another reason.

Sacralization vs. Lumbarization

Sacralization means the lowest lumbar vertebra, usually called L5, behaves more like part of the sacrum.

Lumbarization means the top part of the sacrum, usually called S1, behaves more like an extra lumbar vertebra.

These terms can also create numbering confusion. In a typical spine, doctors label the lower back bones L1 through L5. With transitional anatomy, it can be harder to decide which level should be called L5-S1, L4-5, or another name.

This matters most before a spinal injection or surgery.

What Is Bertolotti’s Syndrome?

Bertolotti’s syndrome is not just the imaging finding.

It refers to low back, buttock, hip-region, or sometimes leg symptoms that are thought to be related to a lumbosacral transitional vertebra.

In some people, the enlarged side wing of the lowest lumbar vertebra forms an abnormal joint-like connection with the sacrum or the pelvis. This is the pseudoarticulation. Like other joints, this area can sometimes become irritated, inflamed, or arthritic. Arthritic means the joint has wear, inflammation, or painful change.

Symptoms can also come from extra stress at the level above the transitional vertebra. That level may move more because the transitional level moves less.

The Important Distinction: Finding vs. Syndrome

A lumbosacral transitional vertebra is something we see on imaging. Bertolotti’s syndrome is a clinical diagnosis, meaning the imaging finding has to fit the patient’s pain pattern and exam.

A clinical diagnosis means the diagnosis is based on the full picture, not just one MRI sentence. It includes your symptoms, physical exam, imaging, and sometimes your response to a targeted injection.

What Does It Look Like on MRI or X-Ray?

An LSTV can be seen on X-ray, CT, or MRI.

An X-ray is a picture of bones made with a small amount of radiation. A CT scan, or computed tomography scan, is a more detailed X-ray test that shows bone shape well. An MRI, or magnetic resonance imaging scan, uses a magnet to show discs, nerves, joints, and soft tissues.

MRI may show the transitional anatomy. But X-rays or CT can sometimes show the bony connection more clearly.

MRI is still very useful. It can show related issues such as:

• Disc degeneration, which means aging, drying, or wear in the cushion between spine bones
• Nerve compression, which means pressure on a nerve
• Facet arthritis, which means wear or inflammation in the small joints in the back of the spine
• Foraminal narrowing, which means less room in the opening where a nerve exits the spine
• Edema, which means swelling or extra fluid signal, near a pseudo-joint when visible

What I look for on MRI is not just the transitional bone shape. I also look at what is happening around it: the disc above, the nerve openings, the facet joints, and any signs of irritation near the pseudo-joint.

You may find it helpful to read more about how to read your spine MRI report if your report uses several terms at once.

Why Spine Level Numbering Matters

Transitional anatomy can make it difficult to know whether a disc should be labeled L4-5, L5-S1, or another level.

This is not always because someone made a mistake. It can happen because the anatomy itself is harder to count.

Accurate numbering matters most before injections or surgery. If a procedure is planned, the care team needs to be confident everyone is talking about the same spinal level.

Before any injection or operation, I want to be very confident we are all talking about the same spinal level. Transitional anatomy is one of the classic reasons level numbering can become confusing.

Radiologists and surgeons may use several tools to confirm levels, such as:

• Whole-spine imaging
• Counting ribs
• Comparing old reports
• Reviewing X-rays
• Looking at CT scans when bone detail is needed

Does a Transitional Vertebra Cause Pain?

Sometimes yes. Often no.

A transitional vertebra is common in people who have no symptoms from it. The MRI finding matters more when your pain location, physical exam, and imaging all point to the same area.

If LSTV is related to pain, possible pain sources include:

• The pseudoarticulation between an enlarged transverse process and the sacrum or ilium
• The disc above the transitional vertebra
• The facet joints above or across from the transitional side
• The sacroiliac-region structures
• Nerve irritation from altered anatomy or foraminal narrowing

The ilium is the large wing-shaped bone of the pelvis. The sacroiliac joint, or SI joint, is the joint where the sacrum meets the pelvis. Sacroiliac-region pain can overlap with symptoms from Bertolotti’s syndrome. You can read more about sacroiliac joint dysfunction.

The finding matters most when the patient’s pain pattern points to the same side and same region as the abnormal joint or the stressed level above it.

Typical Symptom Patterns

Symptoms that may be seen with Bertolotti’s syndrome include:

• Low back pain, often on one side
• Buttock pain
• Pain near the sacroiliac joint region
• Pain near the beltline
• Pain worse with standing, extension, activity, or certain positions
• Leg pain, numbness, or tingling if a nerve is involved

These symptoms are not specific to Bertolotti’s syndrome.

Similar symptoms can come from a disc herniation, which means a disc bulge or tear that can press on a nerve. They can also come from facet arthropathy, foraminal narrowing, hip problems, spinal stenosis, or sacroiliac joint pain.

Spinal stenosis means narrowing around the nerves in the spine. Sciatica means pain that travels down the leg from irritation of a spinal nerve. If your main symptom is leg pain, you may also want to read about sciatica.

Why Your MRI Report May Sound Confusing

Different radiologists may use different words for the same anatomy.

One report may say “partial sacralization of L5.” Another may say “transitional lumbosacral anatomy.” Another may mention “pseudoarticulation” or “Castellvi type II.”

Some reports describe the anatomy without saying whether it is painful. That is common. Imaging can show structure. It cannot always prove the pain source by itself.

The report may also use different level numbering than a prior report. For example, one report may call a disc L4-5, while another calls the same area L5-S1. This can happen when transitional anatomy is present.

This is one of those MRI findings where the words can sound more alarming than the finding usually is.

How Doctors Decide Whether It Is Clinically Important

Doctors decide whether the finding is important by looking for correlation. Correlation means the pieces fit together.

The key pieces include:

• Where your pain is located
• What movements make it better or worse
• Your neurologic exam
• MRI, X-ray, or CT findings
• Your response to non-surgical care
• Sometimes your response to targeted injections

A neurologic exam checks nerve function. It may include strength, reflexes, sensation, balance, and signs of nerve irritation.

A diagnostic injection is an injection used to test a suspected pain source. It often includes numbing medicine. Sometimes it includes steroid medicine, which is used to calm inflammation. An injection may target the pseudoarticulation, sacroiliac joint, facet joint, or a nerve root.

A nerve root is the part of a spinal nerve as it leaves the spine.

A diagnostic injection can support or weaken a suspected pain source. It does not always prove the diagnosis by itself.

What a Spine Surgeon Looks For

When I review a case with transitional anatomy, I am asking several questions:

• Is the pain one-sided and near the transitional joint?
• Is there degeneration at the level above?
• Is there nerve compression?
• Are the symptoms more consistent with SI joint pain, disc pain, facet pain, or radiculopathy?
• Has the correct spinal level been identified?

Radiculopathy means pain, numbness, tingling, or weakness from an irritated spinal nerve.

This is why Bertolotti’s syndrome is not usually diagnosed from the MRI wording alone. The MRI report is one part of the puzzle.

Treatment Options: Usually Stepwise, Not Automatic Surgery

Most people start with non-surgical care.

Treatment options may include:

• Activity changes
• Anti-inflammatory medication if medically appropriate
• Physical therapy
• Targeted injections in selected cases

Anti-inflammatory medication means medicine used to reduce inflammation and pain. These medicines are not safe for everyone, especially some people with kidney disease, stomach ulcers, blood thinner use, or certain heart risks.

Physical therapy means guided exercise and movement training. For suspected Bertolotti’s syndrome, therapy often focuses on the core, hips, pelvis, and movement patterns.

In my practice, surgery is not the starting point for most patients with suspected Bertolotti’s syndrome. The first job is to prove, as best we can, where the pain is actually coming from.

If the disc above the transitional segment is a major concern, the discussion may overlap with lumbar degenerative disc disease.

When Surgery Is Considered

Surgery is uncommon for Bertolotti’s syndrome.

It may be discussed when symptoms are persistent, disabling, and strongly linked to the transitional segment after a careful workup.

Surgical options described in medical studies include:

• Resection of a painful pseudoarticulation
• Fusion in selected cases

Resection means removing the painful extra bone or joint-like connection. Fusion means joining two or more bones so they heal together as one solid segment.

The correct operation depends on the true pain generator. If the pain is mainly from the pseudo-joint, that is a different problem than pain from the disc above, a nerve, or the sacroiliac joint.

Surgery has been reported to help selected patients, but outcomes vary. It should not be viewed as routine or guaranteed.

When This Finding Is Less Likely to Be the Main Problem

A transitional vertebra is less likely to be the main pain source when your symptoms clearly match another finding.

Examples include:

• A large disc herniation that matches leg pain
• Severe central canal stenosis, which means marked narrowing of the main nerve passage in the spine
• Severe foraminal narrowing that matches a specific nerve pattern
• A fracture
• Infection
• Tumor
• An inflammatory condition

An inflammatory condition means a disorder where the immune system or body inflammation affects joints, bones, or tissues.

The transitional vertebra may also be less important if there is no pain near that area. It may be incidental. Incidental means found on imaging but not clearly causing symptoms.

It is also less likely to explain symptoms that are widespread and do not match one focal spine pain source.

When to Seek Urgent Medical Care

Seek urgent medical care now if you have new loss of bladder or bowel control, numbness in the groin or saddle area, rapidly worsening leg weakness, fever with severe back pain, unexplained weight loss with worsening pain, recent major trauma, or severe pain with a known history of cancer or infection risk. Bertolotti’s syndrome itself is usually not an emergency, but these symptoms can signal other serious spine conditions.

What to Do If Your Report Mentions Bertolotti’s Syndrome or Transitional Anatomy

First, do not panic.

A lumbosacral transitional vertebra is usually a developmental anatomy variation. It may have been there for many years. It does not automatically mean it is the cause of your pain.

Helpful next steps include:

• Write down where your pain is located.
• Note what makes it better or worse.
• Compare the report wording with your actual symptoms.
• Ask whether the finding seems incidental or clinically relevant.
• If injections or surgery are being considered, confirm accurate spinal level numbering.
• If different doctors have given different explanations, consider a written MRI/case review.

FAQ

Is a lumbosacral transitional vertebra serious?

Usually, no. A lumbosacral transitional vertebra is a common developmental variation in the lower spine. Many people have it and never have symptoms from it.

It becomes more important if your pain pattern, exam, and imaging all point to that area.

Is Bertolotti’s syndrome the same thing as having a transitional vertebra?

No. A transitional vertebra is the anatomy seen on imaging.

Bertolotti’s syndrome means that anatomy is believed to be contributing to symptoms. The MRI finding alone does not always prove the syndrome.

Can Bertolotti’s syndrome cause sciatica?

Sometimes it can be linked with radiating leg symptoms if a nerve is irritated or compressed.

But sciatica has many other causes, including disc herniation, foraminal narrowing, and spinal stenosis. The pain pattern and MRI findings need to match.

What does sacralization of L5 mean?

Sacralization of L5 means the lowest lumbar vertebra partly behaves like part of the sacrum.

It may be partly joined to the sacrum or pelvis. It can also make spine level numbering harder.

What does lumbarization of S1 mean?

Lumbarization of S1 means the top part of the sacrum partly behaves like an extra lumbar vertebra.

This is another form of transitional anatomy. It may or may not be related to pain.

Can a transitional vertebra make MRI level numbering confusing?

Yes. Transitional anatomy can make it harder to label the exact spinal levels.

This matters most before injections or surgery. The team may need to compare MRI with X-rays, CT, prior reports, or whole-spine images.

How do doctors know if the transitional vertebra is causing my pain?

They look for a match between your pain location, exam, and imaging.

Sometimes a targeted diagnostic injection is used to test whether the pseudoarticulation, sacroiliac joint, facet joint, or nerve root is the likely pain source.

Do I need surgery for Bertolotti’s syndrome?

Most people do not start with surgery.

Surgery is reserved for carefully selected cases where symptoms are persistent, disabling, and strongly linked to a specific pain generator.

Can physical therapy help Bertolotti’s syndrome?

Physical therapy may help some people by improving core strength, hip motion, pelvic mechanics, and movement patterns.

It does not change the bone shape. The goal is to reduce stress on painful areas and improve function.

Should I get a second opinion if my MRI mentions transitional anatomy?

A second review can be helpful if the report is confusing, if level numbering differs between reports, or if injections or surgery are being discussed.

The main question is not just “Do I have transitional anatomy?” The better question is, “Does this finding fit my symptoms?”

Related Articles

References

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