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. It only becomes “Bertolotti’s syndrome” when that anatomy is believed to be contributing to symptoms.

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

It is not a tumor, fracture, or emergency. But it can make your MRI report sound confusing, especially with words like “sacralization,” “lumbarization,” or “pseudoarticulation.”

Quick Answer: What Is a Lumbosacral Transitional Vertebra?

A lumbosacral transitional vertebra (LSTV) is a spine bone with features of both the lower back and the pelvis area.

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

An LSTV occurs where the lumbar spine meets the sacrum: 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 is a false or extra joint-like contact between bones. The Castellvi classification is a radiology system for describing the shape and amount of connection in a transitional vertebra.

Many people have this anatomy and never know it, finding out 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 L5, behaves more like part of the sacrum. Lumbarization means the top of the sacrum, usually 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 is 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 Bertolotti’s Syndrome Actually Means

Bertolotti’s syndrome is more than the imaging finding. It refers to low back, buttock, hip-region, or sometimes leg symptoms 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 pelvis — the pseudoarticulation. Like other joints, it can become irritated, inflamed, or arthritic (worn or painfully inflamed).

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

Here is the distinction that matters: a transitional vertebra is something we see on imaging, while Bertolotti’s syndrome is a clinical diagnosis — based on the full picture (symptoms, exam, imaging, and sometimes response to a targeted injection), not one MRI sentence.

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

An LSTV can be seen on X-ray, CT, or MRI. An X-ray shows bone using a small amount of radiation; a CT scan (computed tomography) shows bone shape in more detail; an MRI (magnetic resonance imaging) uses a magnet to show discs, nerves, joints, and soft tissues.

MRI may show the transitional anatomy, though X-ray or CT can sometimes show the bony connection more clearly. MRI is still very useful, because it can show related issues such as:

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

If your report uses several terms at once, it may help to read more about how to read your spine MRI report.

Why Spine Level Numbering Matters

Transitional anatomy can make it hard to know whether a disc should be labeled L4-5, L5-S1, or another level. This is not always someone’s mistake — the anatomy itself is harder to count.

Accurate numbering matters most before injections or surgery — I want everyone certain they are describing the same spinal level. Transitional anatomy is one of the classic reasons numbering gets confusing.

To confirm levels, radiologists and surgeons may use whole-spine imaging, rib counting, comparison with old reports, X-rays, or CT 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 finding matters more when your pain location, exam, and imaging all point to the same area — the same side as the abnormal joint or the stressed level above it.

If LSTV is related to pain, possible 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 (SI joint) is where the sacrum meets the pelvis, and SI-region pain can overlap with symptoms from Bertolotti’s syndrome. You can read more about sacroiliac joint dysfunction.

Typical Symptom Patterns

Symptoms seen with Bertolotti’s syndrome may 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

None of these is specific to Bertolotti’s syndrome. Similar symptoms can come from a disc herniation (a disc bulge or tear that can press on a nerve), facet arthropathy, foraminal narrowing, hip problems, spinal stenosis, or sacroiliac joint pain.

If leg pain is your main symptom, you may also want to read about sciatica — pain that travels down the leg from irritation of a spinal nerve.

Why Your MRI Report May Sound Confusing

Different radiologists may use different words for the same anatomy — “partial sacralization of L5,” “transitional lumbosacral anatomy,” “pseudoarticulation,” or “Castellvi type II.” Many reports describe the anatomy without saying whether it is painful, because imaging shows structure but cannot always prove the pain source by itself.

Here, the words can sound more alarming than the finding usually is.

How Doctors Decide Whether It Is Clinically Important

Doctors decide by looking for correlation — whether the pieces fit together:

• 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 — strength, reflexes, sensation, balance, and signs of nerve irritation.

A diagnostic injection tests a suspected pain source. It often includes numbing medicine and sometimes steroid medicine, which calms inflammation, and 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, but 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:

• Is the pain one-sided and near the transitional joint?
• Is there degeneration at the level above?
• Is there nerve compression?
• Do the symptoms fit 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 rarely diagnosed from MRI wording alone — the report is one part of the puzzle.

Treatment: Stepwise, Not Automatic Surgery

Most people start with non-surgical care. Options may include:

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

Anti-inflammatory medication reduces 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 is guided exercise and movement training. For suspected Bertolotti’s syndrome, it often focuses on the core, hips, pelvis, and movement patterns.

In my practice, the first job is to prove, as best we can, where the pain is actually coming from before considering surgery.

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 — removing the extra bone or joint-like connection — and fusion in selected cases, joining two or more bones so they heal as one solid segment.

The right operation depends on the true pain generator: pain mainly from the pseudo-joint 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 and it should not be viewed as routine or guaranteed.

When It’s Probably Not the Main Problem

A transitional vertebra is less likely to be the main pain source when your symptoms clearly match another finding, such as:

• A large disc herniation that matches leg pain
• Severe central canal stenosis (marked narrowing of the main nerve passage in the spine)
• Severe foraminal narrowing that matches a specific nerve pattern
• A fracture, infection, tumor, or inflammatory condition

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

The transitional vertebra may also be incidental — found on imaging but not clearly causing symptoms — if there is no pain near that area. It is also less likely to explain widespread symptoms that 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.

If Your Report Mentions Transitional Anatomy

First, do not panic. A lumbosacral transitional vertebra is usually a developmental variation that may have been present for years. It does not automatically mean it is causing your pain.

Helpful next steps:

• 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 not. It is a common developmental variation, and many people have it without symptoms. It matters more when your pain pattern, exam, and imaging all point to that area.

Can Bertolotti’s syndrome cause sciatica?

Sometimes, if a nerve is irritated or compressed. But sciatica has many other causes — disc herniation, foraminal narrowing, spinal stenosis — so the pain pattern and MRI findings need to match.

Can physical therapy help?

It may, by improving core strength, hip motion, and pelvic mechanics. Therapy does not change the bone shape; the goal is to reduce stress on painful areas and improve function.

Do I need surgery for Bertolotti’s syndrome?

Most people do not start with surgery. It is reserved for carefully selected cases where symptoms are persistent, disabling, and strongly linked to a specific pain generator.

Should I get a second opinion?

A second review helps if the report is confusing, if level numbering differs between reports, or if injections or surgery are on the table. The real question isn’t whether you have transitional anatomy — it’s whether that finding fits your symptoms.

Related Articles

References

American College of Radiology. (2021). ACR Appropriateness Criteria®: Low Back Pain.

Apazidis, A., Ricart, P. A., Diefenbach, C. M., & Spivak, J. M. (2011). The prevalence of transitional vertebrae in the lumbar spine. The Spine Journal, 11(9), 858–862. https://doi.org/10.1016/j.spinee.2011.08.005

Castellvi, A. E., Goldstein, L. A., & Chan, D. P. K. (1984). Lumbosacral transitional vertebrae and their relationship with lumbar extradural defects. Spine, 9(5), 493–495.

Jancuska, J. M., Spivak, J. M., & Bendo, J. A. (2015). A review of symptomatic lumbosacral transitional vertebrae: Bertolotti’s syndrome. International Journal of Spine Surgery, 9, 42. https://doi.org/10.14444/2042

Konin, G. P., & Walz, D. M. (2010). Lumbosacral transitional vertebrae: classification, imaging findings, and clinical relevance. AJNR American Journal of Neuroradiology, 31(10), 1778–1786. https://doi.org/10.3174/ajnr.A2036

Luoma, K., Vehmas, T., Raininko, R., Luukkonen, R., & Riihimäki, H. (2004). Lumbosacral transitional vertebra: relation to disc degeneration and low back pain. Spine, 29(2), 200–205.

Marks, R. C., & Thulbourne, T. (1991). Infiltration of anomalous lumbosacral articulations: steroid and anesthetic injections in 10 back-pain patients. Acta Orthopaedica Scandinavica, 62(2), 139–141.

Nardo, L., Alizai, H., Virayavanich, W., et al. (2012). Lumbosacral transitional vertebrae: association with low back pain. Radiology, 265(2), 497–503. https://doi.org/10.1148/radiol.12112747

Qaseem, A., Wilt, T. J., McLean, R. M., Forciea, M. A., & Clinical Guidelines Committee of the American College of Physicians. (2017). Noninvasive treatments for acute, subacute, and chronic low back pain: A clinical practice guideline from the American College of Physicians. Annals of Internal Medicine, 166(7), 514–530. https://doi.org/10.7326/M16-2367

Santavirta, S., Tallroth, K., Ylinen, P., & Suoranta, H. (1993). Surgical treatment of Bertolotti’s syndrome: follow-up of 16 patients. Archives of Orthopaedic and Trauma Surgery, 112(2), 82–87.