Condition · Lumbar spine
Bertolotti Syndrome
An enlarged side process on the lowest lumbar vertebra, partly joined to the sacrum from birth. In most people it never causes a symptom; in some, it becomes a one-sided source of low back pain.
Symptoms
Bertolotti syndrome describes pain coming from a lumbosacral transitional vertebra — a lowest lumbar vertebra, usually L5, whose side process (the transverse process) is enlarged and forms a partial, extra joint with the sacrum or the pelvis. The anatomy is present from birth; the pain, when it comes, usually arrives anywhere from the teens to the forties. The classic pattern is one-sided low back pain, felt just off the midline over the back of the pelvis, sometimes aching into the buttock on the same side. Because the transitional segment moves less than a normal level, the disc and joints directly above it — and sometimes the opposite side — absorb extra stress, so pain can also develop one level up. Just as important: many people have this anatomy and never hurt at all, which is why a transitional vertebra on an X-ray is the starting point of a conversation, not its conclusion.
Diagnosis
Standing X-rays show the enlarged transverse process and the partial joint it forms; classification systems (Castellvi) grade how complete the connection is, from a merely enlarged process to a full bony bridge to the sacrum. MRI looks at the disc above the transitional level and excludes other pain sources, while CT shows the partial joint itself most clearly. The harder question is attribution. Transitional anatomy is common and usually silent, so the examination pattern, the imaging, and — when the answer would change treatment — a diagnostic injection into the partial joint all have to point the same way. Dr. Choi refers to pain management colleagues for such injections rather than performing them himself. Strong but temporary relief while the joint is numbed supports it as the pain source; no relief argues against treating it.
What your first visit covers
A first visit for suspected Bertolotti syndrome starts with the pain pattern: one-sided or midline, how long it has been present, what positions and activities drive it, and what has already been tried. Examination checks the low back, the hips, and the sacroiliac joints — SI joint pain is the great mimic here and sits inches away — along with strength, reflexes, and sensation to exclude nerve involvement. Your imaging is reviewed for the transitional anatomy itself and for wear at the level above it. Most patients leave with a non-surgical plan and a clear statement of what would have to be true before the transitional segment itself is treated as the culprit.
Treatment options
Most Bertolotti syndrome is managed without surgery: activity modification, medication during flares, and a conditioning program that strengthens the trunk and hips. Physical therapy also addresses the transitional segment's neighbors — the level above it and the SI joint and hip share its load, and they often need the attention. Injections into the partial joint, performed by pain management colleagues on referral, play a dual role: they can calm an arthritic pseudo-joint for a time, and their response is the best available test of whether that joint is generating the pain in the first place.
When surgery is considered
Surgery for Bertolotti syndrome is uncommon and deliberately selective. Two operations exist: removing the enlarged transverse process and its partial joint (resection), or fusing the transitional segment so it can no longer move. Surgery is considered only when the pain pattern fits, a diagnostic injection has confirmed the joint as the source, and a genuine trial of conservative care has failed. Patients deserve to hear that the published evidence is small case series rather than large trials — which is exactly why the confirmation step matters so much before anyone operates.
When a second opinion can help
The most common reason for a second opinion here is a fusion recommended on the strength of an X-ray alone. Transitional anatomy shows up in a sizable minority of all spines and most of it is innocent. If the confirmatory steps have not been done — a matching examination, a serious look at the SI joint and the level above, and ideally a diagnostic injection — it is reasonable to ask what else could be generating one-sided pain before committing to an operation on an anatomical variant.
When to seek care promptly
Seek prompt evaluation for pain that follows a significant injury, pain with fever, unexplained weight loss accompanying new back pain, or any new leg weakness or change in bladder or bowel function. Those patterns suggest something other than transitional anatomy and should not wait for a routine appointment.
Frequently asked questions
What is Bertolotti syndrome?
Bertolotti syndrome is pain attributed to a lumbosacral transitional vertebra: the lowest lumbar vertebra (L5) has an enlarged side process that forms a partial extra joint with the sacrum or pelvis. The anatomy is a variation present from birth, named for the Italian physician Mario Bertolotti, who described it in 1917. It becomes a syndrome only when that partial joint — or the stressed level just above it — actually generates pain. In most people who have the anatomy, it never does.
How common is a transitional vertebra?
Common. Depending on how strictly it is defined, studies find transitional anatomy in roughly one in ten to one in five adults, making it one of the most frequent anatomical variants in the lumbar spine. That frequency is exactly why finding it on an X-ray proves so little on its own: a finding shared by millions of pain-free people needs more than its presence on a scan before it is named the cause of one person's pain.
How do you know Bertolotti syndrome is causing my pain?
By convergence. The pain pattern should fit — typically one-sided, low, and near the partial joint. The imaging should show the transitional anatomy without offering a better explanation. Competing sources, especially the SI joint and the disc above the transitional level, should be assessed. And when the answer would change treatment, a diagnostic injection into the partial joint is the strongest test: substantial relief while the joint is numbed supports it as the source. Dr. Choi refers to pain management colleagues for these injections.
Does Bertolotti syndrome need surgery?
Usually not. Most cases are managed with activity modification, a conditioning program, medication during flares, and time. Surgery is reserved for the minority with a confirmed source, a matching pain pattern, and a genuine failure of conservative care. Because the anatomy is so common and so often innocent, the burden of proof sits on anyone proposing to operate on it — and that proof is achievable, but it has to be earned case by case.
What surgery is done for Bertolotti syndrome?
Two operations exist. Resection removes the enlarged side process and its partial joint, preserving motion at the segment. Fusion eliminates the segment's motion by joining the transitional vertebra to the sacrum. Resection suits a patient whose pain comes from the partial joint itself; fusion enters the discussion when the segment or the level above is also unstable or badly worn. The published evidence is small case series rather than large trials, which is why patient selection carries the outcome.
Can Bertolotti syndrome cause pain on one side only?
Yes — one-sided pain is the classic presentation, because the transitional anatomy is usually asymmetric: one side forms the partial joint while the other side remains a normal joint, so the abnormal stresses concentrate on one side. The same asymmetry loads the opposite facet joint and the disc above unevenly, which is why pain can also appear at the level above the transitional segment or, less often, seem to switch sides.
Related care
SI joint dysfunction · Degenerative disc disease · Spondylolisthesis · SI joint fusion
From Back Talk
Related reading: Bertolotti Syndrome, Explained · 5 Non-Surgical Options to Try Before Spine Surgery
Care pathway
Minimally invasive surgeryEndoscopic visualizationDr. Jihoon ChoiRockwall · Garland · Forney · Greenville
Initial consultation or second opinion?
Meet Dr. Jihoon Choi to find out whether your transitional anatomy is actually generating your one-sided back pain — and if it is, what the honest options are, from conditioning to the rare case for operating on it. Call (972) 817-7450 or request a visit online.