How Spondylolisthesis Is Diagnosed

Diagnosis is the match between what you feel, what the examination shows, and what the images show. A crack or a slip can be described with some care. That description still does not prove the finding is the cause of pain, and it does not prove the level is unstable.

What the history is for

The visit starts with the story. The same film can belong to a person in pain and a person who is not. The American Academy of Orthopaedic Surgeons says many people with spondylolysis or a slip have no symptoms.

The finding may appear on an X-ray taken for something else. The first job of the history is to learn whether there is a symptom at all.

Spondylolysis is a weakness or stress fracture in the pars interarticularis, the thin bridge of bone between the upper and lower facet joints. Facet joints are the small paired joints at the back of a vertebra, one of the bones of the spine. Spondylolisthesis is the forward shift of a vertebra on the one below it. In the setting that page describes, the shift happens after the pars separates. The history is where a clinician hears which of those words might fit, before any grade is discussed.

When symptoms are present, low back pain is the common one. It may feel like a muscle strain, spread to the buttocks and the back of the thighs, worsen with activity, and ease with rest. A clinician will ask what you were doing, whether a sport repeatedly bends the back backward, and whether the pain is new or long-standing. Those are different situations on the same page.

A slip can add muscle spasm, stiffness, tight hamstrings, and trouble standing and walking. Hamstrings are the muscles along the back of the thigh. Spasm means muscles tighten and guard.

Severe or high-grade slips may include tingling, numbness, or weakness from pressure on a nerve root, a nerve leaving the spine toward the leg. High grade means more than 50 percent of the width of the vertebra has slipped forward. If nerve symptoms are in the story, they belong in plain words.

Where does the tingling go? Does a leg give way? Has walking become hard?

The history is also where an older adult’s problem stays separate from a teenager’s. Worn discs and facet joints, often discussed with a narrow canal, are the usual question in an older adult. A pars stress fracture is often the question in a growing athlete.

Age does not assign the type. The story tells the clinician which images to read against which problem. That split is explained in Spondylolisthesis in Younger People and Older Adults.

Two adult trials show why the label has to be specific. They are not a way to diagnose a child. Försth and colleagues studied adults with lumbar spinal stenosis, narrowing around the nerves, including people with and without a degenerative slip. At 2 years, a disability score did not differ significantly between decompression plus fusion and decompression alone.

Ghogawala and colleagues studied a smaller group with grade I degenerative slips and stenosis. Adding fusion was associated with a larger physical-function gain at 2 years and fewer reoperations over 4 years, without a significant difference on the disability score. A teenager’s pars crack is not that diagnosis.

What the examination checks

The academy describes the examination as a look at tenderness, motion, spasm, weakness, posture, and gait, the way you walk. Tenderness is pain when a spot is pressed. Motion is whether bending reproduces the symptom. Weakness is tested in the legs, because a pressed nerve root can make a muscle give way.

Hamstring tightness is part of the picture the academy describes when a slip is symptomatic, along with stiffness and trouble standing and walking. A tight hamstring on exam is a finding. It is not proof of a slip.

Tight hamstrings occur without any shift of a vertebra. They matter more when they sit next to the story and, later, the film.

The exam cannot see the pars. It can show whether the history appears in the room and whether a nerve root seems involved. Normal strength on one afternoon does not erase a history of the leg giving way.

An abnormal exam does not name the level. Imaging does that after the story has given it something to explain.

Back pain that stays in the back, with a normal walk, is a different report from tingling down one leg. The academy ties nerve symptoms, when they occur, to severe or high-grade slips. It does not say every slip will cause them. Writing down their absence is useful.

X-rays for the crack, the alignment, and motion

The academy says X-rays from several angles look for the crack and for the alignment. A standing side-view X-ray is the film used to judge alignment, with the spine loaded as it is when you are upright. The side view is where the forward shift is compared with the width of the vertebra.

One view can miss the crack. That is why more than one angle is used.

Flexion-extension views are X-rays taken while you bend forward and while you bend backward. Flexion is the forward bend. Extension is the backward bend. They are added when the question is whether the slip changes with motion. A slip on one standing film is a position. A change between the bending films is motion. Those are different facts. The word spondylolisthesis on a report has not shown that the level is unstable. In this conversation, unstable means the alignment changes in a way that matters to care. It does not mean every slip earns the word by existing.

A clear crack supports spondylolysis. If the vertebra has also shifted, the combination supports an isthmic slip. Isthmic means the shift followed the separation in the pars.

If the films show a shift and the pars is not the part that has separated, the type may be degenerative, from worn discs and joints. The rest of the workup then looks at those joints, the disc, and the nerves, rather than at a recent stress fracture. The overview of the types is in What Is Spondylolisthesis?.

Periodic X-rays are how clinicians check whether a vertebra is changing position. A single film cannot show change. Two comparable films can.

They still cannot show why a person hurts. A slip can look the same and still be painful, or increase and still be painless.

The defect is most often in the fifth lumbar vertebra, sometimes the fourth, on one side or both. The report should say which bone and which side. The level is what makes a nerve plausible, if a nerve is involved at all.

CT and MRI answer different questions

CT, computed tomography, shows bone detail. It can make a pars defect easier to see than a plain X-ray. The academy notes that CT uses more radiation, so it is not a routine test. Not routine means it is chosen when bone detail would change the reading, not added as a standard package with every X-ray. A child should not be sent for CT only because a pars crack is on a list of possible causes. The history, the exam, and plain films come first.

MRI, magnetic resonance imaging, shows the discs, the nerves, and sometimes an early pars injury before an X-ray does. Early means a stress injury in the bone that has not yet become a line a plain film can see. MRI is the test that asks whether a slip, or a worn level, is crowding a nerve. That is the question that connects many older adults’ films to lumbar stenosis. A narrow canal on MRI still has to match the walking story. The picture of narrowing is not the diagnosis by itself.

Many people are diagnosed with X-rays when the question is alignment and a visible crack. MRI is added for nerve symptoms or a possible early stress injury. CT is added when the bone is still unclear and the detail is worth the radiation. None of the three proves that a finding hurts.

Försth’s patients had lumbar stenosis, some with a degenerative slip. Ghogawala’s patients all had grade I degenerative spondylolisthesis and stenosis. Grade I is that trial’s label for a smaller slip, not a percent given here, and not a pars line found by chance. How a narrow canal is weighed with a slip is discussed in Spondylolisthesis and Spinal Stenosis Together.

A percent of slip is not a pain score

Clinicians often describe the forward shift as a share of the width of the vertebra. That Meyerding-style description is a measurement of distance. The number the academy attaches to a high-grade slip is more than 50 percent of that width.

High-grade slips, the page says, are more likely to cause significant pain and nerve injury and to be considered for surgery. The page also discusses nonsurgical care for most patients with spondylolysis and low-grade spondylolisthesis. Low-grade is the page’s name for slips it sets apart from that high-grade group. This article does not add percentage bands the academy page does not give.

Grade I, the label in the Ghogawala trial, is a smaller degenerative slip in adults who also had lumbar stenosis. It is not a synonym for high grade. It is not a grade of pars fracture in a teenager.

A high-grade isthmic slip and a grade I degenerative slip can both be called spondylolisthesis. The percent, or the grade name, does not make them one condition.

The percent does not move just because pain moves. A person can feel better while the measurement stays the same, or hurt with a small shift if a nerve is irritated. The academy’s “more likely” line about high-grade slips is a tendency, not a pain score, and not a rule that a high-grade slip must be fused.

A finding on a scan done for something else

A crack or a slip discovered on a scan ordered for another reason is a real finding and an incomplete diagnosis. The academy’s description includes people who have the finding and no symptoms. In that situation the image has not explained a pain, because there may be no pain to explain.

The finding can still be named correctly, as spondylolysis or as a slip of a stated amount. It can still be followed if the person is growing, or if there is a reason to ask whether the position is changing.

The academy says the crack can occur in up to 5 percent of children, as young as age 6, with no known injury. That number is about the bone finding in children. It is not a pain rate, and it is not a number about degenerative slips.

An incidental crack is still named. It is not automatically the cause of a symptom that started somewhere else.

A pars crack at the edge of an X-ray does not win the explanation if the exam points to a hip or to a walking problem that might be a narrow canal. The other direction matters too. Activity-related pain, tight hamstrings, and a pars defect on the film make a coherent story.

The scan answered a suspicion. It did not create one. Repeated extension, as in gymnastics, football, or weightlifting, can contribute, and the crack can also occur without sports.

A sport makes the question reasonable. The film, read against the exam, is what confirms it.

Before the visit, write down when the pain started, what activity is involved, what eases it, and whether the legs are involved. Bring the images if you have them, not only the word grade from a portal message. Ask which type the films show, whether bending views were done, and whether any nerve pressure is being claimed from symptoms or only from a sentence on the report.

A short list of questions for that conversation keeps the finding and a treatment from being decided in the same breath. The list is not a diagnosis. It does not mean a slip has qualified anyone for an operation.

The workup is finished when three lines agree, or when they honestly do not. The story says what life is like. The exam says whether that story shows up in the room.

The images say whether a crack, a shift, or a crowded nerve could explain it. If the images are the only line that speaks, the diagnosis is not done. It has found something to compare.