Could Your Lower Back Pain Actually Be Coming From the SI Joint?

When people develop lower back pain, they often assume the problem must be a disc, pinched nerve, or arthritis in the lumbar spine.

But there is another common source of pain that can easily be overlooked: the sacroiliac joint, or SI joint.

Research suggests that the SI joint may be responsible for approximately 15–30% of chronic, non-radicular lower back pain, meaning that in some groups, roughly 1 out of every 4 patients with persistent lower back pain may actually have pain arising from the SI joint.

At Molina Spine, identifying the true source of pain is one of the most important parts of developing an effective treatment plan.

What Is the SI Joint?

You have two sacroiliac joints—one on each side of the pelvis.

The SI joints connect the sacrum, which is the triangular bone at the bottom of the spine, to the ilium, which forms part of the pelvis.

These joints play an important role in transferring forces between your spine, pelvis, and legs.

Unlike the hip or knee, the SI joint normally moves only a small amount. However, irritation, degeneration, inflammation, abnormal motion, or changes in the mechanics around the joint can produce significant pain.

What Does SI Joint Pain Feel Like?

SI joint pain is often felt in the lower back or upper buttock.

Patients commonly point to an area just below and slightly to the side of the belt line.

Symptoms may include:

• Pain on one side of the lower back

• Buttock pain

• Pain near the back of the pelvis

• Pain when standing from a chair

• Pain after prolonged sitting

• Pain with prolonged standing

• Pain when walking

• Pain when climbing stairs

• Pain when rolling over in bed

• Pain when getting in or out of a car

• Discomfort when putting weight primarily on one leg

Although SI joint pain often stays around the lower back and buttock, it can sometimes refer into the thigh or farther down the leg, which can make it resemble sciatica.

Why Is SI Joint Pain Frequently Missed?

One of the challenges with SI joint pain is that its symptoms overlap with many other causes of lower back pain.

A patient may have an MRI showing:

• Degenerative discs

• Disc bulges

• Facet arthritis

• Mild spinal stenosis

But an abnormality on an MRI does not automatically mean that abnormality is causing the patient's pain.

Many people have age-related changes on imaging without significant symptoms.

That is why we focus on finding the pain generator rather than simply treating what appears abnormal on an MRI.

The SI joint should remain part of the differential diagnosis when evaluating persistent mechanical lower back and buttock pain. Multiple studies have estimated that it accounts for approximately 15–30% of chronic low back pain in selected populations.

What Causes SI Joint Pain?

There is not always one obvious cause.

SI joint pain may develop following:

• A fall

• Motor vehicle accident

• Repetitive stress

• Heavy lifting

• Pregnancy

• Changes in walking mechanics

• Hip problems

• Leg-length differences

• Arthritis or degeneration

• Previous lumbar spine surgery

Previous spine surgery, particularly procedures that alter the mechanics of the lower lumbar spine and pelvis, has also been associated with SI joint pain.

Sometimes the symptoms develop gradually without a specific injury.

How Do We Diagnose SI Joint Pain?

There is no single MRI finding that always proves the SI joint is the source of pain.

Diagnosis often starts with a detailed history and physical examination.

During the examination, your physician may perform several SI joint provocative maneuvers that place stress across the joint.

When multiple tests reproduce the patient's typical pain, suspicion for the SI joint increases.

However, physical examination findings are only one part of the evaluation.

Diagnostic SI Joint Injection

One of the most useful ways to determine whether the SI joint is contributing to a patient's symptoms is an image-guided diagnostic SI joint injection.

Using imaging guidance, a needle is carefully positioned into the SI joint.

A small amount of anesthetic medication is injected.

The important question is simple:

Did your usual pain significantly improve after the joint was numbed?

If the patient's typical pain improves substantially for the expected duration of the local anesthetic, that response provides additional evidence that the SI joint is an important pain generator.

This is why injections can sometimes be valuable not only as a treatment, but also as a diagnostic tool.

Can an SI Joint Injection Treat the Pain?

Yes.

An SI joint injection may contain both local anesthetic and an anti-inflammatory corticosteroid.

The anesthetic can provide short-term relief while also helping with diagnosis, while the steroid may decrease inflammation within the joint and provide longer-lasting improvement.

The amount and duration of relief vary from patient to patient.

What Happens If the Pain Comes Back?

Treatment depends on the cause and severity of the symptoms.

Options may include:

• Activity modification

• Physical therapy

• Pelvic and core stabilization exercises

• Anti-inflammatory medication when appropriate

• Image-guided SI joint injections

• Other interventional treatments

• SI joint fusion in carefully selected patients

Surgery is not the first treatment for most patients with SI joint pain.

However, patients who have persistent symptoms, convincing examination findings, and significant temporary improvement following diagnostic SI joint injections may sometimes be evaluated for a minimally invasive SI joint fusion.

SI Joint Pain vs. Sciatica

These two conditions can sometimes feel similar, but they are not the same thing.

Sciatica generally refers to pain caused by irritation or compression of a spinal nerve, often from conditions such as a herniated disc or lumbar spinal stenosis.

SI joint pain originates from the joint connecting the sacrum to the pelvis.

Sciatica is more likely to produce neurological symptoms such as:

• Numbness

• Tingling

• Weakness

• Pain following a specific nerve distribution

SI joint pain more commonly produces localized lower-back, pelvic, or buttock pain, although referral into the leg is possible.

A careful examination can help differentiate between the two.

Don't Assume Every Lower Back Problem Is Coming From Your Lumbar Spine

One of the most important lessons in treating back pain is that the location of the pain does not always identify its source.

Hip arthritis can look like spinal disease.

Facet pain can resemble disc pain.

And SI joint pain can look remarkably similar to a lumbar spine problem.

With the SI joint potentially accounting for roughly one-quarter of chronic low back pain in some patient populations, it is a diagnosis that should not be overlooked.

At Molina Spine, our goal is to identify the actual pain generator and then choose the most appropriate and least invasive treatment for that particular problem.

If you have persistent lower back or buttock pain and previous treatments have not provided relief, the SI joint may be worth evaluating.

Domingo Molina IV, MD, FAAOS
Orthopaedic Spine Surgeon
Molinaspine.com

This information is intended for general educational purposes and does not replace an individualized medical evaluation.