Sacroiliitis: Inflammation of the Joint Connecting Your Spine and Pelvis
If you have deep pain in the lower back, buttock, or hip that worsens with standing or climbing stairs, the cause may be Sacroiliitis inflammation of the sacroiliac (SI) joint, where the spine meets the pelvis.
Because SI joint pain can mimic hip or lumbar spine issues, precise diagnosis is essential.
What Is the Sacroiliac Joint?
The sacroiliac joints sit on either side of the spine, connecting the sacrum
(the base of your spine) to the iliac bones of your pelvis.
These joints play a vital role in:
Transferring weight between the upper body and legs
Providing stability during walking or standing
Absorbing shock from movement
When irritated or inflamed, they can produce deep, localized pain that may radiate to the buttock or thigh.
What Causes Sacroiliitis
Arthritis or joint wear (degenerative sacroiliitis)
Inflammatory disease (such as ankylosing spondylitis)
Injury or trauma (falls, car accidents)
Pregnancy and childbirth (ligament stretching and pelvic stress)
Uneven leg length or posture imbalance
Previous lumbar fusion or surgery increasing SI joint load
Common Symptoms
Sacroiliitis can cause pain patterns often confused with sciatica or hip disorders. Typical features include:
Deep aching pain in the lower back, buttock, or hip (often one-sided)
Pain that worsens with standing, stair climbing, or sitting for long periods
Discomfort rolling over in bed or getting out of a car
Occasional radiation of pain into the thigh (but rarely below the knee)
Common Symptoms
Sacroiliitis can cause pain patterns often confused with sciatica or hip disorders. Typical features include:
Deep aching pain in the lower back, buttock, or hip (often one-sided)
Pain that worsens with standing, stair climbing, or sitting for long periods
Discomfort rolling over in bed or getting out of a car
Occasional radiation of pain into the thigh (but rarely below the knee)
How It’s Diagnosed
Because SI joint pain can mimic other spine or hip problems, accurate diagnosis requires
a combination of clinical assessment and image-guided testing
Physical Examination
Special tests that stress the SI joint (e.g., FABER, Gaenslen, or compression tests) reproduce pain when the joint is inflamed.
Imaging
X-rays or MRI: reveal inflammation, arthritis, or joint changes.
CT Scan: may show bone irregularities or ankylosis in chronic cases.
Diagnostic Nerve Block
An image-guided SI joint injection with numbing medication remains the gold standard for confirming the diagnosis—if the pain temporarily disappears, the joint is the source.
Risk Factors
Women during or after pregnancy
Individuals with prior lumbar fusion
People with autoimmune or inflammatory conditions
Athletes or laborers with repetitive pelvic stress
Those with leg length differences or scoliosis
Risk Factors
Women during or after pregnancy
Individuals with prior lumbar fusion
People with autoimmune or inflammatory conditions
Athletes or laborers with repetitive pelvic stress
Those with leg length differences or scoliosis
Low Back Frequently Asked Questions
01. What is a facet ablation (RFA), and how is it different from diagnostic blocks?
Answer: Blocks test the pain source; ablation stops the nerve signal.
A medial branch block temporarily numbs a spinal joint to confirm the pain generator. If it works, radiofrequency ablation (RFA) uses heat to deactivate that small nerve for 6–12 months. The joint stays stable, and pain often lessens dramatically.
Lumbar | Interventional Spine | RFA
02. How long does a radiofrequency ablation (RFA) last, and can it be repeated?
Answer: Relief often lasts 6–12 months and the procedure can be repeated safely.
After an RFA, the tiny sensory nerves that send pain signals grow back slowly. Many patients enjoy meaningful relief for 6 months to a year. If the pain returns, a repeat ablation can usually be performed using the same approach. Regular stretching and strengthening help extend the benefit. Lumbar | Cervical | Interventional Spine | RFA
03. Why does my low back hurt after sitting or long drives?
Answer: It’s usually from facet-joint stress or weak postural muscles.
Sitting flexes the lumbar spine and compresses facet joints and discs, especially if the core is de-conditioned. Over time, this posture leads to inflammation and stiffness. Supportive cushions, regular breaks, and targeted therapy for core and glute muscles often relieve symptoms.
Lumbar | Ergonomics | Rehab
04. What is a diagnostic discogram, and why is it rarely done now?
Answer: It injects dye into spinal discs to find the pain source but carries risks.
Discography involves pressurizing discs with contrast dye while monitoring pain response. It was once common before spine surgery but is now less used because it can worsen disc damage and cause infection. Modern MRI and targeted nerve blocks provide safer diagnostic insight.
05. Why do some people have chronic back pain even after “successful” fusion surgery?
Answer: Adjacent levels often wear out faster.
Spinal fusion stabilizes one level but transfers stress to the discs and joints above and below, leading to adjacent segment disease. Scar tissue, muscle atrophy, and nerve irritation can also persist. Nonsurgical options like PRP or radiofrequency treatment can help preserve the surrounding spine.
Lumbar | Post-Surgery | Interventional Spine
06. What are “adjacent segment disease” and “hardware failure” after spine surgery?
Answer: They mean nearby levels or implants break down over time.
After fusion, joints next to the fused area compensate by moving more, sometimes developing arthritis or stress fractures. Hardware fatigue or loosening can also occur years later. Regular imaging helps detect changes early; pain-management injections or strengthening programs can often delay revision surgery.
Lumbar | Cervical | Post-Surgery | Spine Degeneration
07. How do you tell if leg pain is from the back or from a knee or hip problem?
Answer: Back-related pain travels below the knee; joint pain usually stays local.
Nerve compression in the spine typically causes sharp, shooting pain that radiates past the knee or into the foot. Hip or knee arthritis usually creates aching localized pain or stiffness without tingling. Imaging and physical-exam maneuvers help determine whether the source is spinal, joint, or both.
Diagnostics | Lumbar | Hip | Knee
08. What is an epidural steroid injection and what does it do?
Answer: It delivers anti-inflammatory medicine around pinched nerves.
Guided by X-ray, a thin needle places medication into the epidural space of the spine. The steroid reduces swelling around irritated nerves from a herniated disc or arthritis. Relief may last weeks to months and can allow better participation in physical therapy.
Interventional Spine | Epidural | Lumbar | Cervical
09. What are red-flag symptoms that spine pain is not just mechanical?
Answer: Fever, unexplained weight loss, numbness, or bladder issues.
Warning signs include constant pain at rest, night sweats, progressive weakness, loss of control of urine or stool, or recent infection. These could signal infection, tumor, or severe nerve compression and need emergency evaluation.
Safety | Lumbar | Cervical | Emergency
10. How long should I wait before considering spine surgery?
Answer: Only after conservative care has clearly failed and red flags are excluded.
Most mechanical back or neck pain improves with guided injections, therapy, or biologic repair within 3–6 months. Surgery is reserved for progressive weakness, structural instability, or nerve compression causing loss of function. A second opinion is always appropriate before proceeding.
Lumbar | Cervical | Surgery Decision
11. What is a “facet joint,” and why can it cause back or neck pain?
Answer: It’s a small stabilizing joint behind each vertebra that can become arthritic.
Facet joints allow bending and twisting. With aging or injury, they may develop arthritis and inflammation that causes sharp localized pain, often worse when leaning backward or standing long periods. Facet injections or RFA can calm these joints for months at a time.
Lumbar | Cervical | Anatomy | Interventional Spine
12. When should I seek emergency care after a neck or back injury?
Answer: Sudden weakness, numbness, fever, or bladder/bowel changes.
Go to the ER immediately for severe pain with loss of strength, incontinence, high fever, or trauma with head injury. These could indicate nerve or spinal-cord compression, infection, or fracture. Early treatment prevents permanent damage.
Cervical | Lumbar | Emergency | Safety
13. What is a “nerve root block,” and how is it different from an epidural?
Answer: A nerve-root block targets one specific nerve, while an epidural bathes several.
A selective nerve-root block (SNRB) uses live X-ray to deliver medication directly around one irritated spinal nerve. It helps confirm which nerve causes the pain and can calm inflammation at that precise level. Epidural injections are broader, covering multiple nerves at once.
14. How can I tell if my hip pain is coming from the joint or my back?
Answer: Hip arthritis hurts in the groin; back problems radiate to the leg.
Hip joint disease often causes deep aching in the groin or front thigh, worse with walking or stairs. Lumbar nerve compression tends to cause burning or tingling down the leg. Diagnostic injections into the hip or spine can confirm the true source.
Hip | Lumbar | Diagnostics | Joint Pain
15. Can regenerative medicine help spine patients who already have hardware or fusions?
Answer: Yes, but injections are placed around not into the fused levels.
PRP and bone-marrow concentrate can reduce inflammation in joints and ligaments next to a fusion where new pain develops. These procedures don’t interact with the hardware itself. Most patients benefit from improved flexibility and less reliance on pain medication.
Spine | Post-Surgery | Orthobiologics | Interventional Spine
When to See a Specialist
If you’re experiencing persistent buttock or hip pain, especially one-sided or activity-related, an SI-focused evaluation can determine if sacroiliitis is the cause.
Early identification prevents chronic pain and restores movement.
Minimally invasive spine & joint care.
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