Sacroiliac Joint Injection: Diagnosis, Treatment & Recovery
Sacroiliac Joint Injection, often called an SI joint injection, is an image-guided procedure used to diagnose and treat pain coming from the sacroiliac joint. The sacroiliac joint sits where the sacrum, the triangular bone at the base of the spine, meets the pelvis.
SI joint pain can mimic low back pain, hip pain, buttock pain, and sometimes leg pain. Patients may be told they have sciatica, lumbar arthritis, disc disease, or hip bursitis before the SI joint is recognized as a possible pain generator.
An SI joint injection can be used diagnostically, therapeutically, or both. The local anesthetic helps confirm whether the joint is responsible for pain. The steroid may reduce inflammation and provide longer relief in selected patients.
What Is a Sacroiliac Joint Injection?
A sacroiliac joint injection places medication into the SI joint under imaging guidance. The medication usually includes a local anesthetic and corticosteroid.
The local anesthetic may provide temporary numbness. If the patient’s usual pain improves during the expected anesthetic window, this supports the diagnosis of SI joint-mediated pain.
The corticosteroid is intended to reduce inflammation inside the joint and around the joint capsule. Relief may develop over several days.
Where Is the Sacroiliac Joint?
The sacroiliac joints are located on the left and right sides of the pelvis, where the sacrum joins the ilium. These joints transfer force between the upper body and legs.
The SI joint has limited motion, but it carries major mechanical load. When irritated, inflamed, unstable, or arthritic, it can create pain that feels deceptively similar to lumbar spine pain.
Common Symptoms of SI Joint Pain
SI joint pain often causes pain below the beltline, near the dimples of the low back, buttock, or back of the hip.
Symptoms may include:
- Low back pain below L5
- Buttock pain
- Pain near the posterior pelvis
- Pain with sitting, standing, or walking
- Pain when rising from a chair
- Pain climbing stairs
- Pain rolling over in bed
- Pain after pregnancy or pelvic trauma
- Pain after lumbar fusion or altered spinal mechanics
SI joint pain can sometimes refer into the groin, thigh, or leg, but it usually does not follow a clean nerve-root pattern like true radiculopathy.
SI Joint Pain vs Sciatica vs Facet Pain
SI joint pain is often mistaken for other conditions. The table below helps separate common patterns.
| Condition | Typical Pain Pattern | Clues |
|---|---|---|
| SI Joint Pain | Low back, buttock, posterior pelvis, sometimes groin or thigh | Worse with transitional movements, stairs, standing on one leg, rolling in bed |
| Sciatica / Radiculopathy | Shooting or burning pain down the leg, often below the knee | Numbness, tingling, weakness, nerve-root pattern |
| Facet Joint Pain | Low back stiffness, buttock or upper thigh referral | Worse with extension, standing, twisting |
| Hip Joint Pain | Groin, front of thigh, sometimes buttock | Worse with hip rotation, getting in/out of car, putting on shoes |
If your pain travels down the leg with numbness or tingling, review our sciatica page. If pain is more spine-extension related, review facet joint syndrome.
How SI Joint Pain Is Diagnosed
SI joint diagnosis usually requires several layers of information. No single physical exam finding or MRI report proves the SI joint is the pain source.
The diagnostic process may include:
- Detailed history
- Location of pain
- Provocative SI joint maneuvers
- Evaluation of lumbar spine, hip, and nerve-root causes
- Imaging when appropriate
- Image-guided diagnostic SI joint injection
Common provocative tests include FABER, thigh thrust, compression, distraction, Gaenslen’s test, and sacral thrust. A cluster of positive provocative tests increases suspicion, but diagnostic injection is often used when confirmation is needed.
Why Image-Guided Injection Matters
The SI joint is deep, narrow, and irregular. Blind injections may miss the joint.
Fluoroscopy or CT guidance helps confirm accurate needle placement. Contrast dye is commonly used to verify that the medication enters the joint or reaches the intended periarticular region.
This is important because the diagnostic value of the injection depends on accurate placement.
Diagnostic vs Therapeutic SI Joint Injection
Diagnostic SI Joint Injection
A diagnostic injection uses local anesthetic to test whether numbing the SI joint significantly reduces the patient’s usual pain.
Many protocols consider meaningful pain relief during the expected anesthetic window supportive of SI joint-mediated pain. Some references use thresholds such as 50%, 70%, or 75% relief depending on payer policy, study design, and clinical context.
Therapeutic SI Joint Injection
A therapeutic injection adds corticosteroid to reduce inflammation. Relief may last weeks to months in selected patients, although results vary.
The injection is best used as part of a broader plan that may include physical therapy, pelvic stabilization, gait correction, weight management, and treatment of coexisting lumbar or hip disorders.
Who May Benefit From Sacroiliac Joint Injection?
A patient may be a candidate if they have:
- Low back or buttock pain suspected to arise from the SI joint
- Pain below the L5 level near the posterior pelvis
- Positive SI joint provocative tests
- Pain after pregnancy, trauma, fall, or lumbar fusion
- Symptoms not fully explained by lumbar MRI or hip imaging
- Persistent pain despite conservative care
- Need for diagnostic confirmation before advanced SI treatment
How the Procedure Is Performed
A sacroiliac joint injection is typically performed in an outpatient setting.
- The patient lies face down on the procedure table.
- The skin over the low back and pelvis is cleaned using sterile technique.
- Local anesthetic is used to numb the skin.
- A thin needle is guided toward the SI joint using fluoroscopy or CT guidance.
- Contrast dye is injected to confirm placement.
- Local anesthetic and, when appropriate, corticosteroid are injected.
- The patient is monitored briefly before discharge.
The injection itself is usually brief, but the full visit includes preparation, positioning, monitoring, and discharge instructions.
What to Expect After the Injection
If local anesthetic is used, some patients feel relief within minutes. This early response is diagnostically important.
Steroid benefit may take several days to develop. Some patients have temporary soreness or a short pain flare after the procedure.
Aftercare may include:
- Light activity the day of the procedure
- Avoiding strenuous activity for 24 to 48 hours unless instructed otherwise
- Tracking pain relief during the first several hours
- Noting whether sitting, standing, stairs, or walking improve
- Restarting therapy or home exercise when appropriate
What the Research and Guidelines Say
The 2024 American Society of Pain and Neuroscience best-practice guideline recommends image-guided intra-articular corticosteroid injections for persistent SI joint pain after conservative care has failed for several weeks.
Research also emphasizes that physical exam findings alone are imperfect, and image-guided diagnostic injections may help confirm the SI joint as the pain generator.
Therapeutic durability varies. Some patients experience meaningful relief, while others have short-term or limited benefit. This is why the injection is often part of a stepwise care pathway rather than a one-stop cure.
Where PRP, BMAC, and Biologic Treatments Fit
Some patients prefer to avoid repeated corticosteroid injections or are interested in regenerative options.
Biologic options sometimes discussed for SI joint-related pain include:
- PRP: Platelet-rich plasma prepared from the patient’s own blood
- BMAC: Bone marrow aspirate concentrate containing platelets, signaling proteins, and marrow-derived cells
- Cellular or matrix-based products: Sometimes marketed as stem cell matrix or tissue allograft products
These treatments are not the same as a standard diagnostic SI joint injection. Evidence for biologic SI joint treatment is still evolving, and insurance coverage is often limited or absent.
Patients should understand the goals, cost, regulatory status, and evidence limits before choosing PRP, BMAC, or cellular/matrix-based treatments.
SI Joint Radiofrequency Ablation
SI joint radiofrequency ablation targets the sensory nerve supply around the posterior sacroiliac joint, often including lateral branches from the sacral region.
This treatment may be considered when SI joint pain is confirmed and conservative care or injections do not provide durable relief.
Authorization for SI joint RFA can be challenging because payer policies vary. Some insurance plans treat SI RFA differently from lumbar facet RFA, and coverage may depend on documentation, diagnostic block response, and policy language. Given the safety profile and success rates of sacroiliac joint stabilization/fusion procedures, SI Joint radiofrequency ablation procedure is slowly getting outdated.
When SI Joint Fusion Is Considered
SI joint fusion is generally reserved for carefully selected patients with confirmed SI joint pain who do not respond adequately to conservative care, injections, rehabilitation, and other less invasive options.
Fusion is not a first-line treatment. It is considered only after diagnosis is carefully confirmed.
Posterior SI Joint Fusion
Posterior SI joint fusion systems, including approaches such as LinQ-type posterior fusion, are designed to stabilize the SI joint through a posterior approach. The evidence base is growing, including recent studies suggesting sustained pain and function improvement in selected patients.
Lateral SI Joint Fusion
Lateral SI joint fusion systems, including implant-based approaches such as SACRIX-type lateral fusion, stabilize the joint by crossing from the ilium into the sacrum. This is a more traditional fusion corridor compared with purely posterior approaches.
The choice between posterior and lateral approaches depends on anatomy, diagnosis, surgeon experience, implant system, payer policy, and patient-specific risk factors.
When Sacroiliac Joint Injection May Not Be the Right Procedure
SI joint injection is less likely to help if pain is primarily caused by:
- Disc herniation with nerve compression
- Sciatica or radiculopathy
- Facet joint syndrome
- Vertebrogenic pain
- Hip arthritis
- Peripheral neuropathy
- Purely muscular pain
This is why diagnostic precision matters. The SI joint is a common suspect, but it should not be blamed without evidence.
SI Joint Treatment Pathway: Choose What Fits Best
Dr. Amit Sharma and the SpinePain Solutions team evaluate SI joint dysfunction, lumbar spine pain, sciatica, facet pain, and related conditions across Long Island.
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Frequently Asked Questions About Sacroiliac Joint Injection
What is a sacroiliac joint injection?
A sacroiliac joint injection is an image-guided injection of local anesthetic and sometimes corticosteroid into the SI joint to help diagnose or treat SI joint-related pain.
Is SI joint injection diagnostic or therapeutic?
It can be both. Local anesthetic helps confirm whether the SI joint is the pain source. Steroid may reduce inflammation and provide longer relief.
Where is SI joint pain usually felt?
SI joint pain is often felt below the beltline near the back of the pelvis, buttock, hip region, or groin. It may sometimes refer into the thigh.
How is SI joint pain different from sciatica?
Sciatica usually causes burning, shooting, or electric pain traveling down the leg, often below the knee, sometimes with numbness or tingling. SI joint pain is more often buttock or pelvic pain worsened by transitions, stairs, or standing.
How soon will I feel relief after SI joint injection?
Local anesthetic may help within minutes or hours. Steroid benefit may take several days. Diagnostic relief during the anesthetic window is especially important.
How long does relief last?
Relief varies. Some patients get weeks to months of improvement, while others get shorter relief. The result depends on diagnosis, inflammation, mechanics, and rehabilitation.
Is SI joint injection safe?
SI joint injections are commonly performed and generally well tolerated when done with image guidance and sterile technique. Risks include soreness, bleeding, infection, allergic reaction, and temporary pain flare.
Can PRP or BMAC be used for SI joint pain?
PRP and BMAC may be considered in selected patients, but they are not the same as standard SI joint steroid injections. Evidence is evolving and insurance coverage is often limited.
What if SI joint injection does not last?
If diagnostic relief is strong but temporary, options may include rehabilitation, repeat injection in selected cases, SI joint RFA if covered, biologic treatment discussion, or fusion evaluation in carefully selected patients.
When is SI joint fusion considered?
SI joint fusion is generally considered only after SI joint pain is carefully confirmed and conservative care, injections, and less invasive treatments have failed to provide adequate relief.
References
- Sayed D, et al. American Society of Pain and Neuroscience Best Practice Guideline for the Treatment of Sacroiliac Disorders. 2024.
- NCBI Bookshelf: Sacroiliac Joint Injection. Updated 2023.
- CMS Local Coverage Determination: Sacroiliac Joint Injections and Procedures.
- Liu Y, et al. Comparative efficacy of clinical interventions for sacroiliac joint pain: systematic review and network meta-analysis. Neurospine. 2023.
- Lee DW, et al. Review of current evidence for minimally invasive posterior sacroiliac joint fusion. 2021.
- Bovinet C, et al. Minimally invasive posterior SI joint fusion with a cortical allograft implant. 2025.
- Martin CT, et al. Minimally invasive sacroiliac joint fusion: current evidence. 2020.
- Cleveland Clinic: Sacroiliac Joint Fusion. Updated 2025.
