Understanding Pain in the SI Joint
The sacroiliac (SI) joints connect the base of the spine (sacrum) to the pelvis on each side. They support your body weight and absorb shock with every step. When an SI joint becomes irritated or moves abnormally, it can cause significant low back and buttock pain that is often mistaken for a lumbar spine problem.
Causes
SI joint pain can develop from several causes:
Ligament laxity from pregnancy, which can loosen the joint.
A fall or direct trauma to the buttock or pelvis.
Degenerative changes or arthritis within the joint over time.
Repetitive asymmetric loading, like always favoring one leg.
Stress on the SI joint after a prior lumbar spinal fusion.
Inflammatory sacroiliitis (as seen in conditions like ankylosing spondylitis) is a different underlying process that your doctor will screen for.
Leg length discrepancy.
Symptoms
Typical symptoms include:
Pain in the low back and buttock, just below the belt line, usually on one side.
Pain that may radiate into the back of the thigh, but typically not below the knee.
Pain that worsens with prolonged sitting or standing.
Pain with transitional movements: going from sitting to standing, or rolling over in bed.
Discomfort climbing stairs or stepping up.
Seek prompt medical care if: You develop new loss of bladder or bowel control, numbness in the groin or inner thighs, or rapidly worsening leg weakness. Also seek prompt care for back pain with fever, unexplained weight loss, a history of cancer, or after significant trauma.
Imaging Studies to Consider
Imaging and diagnostic testing help confirm the SI joint as the pain source:
X-ray of the pelvis/SI joints evaluates joint alignment and degenerative changes.
MRI of the sacroiliac joints is particularly helpful if inflammatory sacroiliitis is suspected, showing bone marrow changes.
CT scan is used for detailed bony evaluation, especially before certain procedures.
Diagnostic SI joint injection: a targeted injection of numbing medication is often the most reliable way to confirm the SI joint is the true source of pain.
Physical Therapy, Home Exercise & Other Conservative Techniques
Stabilization exercises and a supportive SI belt are typically tried first for sacroiliac joint pain:
Physical Therapy
SI joint stabilization exercises.
Manual therapy for the pelvis and low back.
Gait and movement pattern retraining.
Home Exercise Program
Core and pelvic stabilization exercises.
Glute strengthening exercises.
Other Studied Techniques
An SI belt to provide external support and stability.
Activity modification, avoiding asymmetric loading (standing on one leg, high step-ups).
Heat for muscle tension around the joint.
Interventional Treatment Options
Interventional treatments can both confirm and treat SI joint pain:
Image-guided SI joint injection: A corticosteroid and anesthetic injected directly into the joint under x-ray or ultrasound guidance is both diagnostic and therapeutic.
Lateral branch radiofrequency ablation: Uses heat to disable the small sensory nerves (lateral branches) that carry pain signals from the SI joint, offering longer-lasting relief than injection alone.
Platelet-rich plasma (PRP) injection: In patients who've had a positive diagnostic block confirming the SI joint as the pain source, intra-articular PRP appears to offer more durable relief than a corticosteroid injection into the same joint. Typically given as a single injection or short series.
Acupuncture: A technique that may help with associated low back and buttock pain as part of a broader treatment plan.
Minimally invasive SI joint fusion: For patients with confirmed SI joint pain that doesn't respond to injections and radiofrequency ablation, surgical referral for joint stabilization may be appropriate.
Neuromodulation: Spinal Cord & Peripheral Nerve Stimulation
For chronic SI joint pain that persists despite the above treatments, or when it's part of broader chronic low back pain, neuromodulation is an option:
Peripheral nerve stimulation (PNS) of the lateral branches: A small electrode placed near the nerves supplying the SI joint to provide ongoing pain relief without opioids.
Spinal cord stimulation (SCS): May be considered for widespread chronic low back pain that includes an SI joint component.
How Strong Is the Evidence?
A summary of the evidence supporting key treatments for SI joint pain:
How to read this: Strong means consistent results from multiple high-quality studies. Moderate means generally favorable results with some limitations. Mixed or early means results so far are inconsistent or still emerging. Limited means few or lower-quality studies; these options can still be considered in select cases following a discussion with your healthcare provider.
Diagnostic/therapeutic SI joint injection: Moderate evidence.
Lateral branch radiofrequency ablation: Moderate evidence.
Minimally invasive SI joint fusion: Moderate evidence.
Acupuncture (adjunctive): Limited evidence.
Platelet-rich plasma (PRP): Strong evidence.
Evidence reviewed November 2026. These ratings summarize published research and major medical society guidelines available at that time. Research continues to evolve, and we will go over the most current evidence for your situation at your visit.
Pain Psychology Techniques
Pain psychology techniques help manage the impact of chronic SI joint pain on daily activity:
Cognitive behavioral therapy (CBT) for pain addresses thoughts and behaviors that can worsen chronic pain.
Graded activity pacing helps you stay active without provoking flare-ups from prolonged sitting or standing.
Relaxation training and diaphragmatic breathing.
Mindfulness-based stress reduction.
Non-Opioid Medication Options
Non-opioid medications can help manage SI joint pain:
Anti-inflammatory and analgesic options
NSAIDs like ibuprofen, naproxen, or meloxicam can reduce inflammation in the joint.
Acetaminophen for additional pain relief.
For associated muscle spasm or chronic pain
Muscle relaxants (short-term), like cyclobenzaprine or tizanidine, for associated muscle tightness.
Duloxetine is an SNRI antidepressant also approved for chronic musculoskeletal pain.
Related Procedures
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Talk With Us About Your Options
Call 650-507-4113 or send us a message to schedule a consultation at our Daly City, Los Altos, or Stockton office. We will review what may be causing your pain and walk through the risks, benefits, and alternatives of each option with you.
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This information is provided for general patient education and does not replace individualized medical advice. Please discuss your specific symptoms, diagnosis, and treatment options with your pain management physician.
