Sacroiliac Joint Pain: The Overlooked Cause of Low Back Pain
If you have chronic low back pain, hip pain, or buttock pain — and your spine MRI looks relatively normal — there's a good chance your sacroiliac (SI) joint is contributing to your symptoms. SI joint dysfunction is estimated to cause 15–30% of chronic low back pain cases, yet it remains consistently underdiagnosed.
What Is the Sacroiliac Joint?
The SI joint connects the sacrum (the triangular bone at the base of the spine) to the ilium (the large pelvic bone on each side). It's a large, strong joint that bears the mechanical load of the upper body and transmits it to the legs. Despite its stability, the SI joint can become inflamed, arthritic, or dysfunctional — causing significant pain.
Recognizing SI Joint Pain
SI joint pain typically presents as:
- One-sided pain centered at the dimple of the lower back and buttock
- Pain that may radiate to the groin, hip, or back of the thigh — but usually not below the knee
- Worsening with prolonged sitting, especially on the affected side
- Difficulty with activities that stress the joint: climbing stairs, rolling in bed, walking uphill
- Point tenderness directly over the posterior superior iliac spine (PSIS)
Why It's Often Missed
SI joint dysfunction doesn't show up reliably on MRI or X-ray. Imaging can show arthritis changes, but the absence of imaging findings doesn't rule out SI joint pain. Diagnosis requires clinical assessment (provocation tests on physical examination) and diagnostic SI joint injections — injections of local anesthetic into the joint that temporarily relieve symptoms and confirm the diagnosis.
Treatment Options
SI Joint Injections: Corticosteroid injections into the SI joint reduce inflammation and provide diagnostic and therapeutic relief lasting weeks to months.
Physical Therapy: SI joint stabilization exercises targeting the core, hip abductors, and pelvic floor musculature can significantly reduce symptoms and prevent recurrence.
Radiofrequency Ablation of Lateral Branch Nerves: Ablation of the lateral branch nerves that innervate the SI joint — similar to medial branch ablation for facet pain — provides longer-lasting relief than repeated injections.
Minimally Invasive SI Joint Fusion: For patients who respond to injections but have insufficient duration of relief, minimally invasive SI joint fusion (using titanium implants placed through a small lateral incision) provides long-lasting stabilization. Published randomized trials show significantly superior outcomes compared to continued non-surgical management.
Special Consideration: Post-Partum SI Joint Pain
SI joint pain is particularly common in women after pregnancy and childbirth — the relaxin hormone released during pregnancy loosens the SI joint, and trauma during delivery can destabilize it. This is a common and treatable cause of persistent low back pain after having a baby.
If you have low back, buttock, or hip pain that hasn't been adequately explained, call 516-492-3100 to discuss whether the SI joint might be a contributing factor.