The sacroiliac (SI) joints are where the base of your spine (sacrum) meets your pelvis (ilium). Sacroiliitis is inflammation of one or both of these joints. It's a common but underdiagnosed cause of low back and buttock pain, often mistaken for disc issues or sciatica.
Types of sacroiliitis
Mechanical — from asymmetric loading, prolonged sitting, pregnancy, or a specific injury. This is what we see most often in the clinic.
Inflammatory — associated with spondyloarthropathies like ankylosing spondylitis, psoriatic arthritis, or inflammatory bowel disease. This kind needs medical management alongside our care.
The classic pattern
- Pain localized to one side of the lower back, at the dimple just below the belt line
- Pain in the buttock, often described as "deep"
- Sometimes referring down the back of the thigh but rarely below the knee
- Worse with prolonged sitting, standing on one leg, climbing stairs, getting out of a car
- Better with walking or changing position
How to tell it from disc pain
Disc pain usually refers below the knee and includes neurological symptoms (numbness, weakness). SI joint pain typically stops at the knee and doesn't have significant nerve findings. Provocation tests during a physical exam help isolate the SI joint as the pain source.
Our treatment approach
Joint mobilization / manipulation of the SI joint — often produces significant immediate relief in mechanical cases.
Soft tissue work on the piriformis, glute medius, and QL — muscles that guard around a cranky SI joint.
Core and glute strengthening — the SI joint is stabilized dynamically by the surrounding muscles. Weakness lets it become chronically irritable.
Movement pattern correction — walking, standing, sitting habits often need reset.
Acupuncture and dry needling for pain modulation, especially in acute flares.
When we refer
If we suspect inflammatory SI disease (younger patient, morning stiffness > 30 minutes, systemic symptoms), we coordinate with a rheumatologist. Medical management combined with conservative care gets these patients the best outcomes.
If your low back or buttock pain has been dismissed as "just muscular" and hasn't resolved, come in for a proper SI assessment.