If you have ever had a dull ache deep in your lower back or buttock, you might have blamed a strained muscle or a disc problem. But research shows that up to 30 percent of all lower back pain actually comes from a joint most people have never heard of: the sacroiliac joint, also called the SI joint.
Understanding what this joint does, why it hurts, and how to treat it can make a real difference for people who have been dealing with one-sided back or hip pain that refuses to get better.
Key Stat: Up to 30% of chronic lower back pain is caused by the sacroiliac joint, according to a 2025 systematic review of 2,666 patients in the European Journal of Orthopaedic Surgery and Traumatology.
What Is the Sacroiliac Joint?
You have two sacroiliac joints, one on each side of your lower spine. They sit where the triangular sacrum bone at the base of your spine meets the large hip bones on either side. You can roughly feel them at the two small dimples just above your buttocks.
These joints barely move. Their job is to absorb shock and transfer the weight of your upper body down into your legs when you stand, walk, or bend. Strong ligaments hold them in place, but all that daily force adds up over time.
What Does SI Joint Pain Feel Like?
SI joint pain usually feels like a dull ache or sharp pain in the lower back, hip, or buttock, most often on one side. About 28 percent of people with SI joint problems also feel pain traveling down the back of the leg, which can look almost exactly like sciatica.
The pain is often worse after:
- Sitting or standing for long periods
- Getting up from a chair
- Climbing stairs or walking uphill
- Lying on the affected side at night
A 2024 review in Skeletal Radiology noted that SI joint dysfunction is frequently missed because the symptoms overlap so closely with disc and nerve conditions.
What Causes SI Joint Pain?
Several things can irritate or destabilize the SI joint:
- Injury or trauma: A fall onto the hip, a car accident, or a sudden awkward twist can strain the ligaments holding the joint together.
- Repetitive stress: Heavy lifting, prolonged standing, or always loading one side of your body puts steady pressure on the joint.
- Pregnancy: Hormonal shifts loosen the pelvic ligaments to prepare for childbirth. That looseness can leave the SI joint unstable long after delivery.
- Arthritis: Degenerative wear or inflammatory types like ankylosing spondylitis can break down the joint itself.
- Leg length differences: Even a small discrepancy changes how weight passes through the pelvis, stressing one SI joint more than the other.
How Is SI Joint Pain Treated?
Most SI joint pain responds well to conservative care. The 2025 systematic review mentioned above analyzed 2,666 patients and found that non-surgical treatment forms the foundation of SI joint management. That includes chiropractic care, physical therapy, anti-inflammatory medications, and activity changes.
A 2023 randomized controlled trial of 120 patients found that combining motor control exercises with balance training produced better outcomes for SI joint pain than either approach used on its own. The combination significantly reduced pain scores and improved daily function.
For cases that do not respond to conservative care, guided injections or radiofrequency procedures are options. Surgery is rarely necessary.
Simple Exercises You Can Do Right Now
These three moves target the muscles that stabilize the SI joint. Go slowly and stop if any movement causes sharp or radiating pain.
- Bird-dog: Start on hands and knees. Extend your right arm and left leg at the same time. Hold five seconds. Switch sides. Aim for 8 to 10 reps per side.
- Clamshell: Lie on your side with knees bent and feet together. Lift your top knee toward the ceiling. Hold two seconds. Do 15 reps per side.
- Supine pelvic tilt: Lie on your back with knees bent. Press your lower back gently into the floor. Hold five seconds, then release. Repeat 10 times.
If your pain is not improving, a lower back pain specialist can assess whether the SI joint is the source and build a treatment plan around your specific situation.
How to Prevent SI Joint Pain Going Forward
- Take movement breaks. Standing and walking for a few minutes every hour keeps the joint from stiffening and shifts the load.
- Avoid leaning on one leg. Habitually shifting your weight to one hip puts uneven pressure on that side of the pelvis.
- Strengthen your glutes and core. These muscles share the job of supporting the SI joint every time you move.
- Wear supportive footwear. Poor shoes change your gait and create stress throughout the entire pelvis.
The Bottom Line
The SI joint is responsible for a much larger share of lower back pain than most people realize. Up to 30 percent of chronic low back pain traces back to this area, yet many people spend years without the right diagnosis.
Most cases get better with targeted exercise, manual therapy, and simple habit changes. If you have had one-sided lower back, hip, or buttock pain that is not responding to standard treatment, it is worth asking your provider whether your sacroiliac joint might be playing a role.
Sources & Further Reading
- Migliorini F, et al. Management of sacroiliac joint pain: current concepts. European Journal of Orthopaedic Surgery and Traumatology. 2025. PMC12095441
- Waldman SD. Sacroiliac joint dysfunction: anatomy, pathophysiology, differential diagnosis, and treatment approaches. Skeletal Radiology. 2024. PubMed 39556269
- Szadek KM, et al. Sacroiliac joint pain. Pain Practice. 2024. PubMed 38155419
- Alqhtani RS, et al. Synergistic Benefits of Motor Control Exercises and Balance Training in Sacroiliac Joint Dysfunction: A Randomized Controlled Trial. Life (MDPI). 2023. PMC10745022
