Q&A Topic: Is Your SI Joint Causing Your Back Pain?

Marshal D. Peris, MD, FAAOS

Q. What is the SI joint?

A. The full name is the sacroiliac (sa-krō-ˈi-lē-ˌak) joint, and there are two of them, one on either side of your tailbone. They connect the triangular bone at the base of your spine, called the sacrum, with the iliac bone of your pelvis. The SI joints are the “keystone” of the body, or the center of gravity. Their job is to support and transmit the weight of your upper body to your legs and pelvis.

Q. How does the SI joint cause pain?

A. “SI joint dysfunction” occurs when the ligaments and/or cartilage of either joint are injured or worn away. This can cause pain in your butt as well as in your lower back, groin, thigh and side. Most people with SI joint dysfunction experience severe pain when they get up from a seated position, then feel better when they walk.

Q. What causes SI joint dysfunction?

A. Osteoarthritis, rheumatological and auto-immune diseases, traumatic injuries and pregnancy can cause SI joint dysfunction. And some people get it after they’ve had surgeries such as hip replacement or spinal fusion.

Q. How does the doctor diagnose SI joint dysfunction?

A. It’s important to see your primary care physician if you’re experiencing pain. You’ll likely be referred to a spine specialist or orthopedist who will carry out further testing. The doctor first rules out the spine by doing imaging like X-rays and MRIs. There are also physical exam maneuvers that can pinpoint trouble in the SI joint.

Q. How is SI joint dysfunction treated?

A. The first lines of treatment are physical therapy, weight loss, trunk-strengthening exercises like yoga or Pilates, and anti-inflammatory medicines. If these don’t help, doctors inject a steroid and local anesthetic into the joint, a procedure called “SI joint injection.” For some patients, a single injection solves the problem. For others, the treatment works initially but the pain comes back in several months to a year, so the doctors do additional injections, but no more than three total.  

Q. What if these treatments don’t work?

A. If there is still no improvement after physical therapy, exercises and SI joint injection, doctors perform a minimally invasive surgery called “SI joint fusion.” Titanium implants are inserted across the sacroiliac joint through a 3-cm incision to lock the joint in place so it can’t move anymore. The surgery takes about an hour and is done under general anesthesia at Northern Westchester Hospital. For the first three weeks after surgery, patients walk with crutches or a walker. After six weeks, they resume normal activities.

Learn More About Dr. Peris
Co-Director, Spine Surgery
Orthopedic and Spine Institute
Northern Westchester Hospital

Northern Westchester Hospital is a proud member of Northwell Health.


Read Past Topics from Dr. Peris: 
Scoliosis and Lateral Spine Fusion
Cervical Spine Disc Replacement 
Cervical Stenosis 
Preventing Chronic Back Pain – Starting Today

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