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SI (sacroiliac) joint fusion is a surgical procedure to permanently join the sacrum and ilium bones at your sacroiliac joint. Your provider might suggest it if you have severe low back pain that nonsurgical treatments can’t manage. Sacroiliac joint fusion has a good success rate and a low risk of long-term complications.
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SI joint fusion is a surgery that permanently connects the bones in one of your sacroiliac (SI) joints. These joints link your spine to your pelvis. This is where the triangle-shaped bone at the base of your spine (sacrum) meets the upper part of your pelvis (ilium).
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Your doctor may recommend this procedure if you have ongoing lower back pain, or sacroiliitis, that didn’t get better with nonsurgical treatments.
It’s a type of joint fusion surgery (called arthrodesis). There are two forms:
Healthcare providers shorten the term “sacroiliac joint” to “SI joint,” so you might see this procedure called:
These are all different names for the same procedure.
You’ll meet with your healthcare provider and surgeon before surgery. They’ll ask about your symptoms and how much they affect your daily routine and quality of life. They’ll review which nonsurgical treatments you’ve tried and ask how well they’ve worked.
It can be scary to consider surgery, but don’t shortchange your experiences. If lower back pain, stiffness or other symptoms make day-to-day activities hard, be honest with your providers.
Your surgeon will tell you when you should fast (stop eating and drinking). Most people need to fast for 12 hours before the procedure.
The day of your surgery, an anesthesiologist will give you general anesthesia. This will put you to sleep. You won’t feel any pain.
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During the SI joint fusion, your surgeon will:
As you heal, the bones in your sacroiliac joint will grow together and become one. This makes the joint stronger, more stable and less painful.
SI joint fusion usually takes around an hour. Your surgeon will tell you what to expect.
Sacroiliac joint fusion often leads to a better quality of life. Many people have much less back pain after they recover. It’s a safe and effective option when other treatments haven’t worked.
People usually say the surgery reduces their pain by at least half, even years later. You might still have occasional pain. But you should be able to return to all your usual physical activities, including exercising and playing sports.
Experts estimate that more than 4 out of 5 people who need SI joint fusion have a successful outcome. That means they have noticeable, lasting pain relief. Talk to your surgeon about what you can expect.
Immediate side effects are rare after sacroiliac joint fusion, but can include:
After surgery, it’s important to watch for symptoms like pain that doesn’t get better or comes back, or swelling and warmth near the joint. These could be signs of what doctors call a “failed SI joint fusion.” While rare, this means the joint isn’t healing as expected and might need another surgery to fix the problem.
Some people have lasting limits in SI joint movement after surgery. As the procedure fuses two bones into one, the joint may not move as freely or smoothly. Rarely, you may develop new or worsening pain in other areas of your back.
You’ll probably have a small scar at your surgery site. The cuts (incisions) surgeons make are usually only a few inches long, so any scarring should be small, too. Ask your surgeon for tips to help your body heal and minimize scarring.
SI joint fusion is usually an outpatient procedure, which means you can go home the same day. Your surgeon will probably tell you to start moving and walking right after the procedure. You might need a walker or a cane to avoid putting too much weight or pressure on your surgery site.
It can take a few months to recover fully after sacroiliac joint fusion.
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Right after surgery, you should:
You might need physical therapy to help you regain your strength after SI joint fusion.
Most people can restart all of their usual physical activities three or four months after surgery. Your surgeon will give you a customized recovery timeline. They’ll tell you which activities, movements or body positions to avoid while you recover.
Most people need to avoid driving for at least a few weeks after an SI joint fusion. You should be able to ride in a car or public transit for short distances right away. Your surgeon will tell you when it’s safe to drive.
After surgery, it’s normal to have pain, especially during the first few weeks. Some of it comes from the procedure itself, and some from your body starting to heal.
For pain relief, your surgeon will suggest a combination of:
Your surgeon will tell you what’s safe, how much of each kind of medication you can take and how often to take it.
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Call your surgeon or healthcare provider right away if you experience any of the following symptoms:
Surgeons usually call joint fusion a major surgery. That just means it’s a more complex procedure. SI joint fusion can be done in different ways. Some use small cuts (minimally invasive), while others need bigger cuts (open surgery). Open surgery is usually considered major because more of your body has to be opened up.
The most important thing is choosing the treatment that helps your symptoms. If you’re nervous, talk to your surgeon. They can explain what will happen and answer your questions.
Living with lower back pain can wear you down. When simple tasks start to feel impossible, it’s time to talk to a healthcare provider. If you’ve tried every nonsurgical option and the pain still limits you, SI joint fusion may be worth considering.
In this procedure, your surgeon will permanently join the bones in your affected sacroiliac joint. That can sound overwhelming, but many people feel lasting relief after surgery, often for years.
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You don’t have to make this decision alone. Ask your provider if SI joint fusion might be right for you. They’ll walk you through the risks and benefits, answer your questions and help you find a path toward feeling better.
Back pain can stop you in your tracks. But you don’t have to live like that. Cleveland Clinic is here to help you get moving again.
Last reviewed on 07/23/2025.
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