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A doctor pointing to the Sacroliac Joint with a pen on a bone sculpture.

Sacroiliac Joint (SI Joint)


The sacroiliac joint is an essential component for energy transfer between the legs and the torso. Like any other joint in the body, the SI joint can be injured and/or undergo degeneration. When this happens, people can feel pain in their buttock and sometimes in the lower back, hips, and legs. This is especially true while lifting, running, walking, or even lying on the involved side.

The sacroiliac joint (SI joint) is located in the pelvis; it links the iliac bones (pelvis) to the sacrum (lowest part of the spine above the tailbone).

Do you have SI Joint Pain?

The SI joint can be a significant cause of lower back pain. Clinical publications have identified the SI joint as a pain generator in 15-30% of chronic lower back pain patients.14 In addition, the Sl joint is a pain generator in up to 43% of patients with continued or new onset lower back pain after a lumbar fusion.

Symptoms may include:

  • Lower back pain
  • Sensation of low extremity: pain, numbness, tingling, weakness
  • Pelvis/buttock pain
  • Hip/groin pain
  • Feeling of leg instability (buckling, giving way)
  • Disturbed sleep patterns due to pain
  • Disturbed sitting patterns (unable to sit for long periods, sitting on one side)
  • Pain going from sitting to standing

Explore whether iFuse is right for you

The first step to finding out if you’re a candidate for the iFuse procedure is making an appointment with an iFuse-trained surgeon to discuss your options.

Making a Diagnosis

A variety of tests performed during physical examination may help reveal the SI joint as the cause of your symptoms. Sometimes, X-rays, CT-scan or MRI may be helpful in the diagnosis of SI joint-related problems because they can rule out other common sources of pain-such as your lumbar spine or hip joints. It is also important to remember that other conditions (like a disc problem) can co-exist with SI joint disorders. The most relied upon method to accurately determine whether the SI joint is the cause of your lower back pain symptoms is to inject the SI joint with a local anesthetic.

This diagnostic injection will be performed under either X-ray or CT guidance to verify accurate placement of the needle in the SI joint. If your symptoms decrease by at least 50%, it can be concluded that the SI joint is either the source of or a major contributor to your lower back, hip, or pelvic pain. If the level of pain does not change after SI joint injection, it is less likely that the SI joint is the cause of your pain.

Treatment Options

Once the SI joint is confirmed as the cause of your symptoms, treatment can begin. Some patients respond well to physical therapy, use of oral medications, or injection therapy. These treatments are often performed repetitively, and frequently symptom improvement using these therapies is temporary. If non-surgical treatment options have been tried and do not provide long-term relief, your surgeon may consider other options, including the minimally invasive iFuse procedure.

Hear from an iFuse Patient – Cara’s Story

“iFuse gave me my life back.”

Cara spent 10 years with debilitating SI joint pain that she had to plan daily activities around. Whether she wanted to go grocery shopping, do laundry, or spend time with loved ones-her pain would often get in the way. Hear how S1 joint fusion with the iFuse Implant System made a difference in her life.

Play Video about PSO - iFuse Testimonial - Cara

Lower Back Pain and Sacroiliac Joint Pain

In 15-30% of cases, chronic low back pain may not be due to an issue in the low back-it may be caused by an issue with the sacroiliac joint, but without appropriate diagnostic evaluation and interpretation by a health provider trained to evaluate the SI joint, the source can be missed.

Defining Lower Back Pain

“Lower back pain” is a term that is broadly used to describe pain that could have various causes including structures in the lower back, the buttocks or the pelvic region. Is your “low back pain” truly coming from your lower back?

Low back pain is a common issue that affects many people during their lifetime. There are many structures in the lower back and pelvic area that can cause pain. Most commonly, people with low back pain believe that the lumbar spine is the cause of their pain. Occasionally, hip problems can cause pain that is sometimes confused with low back conditions. Another common cause of low back pain symptoms can be the sacroiliac joint. Si joint dysfunction can be a significant contributor to pain in the lower back, pelvic region, buttocks, or legs.

Sacroiliac Joint Dysfunction FAQs

The function of the SI joint is to transfer weight and forces due to movement from your legs, through the pelvis to your upper body and vice versa-acting as an anatomical shock absorber to protect the spine during activity. The primary role of the SI joint is to provide stability for the pelvis and to bear the load of the upper body.

A sacroiliac joint exam includes:

  • Consideration of a patient's health history and symptoms,
  • Asking the patient to point to where it hurts (Fortin Finger Test),
  • Physical examination, including provocative tests (stressing the joint in an attempt to recreate the pain),
  • Diagnostic injections (injecting anesthetic into the joint to see if the pain goes away).

The iFuse Procedure is a minimally invasive surgery that stabilizes and fuses the SI joint. Typically, a surgeon places three small triangular titanium implants across the joint, and the triangular shape and strength of the implant resists movement and rotation of the joint. iFuse is the only device for treatment of SI joint dysfunction that is backed by significant published clinical evidence, including two randomized controlled trials

Trauma and degeneration are two leading causes of SI joint dysfunction. Sacroiliac joint trauma can occur during motor vehicle accidents, falls on the buttocks, lifting and/or twisting, pregnancy and childbirth. Sacroiliac joint degeneration can occur as a result of previous lumbar spine surgery, stresses to the SI Joint due to leg length differences, osteoarthritis, and prior infection of the SI joint.

  • Lower back pain (below L5)
  • Sensation in lower extremity; pain, numbness, tingling, weakness
  • Pelvis/buttock pain
  • Hip/groin pain
  • Feeling of leg instability (buckling, giving way)
  • Disturbed sleep patterns due to pain
  • Disturbed sitting patterns (unable to sit for long periods, sitting on one side)
  • Pain when going from sitting to standing

Prospective patients should speak to their doctor and can learn more about sacroiliac joint dysfunction, treatment options, and the iFuse Implant System via SI-BONE's website, www.si-bone.com. For indications, risks, and safety information about the iFuse Implant System, visit www.si-bone.com/risks.

Sacroiliac Joint (SI Joint) Treatment Physicians

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