What is the SI Joint?


The SI joint, short for sacroiliac joint, is a large synovial joint that connects the sacrum and the ilium of the pelvis. There are 2 of them, one on each side of the sacrum. When normal they have very strong ligaments and are able to absorb significant bodily shock.


How does SI Joint pain occur?


Location of the sacroiliac (SI) joint

Most people don’t realize that up to 25% of chronic lower back pain is caused by the sacroiliac joint. This can be due to a traumatic even such as a car accident, wear and tear degeneration, or inflammation called sacroiliitis. One may have too much motion (hypermobility) or too little (hypomobility).


The resulting pain may be dull or sharp, and possibly become referred to the low back, groin, buttocks or thighs. Movements may exacerbate pain, and one may experience muscle spasm as a protective mechanism.


What are the best treatments?


SI joint fusion with titanium rodsOnce a physician identifies the SI joint as the source of the patient’s pain, most of the time it can be treated with nonsurgical methods. This may include NSAIDS, physical therapy or intraarticular injections.


Should these treatments be inadequate, the SI Joint Fusion procedure may become necessary. There are several different techniques available to achieve this fusion. These may involve placing compression screws across the joint, or titanium rods. The implant placement prevents the SI joint from moving, so the individual’s pain will diminish.


Along with the implant placement, bone graft may be included to help facilitate the fusion occurring. The procedure takes about an hour, and is performed through a tiny incision.


What are the outcomes of an SI fusion?


To date there have been over 20,000 SI fusions performed in the US, and research has been able to follow outcomes for over 5 years. One large study showed that 82% of patients said they were satisfied and would undergo the same procedure again after five years!



Rudolf* et al., Sacroiliac joint arthrodesis-MIS technique with titanium implants: report of the first 50 patients and outcomes. Open Orthopaedics Journal. 2012,6:495-502.