What is the Sacroiliac Joint?

The sacroiliac (SI) joint is the largest synovial joint in the body and is located within the pelvis.  There are two SI joints between the sacrum, the largest bone of the spine,  and the ilium, or wings of the pelvis on either side.   Although the joint does not move a great deal, it does allow for some flexibility in the pelvis and can become painful with injury or degeneration.  In fact,  SI joint pain represents approximately 15% of all types of back pain.  Most of the time, the SI joint performs its function of keeping the pelvis flexible and does not cause any other trouble.   However, it is only through certain circumstances that this joint becomes painful.   SI joint pain can easily be mistaken for hip pain or back pain or lower back pain.

Who gets SI Joint Pain?

SI joint pain can occur in several patient populations.  The most common patient to get this type of pain is one who has arthritis, especially older people.   Those who have  fusions of the  lumbar spine can develop pain in the SI joints, because the force of movement or twisting of the spine is transmitted through the fused lumbar vertebrae to the SI joints.  For the same reason, those suffering from ankylosing spondylitis may develop SI joint pain.   Interestingly, pregnant women are at risk for SI joint pain because the hormones of pregnancy loosen the muscles and ligaments of the pelvis for passage of the baby.  In some cases, the joint loosens too much and causes pain.  In addition, after pregnancy, the joint may not return to its normal tightness, and this can cause pain that lasts after the baby is born.  Next, Athletes are in particular danger of SI joint problems because of the demands they make on their body.   Finally,  SI joint pain is seen due to trauma after motor vehicle accidents.

What is SI Joint Pain?

The pain that arises from SI joint dysfunction is usually experienced as a sharp ache in the buttock area. However, it can be perceived as lower back pain or pain in the hip areas.  Sometimes pain coming from the SI joint can feel as though it is spreading down the leg like sciatica.    The widespread nature of  SI pain and closeness to other structures  that can also cause pain make SI joint pain difficult to diagnose.  SI joint pain is often experienced as pain in the buttock/lower back/hip with sitting.   When the pain is very severe, those suffering from SI joint pain will be often be unable to sit on one of their buttock cheeks. Since the SI joint  is close to the hip joints and lower spine, pain coming from the SI joint can be easily mistaken for hip pain or a problem within the lower back lumbar spine resulting in lower back pain.  Certain maneuvers on physical exam can be suggestive of pain that is from the SI joint.  XRays of the lower back, pelvis, and hip can help point to one of these areas such as lower back pain as being the source of the pain.   Often those suffering from arthritis in the back or hip may also be suffering from arthritis of the SI joint.  One of the most definitive ways to make the diagnosis of SI pain is to have the patient undergo a diagnostic injection of the SI joint with local anesthetic.  If the pain disappears or decreases considerably after the injection, then the source of the pain can be pinpointed to the SI joint.

Treatment of SI joint Pain

The usual treatment for sacroiliac joint pain is a course of non-steroidal anti-inflammatory medications, such as ibuprofen or naproxen, and focused physical therapy.  In some cases, chiropractic care may be helpful to realign the joints of the spine and pelvis.   A special belt worn around the pelvis can help provide additional support to the SI joint and diminish pain.

Pain management physicians are vital in the treatment of SI joint pain.  Not only can they diagnose SI joint pain, but also they can treat it.  SI joint injections must be done with image guidance such as XRay to assure accuracy of the injection.   A steroid injection into the SI joint is a powerful way to decrease inflammation, and therefore pain.  If steroid injections are not successful in controlling pain for more than a few weeks, longer term pain relief can be achieved by radiofrequency ablation of the nerves that supply the back of the SI joint and  is an excellent treatment option.  When the sensory nerves that supply the SI joint are cauterized, the pain signal from the joint can not be transmitted.   There is some localized discomfort after this procedure, which is treated with ice and over the counter pain relievers.  Full relief is expected in 6-8 weeks from the time of the procedure.   The above procedures often successfully manage SI  pain without resorting to surgery.

Very rarely do patients need surgical intervention for SI pain.  The primary surgical option is a fusion of the ilium to the sacrum, thus, taking the flexibility out of the pelvis.  Usually, less invasive options must be exhausted before a fusion is considered