Sacroiliac (SI) Joint

The SI Joint

The sacroiliac joint, or SI joint, is one of the most common dysfunctions a chiropractor sees. It involves three large bones, the sacrum, and the two ilium bones on each side of it. It is a hinge with two sides that work independently and in concert with each other. The plane of the hinge is close to being 15 degrees away from center, with a taper to the sacrum.

The SI Joint- Anatomy

The sacrum is a wedge-shaped bone, which, when both legs are on the ground, forms the keystone of an arch, a very stable structure. The geometry of the bone ensures the joint stability, what we call form closure.

When the leg is lifted off the ground, however, the arch becomes unstable, exposed to the shearing of all of our upper body along the plane of the joint. The sacrum, instead of being a stable keystone, now has become a spear point, driving a wedge along the fixed ilium. Muscles and ligaments are needed to hold the bones together into a force closure. The surface where the two bones meet is called the auricular surface, because it looks like a human ear shape. This surface allows motion in rotation forward and back, and if it is irritated, can change its shape to becoming more ridged with time. If this ridging continues, it can lead to a fusion of the two bones together. It can become quite likely that this can occur without intervention, as there are studies to indicate that up to 50 percent of men over the age of 50 have fusion of this hinge.

The SI joint is also subject to forces outside of its joint, namely from the “hamstring muscles”, aka the biceps femoris. The hamstring is often shortened in people who sit for a living, and when that sedentary individual starts to work out the muscle, it can often rotate the rearward, causing pain.

The SI Joint- Diagnosis

The pain from the SI joint is usually located in the hinge space itself, but often the hinge that hurts is the side that IS moving, compensating for the side that isn’t. (ed: it’s usually the case that where it hurts isn’t where the problem is) There are pain referrals for the SI joint, too, namely around the crest of the ilium to the groin, down into the butt and down the leg, usually to the knee. Radiating pain to the foot is usually associated with a disc, but studies show that the pain can extend that far down the leg.

In some patients, pain occurs because of an abnormality of the sacrum bone itself. The sacrum bone is actually a very specialized set of vertebrae (the bones that make up the spine). Before birth, when your body is undergoing development in the womb, several vertebra fuse together to form the sacrum. However, in some people, the bones that make up the sacrum never fuse together. In these cases, two or more of the vertebra that should fuse together remain separated. This creates an odd situation where the SI joint is somewhat malformed, and a false joint occurs. This is sometimes called a “transitional syndrome”. This problem can be seen on x-ray. People who have this syndrome seem to have more problems with their SI joints, as well as back pain that appears to come from that area.

Women are at risk for developing SI joint problems later in life due to childbirth. During pregnancy, female hormones are released that allow the connective tissues in the body to relax. The relaxation is necessary so that during delivery, the female pelvis can stretch enough to allow birth. This stretching results in changes to the SI joints, making them “hypermobile” – extra or overly mobile. Over a period of years, these changes can eventually lead to wear-and-tear arthritis. As would be expected, the more pregnancies a woman has, the higher her chances of SI joint problems. During pregnancy, the SI joints can cause discomfort both from the effects of the hormones that loosen the joints, and from the stress of carrying a growing baby in the pelvis. Many other problems can lead to degenerative arthritis of the SI joints. It is often hard to determine exactly what caused the wear and tear to the joint.

The SI Joint- Treatment

Treatment of the sacroiliac joint is pretty straightforward, and falls into one of two “camps”: One: Increase motion in the SI joint. Essentially it amounts to stretching the hamstring and adjusting the SI joint. Usually, the patient feels about 20 percent reductions in their pain levels on the first day, and 15 percent improvements with each successive visit. About 95 percent of the patients we see experience this.

Two: If increasing motion does not fix your problem, then often we will look to the other extreme, and that is of bracing or stabilizing the hinge. Stabilization of the joint may include muscle strengthening and pelvic stabilization exercises to reduce the movement in a joint that appears to be too loose.

Stabilization can also be accomplished through use of a specific brace called the sacroiliac belt, or an intertrochanteric belt. The belt is usually a non-stretchy, yet comfortable belt, usually made of cotton, worn under the clothes. It wraps around the hips, squeezing the SI joints together. This supports and stabilizes the pelvis and SI joints.

Dr. Carr is very familiar with these cases and has successfully treated SI sufferers with great results. There are no guarantees, however… and some of the treatment must be done at home. Your willingness to do the exercises will make a huge difference in your outcome. If you would like to talk to us further about the SI joint, please feel free to call our convenient downtown location at (206)343-3325.