What is the Sacro-Iliac Joint?

In an ongoing series of posts, Queen Street Chiropractic Centre will be attempting to shed some light on the myriad variety of factors and structures that can contribute to lower back pain.  The following is a discussion of the sacro-iliac joint.

The sacro-iliac joint is a structure which contributes to forming the pelvis and acts as a transitional area between your lower/lumbar spine and pelvic region.  If you want to know where your sacro-iliac joint lies, follow along with this simple technique.  Feel the small of your back right in the middle of your spine.  Now, exerting a mild pressure, slide from the middle of your back to either the left or right side. 

Do you feel an area that feels like a knuckle?

Now exert a little more pressure….does it hurt?

Chances are that you have found your sacro-iliac joint, and if it is sore then chances are it is time to visit Queen Street Chiropractic Centre.

But what is the sacro-iliac joint?

The sacro-iliac joint is formed from two bones in the pelvis.  The Sacrum is a bone which looks like an inverted triangle and is a key component of the spine.  The Ilium is a broad, flat bone which is easily felt along the flank of our torso and is what most people associate with the term “hip”.  The sacro-iliac joint is the structure that joins these two bones together, and it is one of the very strongest joints of the body.

The sacro-iliac joint can best be described as a structural joint, and the stresses it has to withstand are truly extraordinary.  Every transfer our body goes through over the course of the day (sitting to standing, laying down to sitting up and vice versa and so on) exerts pressure on the sacro-iliac joint.  Also, the sacro-iliac joint is pivotal in providing the reciprocal gait necessary to walking upright (it makes our hips sway, if you will).

In terms of anatomical structure, the sacro-iliac joint is truly a marvel of biomechanics.  It is a boot-shaped joint that is unique in that it is composed of two types of joint complexes.  There is an intramembranous joint structure (think of this as a “Velcro” joint that sticks the two bones together), and also there is a synovial component to the joint (which is the same type of joint as the knees/shoulders/hips and provides for free range of motion.

The sacro-iliac joint also has an extensive network of muscular attachments involved in its motions and movements.  These muscles are arranged in several layers, from superficial to deep, and range from the large and powerful gluteus maximus to smaller intrinsic muscles such as the obturator externus and internus.  All of these muscles act in synergy to produce movement of the pelvis and strengthen the area.

Lastly, the sacro-iliac joint is closely associated with the nerves exiting the lumbar region of the spine.  These nerves arise from the spinal cord, exit the lower back through the vertebra of the lumbar spine, and run over and around the sacro-iliac joint on their way to provide sensation and motor control to the legs.

Injury to the sacro-iliac joint will present as a deep, achy or sharp pain on the right or left side of the small of the back.  The pain in the lower back will often drift into the buttock area, and may even cause pain down the back of the leg to the knee.  Pain will be increased with motion of the lower back, usually getting up from bed in the morning and moving from sitting to standing and vice versa will provoke the pain.

The Doctors at Queen Street Chiropractic Centre are well experienced in dealing with this type of injury, and have a variety of techniques to employ in the treatment of sacro-iliac dysfunction. 

Feel free to book an appointment today at Queen Street Chiropractic Centre.