The Sacro-Iliac Joint: the base of the spine

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The sacroiliac joint is located at the base of the spine. Specifically, it describes where the sacrum (the triangular piece of bone at the base of the spine) meets the ilium (part of the pelvis). Much of the time people refer to the sacroiliac joint as the SI joint. Throughout this article, I will be referring to the SI joint in the singular. But in the back of your mind, know that there are 2 – one on either side of the sacrum.Support for the SI Joint, or not!

The SI joint shares some similarities with other joints, however, there are some important differences that you need to be aware of. Like most joints, the SI joint is supported by ligaments. They are located in the front and back of the joint, as well as at the lower portion of the sacrum. Unlike most joints, there aren’t any muscles that directly cross over the SI joint to support it. Therefore, direct support comes from the ligaments. These ligaments help to keep the sacrum in place.

Sometimes, joints and ligaments can experience injury. When this happens at the SI joint, the little movement that occurs naturally, may become too great (hypermobile) causing the joint to become unstable, or the movement may become too limited (hypomobile) causing the joint to become fixed.

For example, hypermobility commonly occurs after pregnancy. During pregnancy the hormone relaxin causes the ligaments to become more lax, permitting more movement at the joint. If the laxity of the ligaments is excessive the joint itself can become hypermobile and unstable.What does this have to do with Yoga?

Hyper or hypo mobility at the SI joint can be a contributing factor in back and butt pain, and these symptoms are sometimes the catalyst for people coming to Yoga.

Keep the following in mind

  • Because of its placement in the body, the SI joint acts as a bridge in transmitting the forces from the upper body to the pelvis, hips and legs.
  • Even though there are no muscles directly supporting the joint, the muscles that attach to the sacrum or the ilium will have an indirect effect on the functioning and balance of the joint. These include the hamstrings, piriformis, gluteus maximus, and erector spinae. If these muscles are tight or weak they can affect the functioning of the SI joint.
  • Because there are 2 SI joints, the joint mobility or strain can occur more on one side than the other.

    • If you have pain as the result of the SI joint

  • Seek out a manual physiotherapist or chiropractor to ensure that Yoga moves are okay for your body at this time.
  • Seek out a Yoga instructor who has a great eye for alignment and can help you feel the proper pelvic and lumbar spine alignment. Proper alignment will help alleviate strain, as well as strengthening or stretching muscles which, out of habit, are out of balance.