Sacroiliac Joint Pain  

The sacrum is the lower portion of the spine where several vertebrae are fused together. The sacrum is a triangular shaped bone that has a joint on either side with the ilium, the back part of the pelvis. The pubic rami, the front part of the pelvis, fit together in the front forming the pubic symphysis. The sacroiliac joints are L shaped in contour with a shorter upper and longer lower arm. Normally the sacroiliac joint is configured in such a way that the bones have an interlocking structure, which assists in keeping them properly aligned. In some cases the opposing joint surfaces are quite flat. 

This type of joint is much less stable and can lead to a shearing or sliding malalignment. Some sacroiliac joints reverse the normal concave-convex ‘locking’ relationship, which can lead to rotational malalignment. The variation in joint configuration results in a corresponding variation in integrity. This means that some people are more susceptible to SI joint pain because the joints are inherently weaker or more prone to malalignment.

There are several different factors that can cause SI joint pain and dysfunction. One of the most common causes is an injury. The injury can come from a direct fall on the buttocks, a motor vehicle accident or a sports related trauma. The force from these injuries can strain the ligaments around the joint. Tearing of these ligaments can lead to hypermobility in the joint. This excess motion and lack of stability is thought to be the main cause behind sacroiliac joint dysfunction.

Pregnancy may also be a factor in the development of SI joint pain. Women secrete the ‘relaxing’ hormone during pregnancy. This hormone allows the connective tissues in the body to relax. The relaxation is needed so the pelvis can stretch enough to allow the baby to pass during labor. This stretching may affect the SI joints causing them to become hypermobile. The more pregnancies a woman has, the more chance she has of developing SI joint pain.

Leg length discrepancies may also play a role in sacroiliac joint dysfunction. If a person has one leg that is shorter than the other, the abnormal alignment may end up causing SI joint pain or malalignment issues.

Often, an exact cause leading to SI joint pain cannot be found. The joint simply becomes painful, and the patient and their local physician do not have an answer as to why the joint has become troublesome. It takes a trained health care provider to accurately diagnose and treat sacroiliac joint pain.