First, it’s key to understand that the SI joint connects the pelvic bone (ilium) to the lowest part of the spine (sacrum). There are two SI joints. Each is located on either side of the sacrum. SI joints are small and very strong, providing structural support and stability. They function as shock absorbers for the pelvis and the low back, dispersing the forces of the upper body. Whenever an SI joint is irritated or injured, the resultant joint dysfunction may cause pain in the lower back and legs.
Two types of changes from normal motion can cause problems
Those changes are either too much movement (hyper-mobility) or too little movement (hypo-mobility)
Abnormal motion from work/sports can directly injure the joints via stretching/straining the primary SI ligaments
Any of these changes in joint mobility may lead to pain, as well as spasm in the supporting back and pelvic muscles
SI joint dysfunction may also result from direct trauma, such as injuries associated with a motor vehicle accident
Or an injury from something as simple as a fall on the buttocks or a missed step when descending stairs
Symptoms of SI joint dysfunction are often hard to distinguish from other types of low back pain. In most cases, there is a confusing pattern of back and pelvic pain that mimic each other, making diagnosis of SI joint dysfunction very difficult. The most common symptoms of SI joint dysfunction include:
- Low back pain
- Buttock pain
- Thigh pain
- Difficulty sitting in one place for too long due to pain
Procedural treatment for SI joint disease can include cortisone injections into the sacroiliac joints. There is also a procedure that can ablate or burn the nerves responsible for communicating pain signals from the SI joint to the brain. Regenerative injections including platelet-rich plasma (PRP) injections are also being used experimentally to provide a healthier environment to promote healing.