Unlocking the Mystery of Lower Back Pain: The Role of the SI Joint

Back pain is a common ailment, and among its many causes, sacral-iliac joint dysfunction is a significant but often overlooked contributor. The sacral-iliac (SI) joint connects the sacrum, a triangular bone at the base of the spine, to the iliac bones of the pelvis. This joint plays a crucial role in supporting and stabilizing the pelvis during movement. When the SI joint becomes dysfunctional, it can lead to discomfort and pain.  

The SI joint’s primary function is to absorb shock between the trunk and the legs while providing stability to the pelvis. If the SI joint is out of alignment or not functioning correctly, it can disrupt the normal biomechanics of the lower back and pelvis. 

 Several factors can contribute to SI joint dysfunction: 

•  Pregnancy: During pregnancy, hormonal changes can make the ligaments around the SI joint can make them more lax.  Changes in the center of gravity put more pressure on the ligaments. The growing uterus and shifting weight can alter the pelvis’s alignment, leading to SI joint pain. 

•  Biomechanical Imbalances: Poor posture, pelvic alignment changes, leg length discrepancies, or abnormal gait can place additional stress on the SI joint. Over time, these imbalances can contribute to joint dysfunction. Chronic misalignment can shear the joint, contributing to inflammation, disrupting the joint’s normal function.  

• Muscle Imbalances: Weak or tight muscles around the pelvis and lower back can impact the SI joint. For example, tight hip flexors or weak gluteal muscles can increase the pull on the joint and decrease its stability contributing to pain. 

The symptoms of SI joint dysfunction can vary, sometimes making it tricky to diagnose. Common symptoms include:   

• Lower Back Pain: Pain is often felt in the lower back, especially near the dimples above the gluteal muscles. 

• Hip Pain: Discomfort may radiate into the hips and buttocks. 

• Radiating Pain: Pain can sometimes radiate down the legs, rarely past the knee, mimicking sciatic pain. 

• Stiffness: The general region may feel stiff, particularly after periods of rest or inactivity.  

Treatment for SI joint dysfunction should include a consultation with a physical therapist.  Pelvic floor physical therapy is uniquely qualified to treat SI joint pain because of our education in orthopedic and pelvic floor anatomy and biomechanics.  We can look at not just how the low back and hips are affecting the SI joint, but also how the tailbone and pelvic floor muscles are as well.  From there we can develop the best exercise program to give your SIJ stability and mobility to decrease pain.  

-Jennifer Cumming, PT, MST, CLT, WCS