The sacrum is a bone at the back of the pelvis between the hip bones. A sacral fracture can cause symptoms including lower back and buttock pain, swelling, and reduced bowel and bladder control.

Tarlov cysts, also called perineural or sacral cysts, are pockets of fluid that form around the nerves that make up your spinal cord. Most often, you will find cysts on your sacrum or lower back area.

The nerves get confused and adjust in an unhelpful way; the brain believes the tattletale nerves. Source: Alex Blogoodf/shutterstock. When sensitization is present, it changes how you experience pain.