Sacral and back dimples are congenital, which means you are born with them.‌ Sacral dimples show up in 1.8% to 7.2% of newborn babies. Doctors usually use ultrasound to find out if the dimple is ...

Their MRIs reveled the same diagnosis: a sacral stress fracture, or a hairline crack in the large, triangle-shaped bone at the base of the spine.