What are those dimple things that some people have on each side of their spine on their lower back?

Question

What are those dimple things that some people have on each side of their spine on their lower back?

Answer 1

The phrase dimples of Venus refers to the pair of sagittally symmetrical indentations sometimes visible on the human lower back, just superior to the gluteal cleft. The dimples are directly superficial to the two sacroiliac joints, the sites where the sacrum attaches to the ilium of the pelvis.

This term, while informal, is a historically accepted name within the medical profession for the superficial topography of the sacroiliac joints. The Latin name is fossae lumbales laterales ('lateral lumbar indentations'--literally 'ditches' or 'trenches').