Bone · Pelvis

Coccyx

Os coccygis

The coccyx is the tailbone — three to five small vertebrae, usually fused, hanging from the bottom tip of the sacrum. It is not a vestige without a job: the pelvic floor muscles, some fibres of the gluteus maximus and the sacrotuberous ligament all attach to it, and it takes a share of your weight whenever you sit leaning back. It is close to the surface, so a fall onto the bottom can leave it tender for a long time.