Coccyx - Definition and Overview

The coccyx, commonly referred to as the tailbone, is the final segment of the human vertebral column, of three to five (usually four) fused vertebrae (the coccygeal vertebrae), below the sacrum. It is attached to the sacrum in a fibrocartilaginous joint, which permits limited movement between them.

The coccyx is regarded as vestigial in humans, meaning it no longer serves major functions it did in ancestor species of humans. (Those included supporting a tail and accommodating its nerves.) It does provide an attachment for muscles, such as the gluteus maximus, and also serves as something of a shock absorber when the person sits down, although forceful impact can cause damage and subsequent bodily pains.

The coccygeal bones fuse as a person ages.

Injuring the coccyx can give rise to a condition called Coccydynia.

See also

• Bone terminology
• Terms for anatomical location