Also known as tailbone, coccyx is the final segment of the vertebral column. It comprises of four small vertebrae that are fused together to form a single small triangular bone. Coccyx is attached to the sacrum by the sacrococcygeal symphysis, which is a fibrocartilaginous joint. It permits only limited movement.


As described above, it is a small triangular bone formed by the fusion of four coccygeal vertebrae. The coccygeal vertebrae consist of body only. However, the first vertebra possesses a rudimentary traverse process and cornua. Cornua are the remains of the pedicels and the superior articular processes of this vertebra. They project upward to articulate with the sacral cornua.

The anterior surface of the coccyx is slightly concave and is marked with transverse grooves that indicate the junction of the vertebrae. The posterior surface is convex and has similar transverse grooves.

Function of coccyx:

It is believed that the coccyx is remnant of vestigial tail. But it is not useless in the body. It provides attachment to various important muscles, ligaments and tendons. Additionally, it is also a component of the weight bearing structure during sitting position.