Causes of coccydynia

The coccyx is the very bottom portion of the spine. It represents a vestigial tail (hence the common term "tailbone") and consists of four or more very small bones fused together. The coccyx articulates with the sacrum through a vestigial disc, and is also connected to the sacrum with ligaments (see Figure 1).

It is not clearly understood which portions of the anatomy can cause coccyx pain. Either the ligaments or the vestigial disc may be a cause of pain and, rarely, a primary bone tumor or soft tissue tumor can cause pain.

It is thought that the condition is more common in women because:

• In women the coccyx is rotated and faces backward, which makes it more susceptible to trauma.

• Women have a broader pelvis, which means that sitting places pressure not only on their ischial tuberosities ("butt bone") but also on the coccyx. (Men tend to sit only on their ischial tuberosities without a lot of pressure applied to the coccyx.)

• Childbirth is a common cause of the condition

The two most common causes of coccydynia are:

• Local trauma. A fall on the tailbone can inflame the ligaments or injure the coccygeal attachment to the sacrum

• Childbirth. During delivery, the baby’s head rides over the top of the coccyx and can injure the same structures.