The coccyx (os coccygis) is the last part of the spine. Read more about structure, function and complaints of the coccyx!


The coccyx (Os coccygis) is the lowest, last section of the spine. It is considered a rudiment of vertebrate tail vertebrae that have regressed over the millennia and grown together into a vertebral block. The coccygeal bone basically has no function in humans anymore, but it can cause discomfort. Read everything important about the tailbone!

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  • What is the tailbone?

  • What is the function of the tailbone?

  • Where is the tailbone?

  • What problems can the coccyx cause?

What is the tailbone?

The coccyx (os coccygis) is the last part of the spine. It consists of four to five vertebrae, which have grown together in adults usually to a uniform bone, which is slightly bent forward. Movements in the coccyx are only possible forwards and backwards.

The individual coccygeal vertebrae are in part only rudiments of the normal vertebral form, that is strongly regressed:

The first vertebra of the coccyx also has a vertebral body, transverse processes and remnants of articular processes pointing upwards to the sacrum. The vertebral arch is missing at the first coccygeal vertebra as well as at all underlying. The vertebral arch are replaced by ligaments. The remaining three to four vertebrae of the coccyx consist only of remnants of the vertebral bodies: They have regressed into round bones of bone.

Fusion of vertebrae

Similarly as at the boundary of the lumbar spine and sacral bone, where the last lumbar vertebrae may be fused to the first sacral vertebra (upper sacralisation), (lower sacralisation) may occur a so-called sacralisation also at the border from the sacrum to the coccyx. These assimilation or transitional vertebrae remain unnoticed and without symptoms in most cases.

The individual vertebrae of the coccyx are interconnected by fibrocartilage. Between the sacrum and the first and second coccygeal vertebrae there is often still an articulated cartilaginous connection (especially in women). In older age, the tailbone usually engores with the sacrum - in men earlier than in women.

The longitudinal ligaments of the spine

The anterior longitudinal ligament of the spine (anterior longitudinal ligament) extending along the entire spine and is firmly connected with the vertebral bodies, to stabilize the spine and limits their backward movement. It loses itself on the front side of the sacrum and reappears only at the coccyx.

The posterior longitudinal ligament of the spine (posterior longitudinal ligament), which is firmly connected to the discs, and together with the front longitudinal band of the stabilization of the spine, the tailbone connects with the sacrum.

What is the function of the tailbone?

The tailbone serves as a starting point for various ligaments and muscles of the pelvis, pelvic floor and hip joints. Since the pelvis is open at the bottom, the ligaments and muscles of this area are important in keeping the organs in place.

The articulated connection between the sacrum and the first two vertebrae of the female coccyx is at a birth of meaning: If the child's head passes through the birth canal, the tip of the tailbone moves by the pressure to about two centimeters rearward and so extends the Pelvic outlet, which facilitates the passage of the child.

Where is the tailbone?

The coccyx (os coccygis) forms the lowest part of the spine, thus following the sacrum.

What problems can the coccyx cause?

As in all sections of the spine, congenital or acquired changes (malpositions, malformations, etc.) may also occur on the coccyx.

A fraction of the coccyx, which occurs especially during a fall on the buttocks, or the rarer dislocation, resulting in that the end piece of the coccyx bends forward. Pain due to fracture or dislocation is particularly noticeable when sitting or sneezing when the pelvic muscles become tense (coccygodynia). Other causes of pain in this area can be a difficult childbirth. Sometimes they are psychogenic as well.

Osteoporosis - as in all bone areas - also leads to coccyx easier to break if the victim falls.

If the connection of the coccyx with the sacrum is bony solidified, this can be a birth obstacle.

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