The Anatomy of the Coccyx

Table of ContentsView AllTable of ContentsAnatomyFunctionAssociated ConditionsTreatmentFrequently Asked Questions

Table of ContentsView All

View All

Table of Contents

Anatomy

Function

Associated Conditions

Treatment

Frequently Asked Questions

The coccyx can be a source of pain in many people. It is commonly damaged from trauma due to falls and can be the location of idiopathic pain, meaning pain that healthcare providers don’t know the cause of.

The coccyx is the most distal portion of the spine in primates that don’t have tails, including humans.

For the first 20 years of life in humans, the coccyx is made up of separate coccygeal vertebrae, which then fuse together to make a single sphenoid bone that is more commonly known as the tailbone.

Structure

The coccyx is an inverted triangle with the base (wide part) at the top and the apex (pointy end) at the bottom. Even before the fusion of the coccyx is complete, all but the first coccygeal vertebrae are little more than underdeveloped vertebrae that look a bit like nodules of bone rather than independent structures.

There are usually four coccygeal vertebrae that attach to the apex (small, bottom part) of thesacrum. Most of the time, they are referred to as Co1-Co4. It is common and quite natural to be born with as few as three and as many as five coccygeal vertebrae.

Viewed as a single bone, the coccyx resembles a bull’s head. It has two “horns” on top (the base) that are called the coccygeal cornua. The “ears” would be the transverse processes that provide a fulcrum point for articulation with the sacrum.

Location

The coccyx is located at the distal tip of the sacrum and is the most distal portion of the spinal column. The base of the coccyx articulates with the apex of the sacrum. Some articulation is possible between coccygeal vertebrae until they are fused, but they do not move very much.

As the lowest point of the vertebral column and sitting at the bottom of the pelvic girdle, the coccyx acts as one insertion point for the muscles of the pelvic floor, a group of three muscles calledlevator aniat the apex, the coccygeus muscle across the anterior (front) surface, and the gluteus maximus across the posterior (back) surface. It is connected to the sacrum via the sacrococcygeal ligament.

Anatomical Variations

As mentioned above, the coccyx is usually comprised of four coccygeal vertebrae. One study found four coccygeal vertebrae in 76% of healthy coccyges (the plural of coccyx). The coccyx can contain as few as three (13%) or as many as five (11%).

The shape and curvature of the coccyx can vary between individuals and is noticeably different between sexes. The female coccyx is more narrow, less triangular, and more likely to be straight or curved outwardly instead of inwardly.

In more than half of adults (57%), the sacrococcygeal joint (the joint between the sacrum and the coccyx) is fused. The joint between Co1 and Co2 is only fused in 17% of coccyges.

The further along you go on the coccyx, the more common it is for the segments to be fused together.

If humans had tails, the coccyx would have a much more satisfying job. Unfortunately for it, humans don’t, and there are some who say that the coccyx really doesn’t have any function at all.

Several pelvic floor muscles are attached to the coccyx, but every muscle has multiple redundant attachment points. Most of those redundant attachment points are considerably stronger and more stable than the coccygeal vertebrae.

Contraction of those muscles can create enough movement of the coccyx to cause pain in some individuals.

One common treatment for traumatic pain or atraumatic pain that originates in the coccyx for no discernable reason (idiopathic coccyx pain) is for healthcare providers to remove some or all of the coccyx. In patients who’ve had the coccyx surgically removed, there doesn’t appear to be any common side effects, which could suggest that the coccyx truly doesn’t have a function.

tailbone pain causes

The most common condition associated with the coccyx is pain, which is calledcoccydyniaor coccygodynia.

Traumais the most common cause. The location of the coccyx makes it vulnerable to trauma if a person falls to a sitting position. It can become broken or bruised.

In cases of coccydynia, contraction of the pelvic floor muscles can be very painful in the area of the coccyx that is damaged or inflamed. The movement of muscles can lead to movement of the coccyx itself, causing pain.

Because of the number of pelvic floor muscles attached to the coccyx, certain bodily functions, including sex or defecation, can lead topelvic painafter trauma to the coccyx.

Idiopathic painof the coccyx is pain caused for no discernible reason. It is more common in females than in males. This is a diagnosis of exclusion, meaning that it can only be diagnosed after all other possible causes have been ruled out.

Not every coccyx gets completely fused. In some people, the coccyx remains mobile and can continue to move as the person sits and moves. There is some evidence that a rigid coccyx is more likely to cause a certain type of pain due to the fact that it is constantly irritating surrounding soft tissues as the person changes positions.

Sacrococcygeal teratomasare the most common type of neonatal tumor and develop on the sacrum or coccyx.The prognosis for a sacrococcygeal teratoma is very good as long as it is diagnosed correctly and early. Teratomas generally appear when the patient is very young.

Treatment options depend on which condition is causing pain in the coccyx.

Conservative Treatment

In the case of trauma, the most common treatment is a conservative mix of therapies.

It is probably a good idea to give conservative treatment a long leash. It is thought to be successful in 90% of cases of coccydynia.

Surgical Treatment

If a conservative approach is not working, your healthcare provider might suggest surgical removal of the coccyx, known as coccygectomy.

There is not a standard timeline for how long you should wait to consider surgery. Some healthcare providers will consider it in as little as two months if nothing seems to be working. Other healthcare providers might want to continue to try other options for as long as a year.

Even though it is more aggressive than nonsurgical treatment options, complete or partial coccygectomy is considered to be very safe and relatively effective. Patients that have the procedure have good outcomes. About 75% of coccygectomies have a complete reduction of pain.

It is up to you to decide if a 75% success rate is sufficient to undergo surgery. The most common predictor of a poor outcome or failure to relieve pain in all coccydynia patients is whether or not the surgical removal was complete or partial. Evidence suggests that complete coccygectomies lead to better outcomes than partial removal of the coccyx.

Frequently Asked QuestionsEven though we don’t have tails, humans have a tailbone (coccyx) for a couple of reasons. The coccyx is connected to muscles and ligaments that assist in supporting weight while we sit. Additionally, it provides positional support for the anus and assists in giving us control of the bowels.The sacrum is a large bone located at the end of the lumbar vertebrae. It connects to the pelvis to provide support and stabilization. The coccyx is located at the very bottom of the sacrum, and makes up about one-fourth the size of the sacrum.

Even though we don’t have tails, humans have a tailbone (coccyx) for a couple of reasons. The coccyx is connected to muscles and ligaments that assist in supporting weight while we sit. Additionally, it provides positional support for the anus and assists in giving us control of the bowels.

The sacrum is a large bone located at the end of the lumbar vertebrae. It connects to the pelvis to provide support and stabilization. The coccyx is located at the very bottom of the sacrum, and makes up about one-fourth the size of the sacrum.

8 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Tague RG.Fusion of coccyx to sacrum in humans: prevalence, correlates, and effect on pelvic size, with obstetrical and evolutionary implications.Am J Phys Anthropol.2011;145(3):426-437. doi:10.1002/ajpa.21518Woon JT, Perumal V, Maigne JY, Stringer MD.CT morphology and morphometry of the normal adult coccyx.Eur Spine J. 2013;22(4):863-870. doi:10.1007/s00586-012-2595-2Antoniadis A, Ulrich NH, Senyurt H.Coccygectomy as a surgical option in the treatment of chronic traumatic coccygodynia: a single-center experience and literature review. Asian Spine J. 2014;8(6):705-710. doi:10.4184/asj.2014.8.6.705Lirette LS, Chaiban G, Tolba R, Eissa H.Coccydynia: an overview of the anatomy, etiology, and treatment of coccyx pain.Ochsner J; 14(1):84-87.Children’s Hospital of Philadelphia.Sacrococcygeal Teratoma.Ogur HU, Seyfettinoğlu F, Tuhanioğlu Ü, Cicek H, Zohre S.An evaluation of two different methods of coccygectomy in patients with traumatic coccydynia. J Pain Res. 2017;10:881-886. doi:10.2147/JPR.S129198Lirette LS, Chaiban G, Tolba R, Eissa H.Coccydynia: an overview of the anatomy, etiology, and treatment of coccyx pain. Ochsner J. 2014;14(1):84-87.MedlinePlus.Sacrum.Additional ReadingFujisaki A, Shigeta M, Shimoinaba M, Yoshimura Y.Influence of adequate pelvic floor muscle contraction on the movement of the coccyx during pelvic floor muscle training.JPhys Ther Sci. 2018;30(4):544–548. doi:10.1589/jpts.30.544G R, R G, P S, G M, Lu D.Sacrococcygeal Teratoma: Mistreated With Repeated Aspirations. APSP J Case Rep. 2016;7(3):26. doi:10.21699/ajcr.v7i3.422Maigne JY, Pigeau I, Roger B.Magnetic resonance imaging findings in the painful adult coccyx. Eur Spine J. 2012;21(10):2097–2104. doi:10.1007/s00586-012-2202-6Ramieri A, Domenicucci M, Cellocco P, Miscusi M, Costanzo G.Acute traumatic instability of the coccyx: results in 28 consecutive coccygectomies. Eur Spine J. 2013;22 Suppl 6(Suppl 6):S939–S944. doi:10.1007/s00586-013-3010-3

8 Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Tague RG.Fusion of coccyx to sacrum in humans: prevalence, correlates, and effect on pelvic size, with obstetrical and evolutionary implications.Am J Phys Anthropol.2011;145(3):426-437. doi:10.1002/ajpa.21518Woon JT, Perumal V, Maigne JY, Stringer MD.CT morphology and morphometry of the normal adult coccyx.Eur Spine J. 2013;22(4):863-870. doi:10.1007/s00586-012-2595-2Antoniadis A, Ulrich NH, Senyurt H.Coccygectomy as a surgical option in the treatment of chronic traumatic coccygodynia: a single-center experience and literature review. Asian Spine J. 2014;8(6):705-710. doi:10.4184/asj.2014.8.6.705Lirette LS, Chaiban G, Tolba R, Eissa H.Coccydynia: an overview of the anatomy, etiology, and treatment of coccyx pain.Ochsner J; 14(1):84-87.Children’s Hospital of Philadelphia.Sacrococcygeal Teratoma.Ogur HU, Seyfettinoğlu F, Tuhanioğlu Ü, Cicek H, Zohre S.An evaluation of two different methods of coccygectomy in patients with traumatic coccydynia. J Pain Res. 2017;10:881-886. doi:10.2147/JPR.S129198Lirette LS, Chaiban G, Tolba R, Eissa H.Coccydynia: an overview of the anatomy, etiology, and treatment of coccyx pain. Ochsner J. 2014;14(1):84-87.MedlinePlus.Sacrum.Additional ReadingFujisaki A, Shigeta M, Shimoinaba M, Yoshimura Y.Influence of adequate pelvic floor muscle contraction on the movement of the coccyx during pelvic floor muscle training.JPhys Ther Sci. 2018;30(4):544–548. doi:10.1589/jpts.30.544G R, R G, P S, G M, Lu D.Sacrococcygeal Teratoma: Mistreated With Repeated Aspirations. APSP J Case Rep. 2016;7(3):26. doi:10.21699/ajcr.v7i3.422Maigne JY, Pigeau I, Roger B.Magnetic resonance imaging findings in the painful adult coccyx. Eur Spine J. 2012;21(10):2097–2104. doi:10.1007/s00586-012-2202-6Ramieri A, Domenicucci M, Cellocco P, Miscusi M, Costanzo G.Acute traumatic instability of the coccyx: results in 28 consecutive coccygectomies. Eur Spine J. 2013;22 Suppl 6(Suppl 6):S939–S944. doi:10.1007/s00586-013-3010-3

Tague RG.Fusion of coccyx to sacrum in humans: prevalence, correlates, and effect on pelvic size, with obstetrical and evolutionary implications.Am J Phys Anthropol.2011;145(3):426-437. doi:10.1002/ajpa.21518Woon JT, Perumal V, Maigne JY, Stringer MD.CT morphology and morphometry of the normal adult coccyx.Eur Spine J. 2013;22(4):863-870. doi:10.1007/s00586-012-2595-2Antoniadis A, Ulrich NH, Senyurt H.Coccygectomy as a surgical option in the treatment of chronic traumatic coccygodynia: a single-center experience and literature review. Asian Spine J. 2014;8(6):705-710. doi:10.4184/asj.2014.8.6.705Lirette LS, Chaiban G, Tolba R, Eissa H.Coccydynia: an overview of the anatomy, etiology, and treatment of coccyx pain.Ochsner J; 14(1):84-87.Children’s Hospital of Philadelphia.Sacrococcygeal Teratoma.Ogur HU, Seyfettinoğlu F, Tuhanioğlu Ü, Cicek H, Zohre S.An evaluation of two different methods of coccygectomy in patients with traumatic coccydynia. J Pain Res. 2017;10:881-886. doi:10.2147/JPR.S129198Lirette LS, Chaiban G, Tolba R, Eissa H.Coccydynia: an overview of the anatomy, etiology, and treatment of coccyx pain. Ochsner J. 2014;14(1):84-87.MedlinePlus.Sacrum.

Woon JT, Perumal V, Maigne JY, Stringer MD.CT morphology and morphometry of the normal adult coccyx.Eur Spine J. 2013;22(4):863-870. doi:10.1007/s00586-012-2595-2

Antoniadis A, Ulrich NH, Senyurt H.Coccygectomy as a surgical option in the treatment of chronic traumatic coccygodynia: a single-center experience and literature review. Asian Spine J. 2014;8(6):705-710. doi:10.4184/asj.2014.8.6.705

Lirette LS, Chaiban G, Tolba R, Eissa H.Coccydynia: an overview of the anatomy, etiology, and treatment of coccyx pain.Ochsner J; 14(1):84-87.

Children’s Hospital of Philadelphia.Sacrococcygeal Teratoma.

Ogur HU, Seyfettinoğlu F, Tuhanioğlu Ü, Cicek H, Zohre S.An evaluation of two different methods of coccygectomy in patients with traumatic coccydynia. J Pain Res. 2017;10:881-886. doi:10.2147/JPR.S129198

Lirette LS, Chaiban G, Tolba R, Eissa H.Coccydynia: an overview of the anatomy, etiology, and treatment of coccyx pain. Ochsner J. 2014;14(1):84-87.

MedlinePlus.Sacrum.

Fujisaki A, Shigeta M, Shimoinaba M, Yoshimura Y.Influence of adequate pelvic floor muscle contraction on the movement of the coccyx during pelvic floor muscle training.JPhys Ther Sci. 2018;30(4):544–548. doi:10.1589/jpts.30.544G R, R G, P S, G M, Lu D.Sacrococcygeal Teratoma: Mistreated With Repeated Aspirations. APSP J Case Rep. 2016;7(3):26. doi:10.21699/ajcr.v7i3.422Maigne JY, Pigeau I, Roger B.Magnetic resonance imaging findings in the painful adult coccyx. Eur Spine J. 2012;21(10):2097–2104. doi:10.1007/s00586-012-2202-6Ramieri A, Domenicucci M, Cellocco P, Miscusi M, Costanzo G.Acute traumatic instability of the coccyx: results in 28 consecutive coccygectomies. Eur Spine J. 2013;22 Suppl 6(Suppl 6):S939–S944. doi:10.1007/s00586-013-3010-3

G R, R G, P S, G M, Lu D.Sacrococcygeal Teratoma: Mistreated With Repeated Aspirations. APSP J Case Rep. 2016;7(3):26. doi:10.21699/ajcr.v7i3.422

Maigne JY, Pigeau I, Roger B.Magnetic resonance imaging findings in the painful adult coccyx. Eur Spine J. 2012;21(10):2097–2104. doi:10.1007/s00586-012-2202-6

Ramieri A, Domenicucci M, Cellocco P, Miscusi M, Costanzo G.Acute traumatic instability of the coccyx: results in 28 consecutive coccygectomies. Eur Spine J. 2013;22 Suppl 6(Suppl 6):S939–S944. doi:10.1007/s00586-013-3010-3

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Structure#

Location#

Anatomical Variations#

Conservative Treatment#

Surgical Treatment#

Structure

Location

Anatomical Variations

Conservative Treatment

Surgical Treatment