ischium

[ is-kee-uhm ]

noun

, Anatomy.

, plural is·chi·a [is, -kee-, uh].

1. the lower portion of either innominate bone.
2. either of the bones on which the body rests when sitting.

ischium

/ ˈɪskɪəm /

noun

1. one of the three sections of the hipbone, situated below the ilium

ischium

/ ĭs′kē-əm /

, Plural ischia

1. The lowest of the three major bones that constitute each half of the pelvis, distinct at birth but later becoming fused with the ilium and pubis.

Derived Forms

• ˈischial, adjective

Other Words From

• is·chi·ad·ic [is-kee-, ad, -ik], is·chi·at·ic [is-kee-, at, -ik], ischi·al adjective

Word History and Origins

Origin of ischium¹

1640–50; < Latin < Greek ischíon hip-joint

Word History and Origins

Origin of ischium¹

C17: from Latin: hip joint, from Greek iskhion

Example Sentences

In the pelvic girdle the ilium corresponds to the scapula, the ischium to the coracoid, the pubis to the clavicle.

From Project Gutenberg

They are unknown in any other existing animals, unless present in Crocodiles, in which ischium and pubis are always undivided.

From Project Gutenberg

There is some difference in the pubis and ischium which is more conspicuous in form than in direction of the bones.

From Project Gutenberg

The pubis is slender, and the ischium is elevated and robust.

From Project Gutenberg

The body of the ischium in this case was fractured and a rent in the bladder was caused by a sharp projecting piece of bone.

From Project Gutenberg

More About Ischium

What is ischial tuberosity?

Ischial tuberosity is the name for the part of the pelvis that supports a person while sitting.

How to pronounce ischial tuberosity

[ is-kee-uhl too-buh–ros-i-tee ]

Where did ischial tuberosity come from?

Ischial tuberosity is an anatomical term for the V-shaped bone at the bottom of the pelvis that makes contact with a surface when a person is sitting down, hence their common name of sit bone or sitting bones.

Forming one of the main parts of the pelvis, the ischial tuberosity is the attachment site for a series of ligaments and muscles, notably the hamstrings, which support the body while sitting. It is located directly beneath the ischial spine (the very bottom of your spine near the hip bones) and, when standing, is covered by the gluteus maximus (the butt muscles).

Emerging in the 1800s, ischial is the adjective form for ischium, a 17th-century anatomical term generally used for the “bones on which the body rests when sitting.” Tuberosity indicates a slight ridge or roundness on the surface of the bone—think protuberance—where muscles attach. Also appearing in the 17th century, tuberosity comes from the Latin base, tuber, literally meaning “bump” or “swelling.”

Ischial tuberosity is typically due to an inflammation of the surrounding muscles. The cause of this pain usually stems from repetitive movements or positions, such as sitting for too long or from overextending muscles through excessive exercise.

The Western yoga community commonly calls ischial tuberosity pain “yoga butt.” Yoga involves many forward bends, which can overextend the hamstrings and lead to strains around the ischial tuberosity, a concern among very flexible yoga practitioners. Remedies include rest and the immediate halt of any activities. Severe pain, of course, should always be diagnosed by a certified physician.

How to use the term ischial tuberosity

Ischial tuberosity typically comes up in technical contexts, used by anatomical scientists and medical professionals, especially orthopedic doctors. Physical therapists and sports-medicine professionals, as well as their patients, also use ischial tuberosity in their practice.

Since the ischial tuberosity projects on both sides of the pelvis, some people refer to them together as the ischial tuberosities.

In colloquial contexts, as noted, people refer to the ischial tuberosity as the sit bone(s), especially when speaking to little kids, as in “Sit down on your sit bones, please.”

More examples of ischial tuberosity:

“If you place your hands behind your knee, you can feel the hamstring attachments as firm, bone-like tendons — one on the outside and two on the inside of the knee. On the other end, the hamstrings also attach to the ischial tuberosity (sitting bones) of the pelvis.”
—Eva Norlyk Smith, HuffPost, December 2017

Note

This content is not meant to be a formal definition of this term. Rather, it is an informal summary that seeks to provide supplemental information and context important to know or keep in mind about the term’s history, meaning, and usage.