[ is-kee-uhm ]
/ ˈɪs ki əm /
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noun, plural is·chi·a [is-kee-uh]. /ˈɪs ki ə/. Anatomy.
the lower portion of either innominate bone.
either of the bones on which the body rests when sitting.
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Origin of ischium

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


is·chi·ad·ic [is-kee-ad-ik], /ˌɪs kiˈæd ɪk/, is·chi·at·ic [is-kee-at-ik], /ˌɪs kiˈæt ɪk/, is·chi·al, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2022


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-buhros-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


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.

How to use ischium in a sentence

British Dictionary definitions for ischium

/ (ˈɪskɪəm) /

noun plural -chia (-kɪə)
one of the three sections of the hipbone, situated below the ilium

Derived forms of ischium

ischial, adjective

Word Origin for ischium

C17: from Latin: hip joint, from Greek iskhion
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Medical definitions for ischium

[ ĭskē-əm ]

n. pl. is•chi•a (-kē-ə)
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.ischial bone

Other words from ischium

is′chi•adic (-ădĭk) adj.ischi•al (-əl) adj.is′chi•atic (-ătĭk) adj.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Scientific definitions for ischium

[ ĭskē-əm ]

Plural ischia
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.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.