The iliococcygeus is the posterior and thinner portion of the levator ani muscle group, arising from the tendinous arch of the obturator fascia and the ischial spine, and inserting on the coccyx and the anococcygeal raphe in the midline. It forms the posterior part of the pelvic diaphragm and contributes to pelvic floor support, particularly posteriorly. It is thin and may be deficient or absent in some individuals.
| Origin | Tendinous arch of the levator ani (arcus tendineus levatoris ani) on the obturator fascia |
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| Insertion | Coccyx and anococcygeal raphe, meeting the contralateral muscle in the midline |
| Nerve Supply | Branches from S4 (nerve to levator ani); Inferior rectal nerve (pudendal nerve branch) |
| Blood Supply | Inferior vesical artery; Inferior gluteal artery |
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It forms the posterior part of the pelvic floor, supporting the pelvic organs and helping to resist rises in abdominal pressure.
The iliococcygeus, along with the pubococcygeus and puborectalis, forms the levator ani complex. Differentiating the individual components is important in pelvic floor reconstruction surgery, where the iliococcygeus flap is used as a surgical procedure (iliococcygeus suspension) for apical prolapse repair, attaching the vaginal apex to the iliococcygeus fascia as an alternative to sacrospinous fixation. Tearing of the iliococcygeus origin during childbirth contributes to levator ani avulsion, which is associated with increased risk of pelvic organ prolapse.
Assessed on vaginal or rectal examination as the posterior part of the pelvic floor that can be palpated laterally between the ischial spine and the coccyx.
Traumatic avulsion of the levator ani including the iliococcygeus from the obturator fascia during vaginal delivery, visible on MRI as a defect in the muscle attachment, is strongly associated with the development of pelvic organ prolapse and stress urinary incontinence in later life.
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