Coccygeus
Coccygeus is a small muscle from the ischial spine to coccyx that reinforces and supports the pelvic floor.
The coccygeus muscle, also known as the ischiococcygeus, is a small triangular muscle located in the posterior part of the pelvic diaphragm. It lies posterior to the levator ani and forms part of the pelvic floor. Although smaller and less functionally significant than the levator ani, the coccygeus plays a supportive role in maintaining pelvic floor integrity and reinforcing the posterior pelvic outlet. It also assists in stabilizing the sacroiliac joint and flexing the coccyx.
Structure
The coccygeus is a paired skeletal muscle. Each muscle originates from the ischial spine and inserts on the lateral aspects of the lower sacrum and coccyx. It blends with the sacrospinous ligament and may be difficult to distinguish from it during dissection.
Attachments
| Region | Attachment |
|---|---|
| Origin | Ischial spine |
| Insertion | Lateral borders of the sacrum and coccyx |
Location
The coccygeus muscle lies posteromedial to the ischial spine, just posterior to the iliococcygeus part of the levator ani. It forms the posterior margin of the pelvic diaphragm and lies adjacent to the sacrospinous ligament, with which it is often fused. It is located near the sacroiliac joint and the greater sciatic foramen.
Function
- Pelvic Floor Support: Reinforces the pelvic diaphragm and helps support pelvic organs from below
- Stabilization: Helps stabilize the sacrum and coccyx, particularly during movement of the pelvic floor
- Coccyx Flexion: Assists in pulling the coccyx anteriorly after defecation or childbirth
- Posterior Outlet Closure: Works with levator ani to close the posterior pelvic outlet and resist intra-abdominal pressure
Innervation
- Nerve to coccygeus (S4–S5): A direct branch from sacral nerves that supplies motor function
Relations
| Structure | Relation |
|---|---|
| Sacrospinous ligament | Closely associated; coccygeus often fused with this ligament |
| Levator ani | Anterior to coccygeus; forms rest of the pelvic diaphragm |
| Rectum | Anterior to coccygeus, especially near the anorectal junction |
Clinical Significance
- Pelvic Floor Dysfunction: Though rarely isolated, coccygeus weakness may contribute to pelvic floor instability and organ prolapse
- Coccydynia: Chronic tailbone pain may involve spasm or strain of the coccygeus or its surrounding tissues
- Obstetric Trauma: May be stretched or torn during childbirth, especially with excessive coccyx movement
- Surgical Relevance: Awareness of coccygeus anatomy is important during sacrospinous ligament fixation surgeries for prolapse repair
Last updated on May 10, 2025