Coccygeus

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

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

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