Coccygeus muscle
The coccygeus muscle is posterior to levator ani and anterior to the sacrospinous ligament in the pelvic floor.It arises by its apex from the spine of the ischium and sacrospinous ligament.[3][4] It is inserted by its base into the margin of the coccyx and into the side of the lowest piece of the sacrum.[3][4] In combination with the levator ani, it forms the pelvic diaphragm.[8] This article incorporates text in the public domain from page 424 of the 20th edition of Gray's Anatomy (1918)