coccygeus muscle, muscle of the lower back that arises from the ischium (lower, rear portion of the hipbone) and from the ligaments that join the spinal column and the sacrum (triangular bone at the base of the spine). It is attached to the lower sacrum and the coccyx (tailbone). In humans its major function is to support the pelvic viscera, especially in the female. It also raises the coccyx.