Ligaments of The Sacrum

The sacrum, at the base of the vertebral column, is wedged between the coxal bones of the pelvis and is united to them by fibrocartilage at the "sacroiliac joints." The weight of the body is transmitted to the legs through the pelvic girdle at these joints. The fibrocartilage at the front of the sacrum, which joins it to the ilium is called the "anterior sacroiliac ligament"; at the back, it is called the "posterior sacroiliac ligament." The coccyx, or tail bone, is attached by ligaments to the margins of the sacral hiatus (opening at the tip of the sacrum). These ligaments are called the "anterior" and "posterior sacrococcygeal ligaments." The "sacrospinous ligament" is a thin, triangular sheet attached by its broad base to the lateral margins of the sacrum and coccyx, where its fibers are intermingled with those of the intrapelvic surface of the "sacrotuberous ligament," and by its apex to the spine of the ischium. The sacrotuberous ligament is a broad, flat fan-shaped complex of fibers stretching from the lower back spine of the ilium, the 4th and 5th transverse tubercles and the caudal part of the lateral margin of the sacrum and coccyx to the inner margin of the tuberosity of the ischium. The "iliolumbar ligament" connects the lower lumbar vertebra process to the ilium (the largest portion of the coxal bone).