The sacrotuberous ligament (great or posterior sacrosciatic ligament) is situated at the lower and back part of the pelvis. It is flat, and triangular in form; narrower in the middle than at the ends.

Structure

It runs from the

sacrum The sacrum (plural: ''sacra'' or ''sacrums''), in human anatomy, is a large, triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1S5) between ages 18 and 30. The sacrum situates at the upper, back part ...

(the lower transverse sacral tubercles, the inferior margins sacrum and the upper coccyx) to the

tuberosity of the ischium The ischial tuberosity (or tuberosity of the ischium, tuber ischiadicum), also known colloquially as the sit bones or sitz bones, or as a pair the sitting bones, is a large swelling posterior (anatomy), posteriorly on the superior ramus of the ...

. It is a remnant of part of

Biceps femoris The biceps femoris () is a muscle of the thigh located to the posterior, or back. As its name implies, it has two parts, one of which (the long head) forms part of the hamstrings muscle group. Structure It has two heads of origin: *the ''long h ...

muscle. The sacrotuberous ligament is attached by its broad base to the posterior superior iliac spine, the posterior sacroiliac ligaments (with which it is partly blended), to the lower transverse sacral tubercles and the lateral margins of the lower sacrum and upper coccyx. Its oblique fibres descend laterally, converging to form a thick, narrow band that widens again below and is attached to the medial margin of the ischial tuberosity. It then spreads along the ischial ramus as the falciform process, whose concave edge blends with the fascial sheath of the internal pudendal vessels and pudendal nerve. The lowest fibres of

gluteus maximus The gluteus maximus is the main extensor muscle of the hip. It is the largest and outermost of the three gluteal muscles and makes up a large part of the shape and appearance of each side of the hips. It is the single largest muscle in the huma ...

are attached to the posterior surface of the ligament; superficial fibres of the lower part of the ligament continue into the tendon of biceps femoris. The ligament is pierced by the coccygeal branches of the inferior gluteal artery, the perforating cutaneous nerve and filaments of the coccygeal plexus.

Variation

The membranous falciform process of the sacrotuberous ligament was found to be absent in 13% of

cadavers A cadaver or corpse is a dead human body that is used by medical students, physicians and other scientists to study anatomy, identify disease sites, determine causes of death, and provide tissue to repair a defect in a living human being. S ...

. When present it extends towards the ischioanal fossa travelling along the ischial ramus and fusing with the obturator fascia. The lower border of the ligament was found to be directly continuous with the tendon of origin of the long head of the

in approximately 50% of subjects.Vleeming, A., R. Stoeckart, et al. (1989). "The sacrotuberous ligament: a conceptual approach to its dynamic role in stabilizing the sacroiliac joint." Clinical Biomechanics 4(4): 200–203.

could therefore act to stabilise the sacroiliac joint via the sacrotuberous ligament.

Function

The sacrotuberous ligament contains the coccygeal branch of the

inferior gluteal artery The inferior gluteal artery (sciatic artery), the smaller of the two terminal branches of the anterior trunk of the internal iliac artery, is distributed chiefly to the buttock and back of the thigh. It passes down on the sacral plexus of nerve ...

Clinical significance

If the

pudendal nerve The pudendal nerve is the main nerve of the perineum. It carries sensation from the external genitalia of both sexes and the skin around the anus and perineum, as well as the motor supply to various pelvic muscles, including the male or ...

becomes entrapped between this ligament and the

sacrospinous ligament The sacrospinous ligament (small or anterior sacrosciatic ligament) is a thin, triangular ligament in the human pelvis. The base of the ligament is attached to the outer edge of the sacrum and coccyx, and the tip of the ligament attaches to th ...

causing perineal pain, the sacrotuberous ligament is surgically severed to relieve the pain.

Additional images

File:Gray319.png, Articulations of pelvis. Anterior view. File:Gray542.png, The superficial branches of the internal pudendal artery. File:Gray1077.png, The posterior aspect of the rectum exposed by removing the lower part of the sacrum and the coccyx. File:Gray1243.png , Nélaton's line and Bryant's triangle.

References

External links

* – "Deep muscles of the gluteal region with gluteus medius and maximus muscles removed." * – "Posterior view of the bones and ligaments of the hip joint." * – "The Female Perineum" * – "The Male Perineum and the Penis: Boundaries of the Ischioanal fossa" * *
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at the

Dartmouth Medical School The Geisel School of Medicine at Dartmouth is the graduate medical school of Dartmouth College in Hanover, New Hampshire. The fourth oldest medical school in the United States, it was founded in 1797 by New England physician Nathan Smith. It is ...

's Department of Anatomy {{Authority control Ligaments of the torso Ligaments