The sacrotuberous ligament is a prominent and robust ligament in the pelvis, playing a critical role in pelvic stability and load transfer. Its name provides clues to its anatomical connections: the sacrum and the ischial tuberosity.
Location
The sacrotuberous ligament is found in the posterior part of the pelvis. It spans from the lower part of the sacrum and the coccyx (the tailbone) to the ischial tuberosity of the hip bone.
Structure
Shape & Size: The ligament is broad, flat, and triangular. It starts wide at the sacrum and tapers as it reaches the ischial tuberosity.
Constitution: Composed of strong, dense fibrous connective tissue, the sacrotuberous ligament is tough and resilient.
Attachments:
- Proximal: It attaches to the posterior aspect of the sacrum, the lateral margins of the lower sacrum, and the upper coccyx.
- Distal: It narrows as it progresses inferiorly and laterally to attach to the ischial tuberosity.
Relation: The sacrotuberous ligament runs somewhat parallel to the sacrospinous ligament, though the sacrotuberous is larger and more superficial.
Function
- Pelvic Stability: The sacrotuberous ligament is a primary stabilizer of the sacroiliac joint. By providing a strong connection between the sacrum and the ischial tuberosity, it ensures the sacrum does not tilt forward excessively.
- Load Transfer: As part of the posterior pelvic ring, the sacrotuberous ligament assists in transferring upper body weight from the spine to the hip bones and lower limbs.
- Muscle Attachment: Several muscles have attachments or are related to the sacrotuberous ligament, including the gluteus maximus. This relationship aids in movements and provides additional stability.
- Limiting Pelvic Movement: The ligament restricts excessive movement of the sacrum, especially preventing its forward rotation.
Clinical Significance
The sacro-iliac (SI) joint plays a pivotal role in pelvic stability and weight transfer from the spine to the lower limbs. Clinically, dysfunction or inflammation of the SI joint, termed sacroiliitis, can manifest as lower back, hip, or buttock pain. This pain may be exacerbated during prolonged standing, climbing stairs, or even while sleeping on the affected side. SI joint pain can mimic symptoms of other conditions, like lumbar disc herniation or hip osteoarthritis, making differential diagnosis essential. Pregnancy can also impact the SI joint, as the hormone relaxin increases ligament laxity, potentially leading to SI joint pain. Inflammatory conditions, like ankylosing spondylitis, can also involve the SI joint, making it a focal point in the evaluation of back pain in younger individuals. Accurate diagnosis, often involving provocative physical tests and imaging, is crucial, as targeted treatments can significantly improve patient outcomes.
