The pelvis, a robust bony structure, relies on a complex network of ligaments to maintain stability, facilitate movement, and support the body’s weight during daily activities. Key ligaments such as the posterior sacroiliac ligament, sacrospinous ligament, and sacrotuberous ligament play critical roles in reinforcing the sacroiliac joint and forming the greater and lesser sciatic foramina, which are essential for neurovascular passage. This article provides an in-depth exploration of the ligaments of the pelvis, their anatomical features, and their significance in human biomechanics.
Labeled Parts of the Pelvic Ligaments: Detailed Explanations
Sacrum
The sacrum is a triangular bone at the base of the spine, formed by the fusion of five sacral vertebrae, which articulates with the ilium at the sacroiliac joint. It serves as the anchor point for several pelvic ligaments, transmitting the weight of the upper body to the pelvis and lower limbs.
Posterior Superior Iliac Spine
Located on the posterior aspect of the ilium, the posterior superior iliac spine is a bony landmark where the posterior sacroiliac ligament attaches. This projection helps stabilize the sacroiliac joint and is often used as a reference point in clinical assessments of the pelvis.
Recommended Study Resource
Gray's Anatomy: The Anatomical Basis of Clinical Practice
Enhance your anatomical knowledge with Gray's Anatomy: The Anatomical Basis of Clinical Practice. This authoritative text offers in-depth insights and illustrations, perfect for medical students and practitioners aiming for clinical excellence.
At AnatomyNote.com, we offer free resources on anatomy, pathology, and pediatric medicine for medical students and professionals. Purchasing through our Amazon links, like Gray's Anatomy, supports our server costs and content creation at no additional cost to you.
Disclosure: As an Amazon Associate, we earn a commission from qualifying purchases.
Disclosure: As an Amazon Associate, we earn a commission from qualifying purchases at no extra cost to you.
Ilium
The ilium forms the broad, superior portion of the hip bone, providing a large surface for ligament and muscle attachments. It articulates with the sacrum via the sacroiliac joint, where ligaments like the posterior sacroiliac ligament ensure stability during weight-bearing activities.
Posterior Sacroiliac Ligament
The posterior sacroiliac ligament is a strong, fibrous band that connects the posterior surface of the sacrum to the ilium, reinforcing the sacroiliac joint. It plays a crucial role in limiting excessive movement at the joint, ensuring stability during activities like walking or lifting.
Sacrum
The sacrum, as previously noted, is central to pelvic stability, serving as the origin for ligaments like the sacrospinous and sacrotuberous ligaments. Its roughened surface provides a secure attachment for these ligaments, which help define the boundaries of the sciatic foramina.
Sacropinous Ligament
The sacrospinous ligament spans from the lateral edge of the sacrum to the ischial spine, forming the inferior boundary of the greater sciatic foramen and the superior boundary of the lesser sciatic foramen. This ligament helps stabilize the pelvis and prevents excessive rotation of the sacrum relative to the hip bones.
Anatomy Flash Cards
Master anatomy with detailed, exam-ready flash cards.
AnatomyNote.com offers free anatomy and pathology resources. Your purchase of Anatomy Flash Cards supports our site at no extra cost.
As an Amazon Associate, we earn from qualifying purchases.
Ischial Spine
The ischial spine is a sharp, bony projection on the ischium where the sacrospinous ligament attaches, marking the boundary between the greater and lesser sciatic foramina. It is a critical landmark in obstetrics, as its position influences the pelvic outlet’s diameter during childbirth.
Pubis
The pubis forms the anterior portion of the hip bone, connecting with the opposite pubis at the pubic symphysis, a joint stabilized by ligaments like the subpubic ligament. It contributes to the structural integrity of the pelvis and supports the attachment of pelvic floor muscles.
Ischium
The ischium is the posteroinferior part of the hip bone, housing the ischial tuberosity and spine, which serve as attachment points for ligaments like the sacrotuberous ligament. It plays a key role in supporting the body’s weight when sitting and stabilizing the pelvis.
Ischial Tuberosity
The ischial tuberosity, a thickened area on the ischium, is the attachment site for the sacrotuberous ligament and is often called the “sitting bone” due to its role in weight-bearing when seated. It also serves as the origin for the hamstring muscles, aiding in hip extension.
Obturator Foramen
The obturator foramen is a large, oval opening formed by the ischium and pubis, which is mostly covered by a membrane in life but allows the passage of the obturator nerve and vessels. It is bordered by the ischiopubic ramus, which is stabilized by nearby ligaments.
Subpubic Angle
The subpubic angle is the angle formed by the inferior rami of the pubis at the pubic symphysis, typically wider in females to accommodate childbirth. It is reinforced by ligaments like the arcuate pubic ligament, which helps maintain the integrity of the pubic symphysis.
Ischiopubic Ramus
The ischiopubic ramus is the fused structure of the inferior ramus of the pubis and the ischial ramus, forming the lower boundary of the obturator foramen. It provides structural support to the pelvis and attachment for pelvic floor muscles and ligaments.
Greater Sciatic Foramen
The greater sciatic foramen is a large opening bounded by the greater sciatic notch, the sacrospinous ligament, and the sacrotuberous ligament, allowing the passage of the sciatic nerve, piriformis muscle, and other neurovascular structures to the lower limb. It is a critical pathway for structures exiting the pelvis to the gluteal region.
Sacrospinous Ligament
The sacrospinous ligament, as mentioned earlier, connects the sacrum to the ischial spine, contributing to the formation of the greater and lesser sciatic foramina. It also helps stabilize the pelvis by preventing excessive downward tilting of the sacrum during weight-bearing activities.
Lesser Sciatic Foramen
The lesser sciatic foramen is a smaller opening inferior to the greater sciatic foramen, bounded by the sacrospinous ligament, sacrotuberous ligament, and the ischial spine. It allows the passage of the obturator internus muscle, its nerve, and vessels from the pelvis to the gluteal region.
Sacrotuberous Ligament
The sacrotuberous ligament extends from the sacrum to the ischial tuberosity, forming the posterior boundary of the greater and lesser sciatic foramina. It provides stability to the sacroiliac joint and prevents excessive upward tilting of the sacrum during activities like running or jumping.
Physical Structure of Pelvic Ligaments
The ligaments of the pelvis are dense, fibrous bands designed to withstand significant mechanical stress while maintaining the structural integrity of the pelvis. This section examines their physical characteristics and their role in supporting the pelvic framework.
- The posterior sacroiliac ligament consists of short, strong fibers that tightly bind the sacrum to the ilium, ensuring minimal movement at the sacroiliac joint during weight-bearing activities.
- The sacrospinous ligament is a thin, triangular band that forms a critical boundary between the greater and lesser sciatic foramina, allowing the passage of neurovascular structures while stabilizing the pelvis.
- The sacrotuberous ligament is a broad, flat band that reinforces the connection between the sacrum and ischium, playing a key role in preventing rotational instability of the pelvis.
- Ligaments like the arcuate pubic ligament at the subpubic angle provide additional support to the pubic symphysis, allowing slight flexibility during movements like walking or childbirth.
- The collagenous composition of these ligaments ensures they are both strong and slightly elastic, enabling them to absorb shock and distribute forces across the pelvis during dynamic activities.
Functional Role of Pelvic Ligaments in the Human Body
Pelvic ligaments are essential for maintaining stability, facilitating movement, and protecting vital structures within the pelvis. This section explores their biomechanical and physiological contributions.
- They stabilize the sacroiliac joint, allowing it to transfer the weight of the upper body to the lower limbs during standing, walking, and running.
- The sacrospinous and sacrotuberous ligaments define the greater and lesser sciatic foramina, ensuring safe passage of the sciatic nerve and other structures without compression.
- These ligaments prevent excessive movement of the sacrum relative to the hip bones, maintaining pelvic alignment and protecting the spine’s curvature.
- They provide attachment points for muscles like the piriformis and obturator internus, which are involved in hip rotation and stabilization during locomotion.
- The subpubic angle, reinforced by ligaments, contributes to the structural framework of the pelvis, influencing its capacity to support internal organs and withstand mechanical stress.
Clinical Significance of Pelvic Ligaments
The ligaments of the pelvis are critical in clinical contexts, as their dysfunction or injury can lead to significant health issues. This section highlights their relevance in medical practice.
- Injury to the posterior sacroiliac ligament, often due to trauma or repetitive stress, can lead to sacroiliac joint dysfunction, causing lower back pain and impaired mobility.
- The sacrospinous and sacrotuberous ligaments are key landmarks in pelvic surgeries, such as those addressing pudendal nerve entrapment, where they guide surgeons to the sciatic foramina.
- During childbirth, the subpubic angle and associated ligaments may stretch, and in cases of pubic symphysis diastasis, these ligaments may fail to provide adequate support, leading to postpartum pelvic pain.
- Inflammation of the sacroiliac joint, known as sacroiliitis, often involves the posterior sacroiliac ligament, resulting in stiffness and pain that can radiate to the buttocks or thighs.
- The ligaments’ blood supply, derived from nearby arteries like the superior gluteal artery, supports their metabolic needs, but poor circulation can lead to delayed healing after injury.
In conclusion, the ligaments of the pelvis are indispensable for maintaining the structural and functional integrity of this critical region of the human body. Their intricate network, from the stabilizing posterior sacroiliac ligament to the boundary-forming sacrospinous and sacrotuberous ligaments, ensures the pelvis can support the body’s weight, facilitate movement, and protect vital structures, making them a focal point for anatomical study and clinical intervention.
