Pubic Bone: Ligament Attachments, Functions, and Clinical Relevance

What ligaments are attached to the pubic bone?

The pubic bone, a crucial component of the pelvic girdle, serves as an attachment point for several key ligaments that provide stability, support, and facilitate the functional integrity of the pelvis and surrounding structures. These ligaments are primarily concentrated around the pubic symphysis, the cartilaginous joint connecting the two pubic bones, and also include structures that contribute to the pelvic floor and abdominal wall.

Understanding the Pubic Bone and Pelvic Girdle

The pubic bone forms the anterior portion of the hip bone (os coxae), uniting with its contralateral counterpart at the pubic symphysis. Together with the ilium and ischium, it creates the bony ring of the pelvis, which bears the weight of the upper body, transmits forces to the lower limbs, and provides attachment for numerous muscles and ligaments essential for posture, movement, and organ support. The robust network of ligaments connecting to and around the pubic bone is vital for maintaining the structural stability of this complex region.

Ligaments of the Pubic Symphysis

The pubic symphysis is a secondary cartilaginous joint (symphysis) where the two pubic bones meet. It is reinforced by several strong ligaments that limit movement and provide significant stability.

• Superior Pubic Ligament:

  • Location: Runs along the superior aspect of the pubic symphysis, connecting the pubic crests of both pubic bones.
  • Function: Limits superior separation of the pubic bones and helps reinforce the joint from above.

• Inferior Pubic Ligament (Arcuate Pubic Ligament):

  • Location: Forms a strong, thick arch along the inferior border of the pubic symphysis, connecting the inferior rami of the pubic bones.
  • Function: Provides significant structural support from below, preventing inferior separation and contributing to the stability of the pubic arch. It forms the superior boundary of the subpubic angle.

• Anterior Pubic Ligament:

  • Location: A strong, interwoven network of fibers covering the anterior surface of the pubic symphysis. It blends with the aponeuroses of the external oblique muscles and fibers from the rectus abdominis.
  • Function: Reinforces the joint anteriorly, resisting anterior-posterior shearing forces and limiting excessive movement.

• Posterior Pubic Ligament:

  • Location: A less distinct and thinner layer of fibers on the posterior aspect of the pubic symphysis.
  • Function: Provides some posterior reinforcement, though it is not as robust as the anterior ligament.

Other Ligaments Associated with the Pubic Bone

Beyond the immediate vicinity of the pubic symphysis, several other important ligaments attach to or are closely associated with the pubic bone, contributing to pelvic and abdominal wall integrity.

• Inguinal Ligament (Poupart's Ligament):

  • Location: Extends from the anterior superior iliac spine (ASIS) of the ilium to the pubic tubercle of the pubic bone.
  • Function: Forms the inferior border of the anterior abdominal wall, creating a critical passage (inguinal canal) for structures passing between the abdominal cavity and the thigh. It is a thickened inferior border of the aponeurosis of the external oblique muscle.

• Lacunar Ligament (Gimbernat's Ligament):

  • Location: A crescent-shaped expansion of the medial end of the inguinal ligament, attaching to the pectineal line of the pubic bone.
  • Function: Forms the medial boundary of the femoral ring, an opening through which the femoral artery, vein, and nerve pass.

• Pectineal Ligament (Cooper's Ligament):

  • Location: A strong, fibrous band that runs along the pectineal line of the pubic bone, continuous with the lacunar ligament.
  • Function: Provides additional reinforcement to the superior pubic ramus and serves as an important landmark and attachment point for various structures, including the conjoint tendon and the posterior wall of the inguinal canal.

• Perineal Membrane (Inferior Fascia of the Urogenital Diaphragm):

  • Location: A dense, fibrous sheet spanning the anterior portion of the pelvic outlet, attaching laterally to the inferior rami of the pubic and ischial bones. The deep transverse perineal ligament is a thickened posterior border of this membrane.
  • Function: Supports the structures of the urogenital triangle, provides attachment for the external urethral sphincter and deep transverse perineal muscles, and helps maintain continence.

Functional Significance in Movement and Stability

These ligaments are integral to the biomechanics of the pelvis:

• Pelvic Stability: They collectively resist forces that could otherwise lead to separation or excessive movement at the pubic symphysis, especially during weight-bearing activities, gait, and childbirth.
• Force Transmission: By stabilizing the pubic symphysis, they ensure efficient transfer of forces between the trunk and lower limbs, crucial for athletic performance and daily activities.
• Core and Pelvic Floor Support: Ligaments like the inguinal and perineal membrane contribute to the structural integrity of the abdominal and pelvic floor regions, supporting abdominal organs and maintaining continence.

Clinical Relevance and Injury

Injury or dysfunction of these ligaments can lead to significant pain and functional limitations. Conditions such as pubic symphysis dysfunction (PSD), often experienced during pregnancy due to hormonal changes that loosen ligaments, or direct trauma, can compromise the stability of the pubic joint. Understanding the precise anatomical attachments and functions of these ligaments is crucial for diagnosing and managing such conditions, as well as for designing effective rehabilitation strategies.

Conclusion

The pubic bone, while seemingly a small part of the pelvis, is a critical nexus for a complex network of ligaments. The superior, inferior (arcuate), anterior, and posterior pubic ligaments directly stabilize the pubic symphysis. Additionally, the inguinal, lacunar, pectineal, and perineal membrane ligaments attach to or are intimately associated with the pubic bone, providing broader support to the pelvic girdle, abdominal wall, and pelvic floor. These structures are indispensable for maintaining pelvic integrity, facilitating efficient movement, and ensuring overall musculoskeletal health.