Logo

    Related Topics

    From Musculoskeletal System

    Posterior Longitudinal Ligament
    Spinal ligament running along the back of the vertebral column.
    Metacarpals (5 bones)
    5 bones forming the palm of the hand.
    Coccyx
    Tailbone, the remnant of the tail in humans.
    Thoracic Vertebrae (T1 - T12)
    Vertebrae in the upper and mid-back (T1-T12).
    Ulna
    Forearm bone on the pinky side.
    Gomphoses
    Fibrous joints where a peg fits into a socket (e.g., teeth in jaw).
    Temporal Bones
    Bones forming the lower sides of the skull and housing the ears.
    Ligamentum Flavum
    Spinal ligament connecting the laminae of adjacent vertebrae.
    Gluteus Maximus
    Largest muscle in the buttocks responsible for hip extension.
    Gastrocnemius
    Calf muscle responsible for plantarflexion of the foot.
    Masseter
    Muscle that elevates the mandible.
    Pelvic Floor Muscles
    Muscles that support pelvic organs.
    Patellar Tendon
    Tendon connecting the patella to the tibia.
    Coracoacromial Ligament
    Ligament that connects the acromion to the coracoid process.
    Posterior Cruciate Ligament (PCL)
    Knee ligament that stabilizes the joint.
    Interspinous Ligament
    Spinal ligament between adjacent vertebral spinous processes.
    Pubis
    Part of the pelvis that joins with the opposite side to form the pubic symphysis.
    Adductors
    Muscles that bring the thighs toward the midline.
    Medial Collateral Ligament (MCL)
    Knee ligament that stabilizes the inner knee.
    Achilles Tendon
    Tendon connecting the calf muscle to the heel bone.
    Nasal Bones
    Bones forming the bridge of the nose.
    Mandible
    Lower jawbone that houses the teeth.
    Rectus Abdominis
    Abs muscle that flexes the trunk.
    Humerus
    Upper arm bone connecting the shoulder to the elbow.
    Sphenoid Bone
    Bone forming part of the base of the skull and sides of the orbits.

    Sacroiliac Ligaments

    Reviewed by our medical team

    Ligaments connecting the sacrum to the iliac bones.

    1. Overview

    The sacroiliac (SI) ligaments are a group of strong, fibrous structures that stabilize the sacroiliac joints—the articulations between the sacrum and the ilium of the pelvis. These ligaments are essential for maintaining pelvic integrity, distributing weight from the upper body to the lower limbs, and limiting excessive motion at the SI joint, which is mostly an immobile or slightly mobile joint.

    2. Location

    The sacroiliac ligaments are located in the posterior pelvis, surrounding the sacroiliac joints:

    • Connect: The sacrum (S1–S4 vertebrae) to the ilium of each hip bone.

    • Span: From the lateral sacral surface to the ilial auricular surface and iliac tuberosity.

    • Lie posterior to: The sacroiliac joint capsule and anterior pelvic organs.

    3. Structure

    There are several distinct sacroiliac ligaments, classified into anterior, interosseous, and posterior groups:

    • Anterior sacroiliac ligament:

      • A thin, broad band located on the anterior surface of the joint capsule.

      • Connects the anterior sacral ala to the ilium's auricular surface.

    • Interosseous sacroiliac ligament:

      • The strongest and deepest of the SI ligaments.

      • Occupies the space between the sacrum and the ilium posterior to the joint.

      • Provides the primary stabilization of the SI joint.

    • Posterior sacroiliac ligament:

      • Located on the dorsal surface of the sacrum and ilium.

      • Subdivided into short (horizontal) and long (oblique) portions.

      • Attaches from the sacral tubercles to the posterior superior iliac spine (PSIS) and iliac crest.

    These ligaments are composed of densely packed collagen fibers capable of resisting high tensile loads and shear forces.

    4. Function

    The sacroiliac ligaments provide essential structural and mechanical functions:

    • Stabilize the sacroiliac joint: Limit anterior and inferior movement of the sacrum relative to the ilium.

    • Distribute mechanical load: Transfer weight from the spine to the pelvic girdle and lower limbs.

    • Resist shear forces: Prevent displacement during twisting, lifting, or shifting motions.

    • Anchor pelvic structures: Support the connection between the axial and appendicular skeletons.

    5. Physiological role(s)

    Though passive in nature, sacroiliac ligaments contribute to:

    • Postural integrity: Maintain pelvic alignment during upright stance, walking, and load-bearing.

    • Shock absorption: Act as tension-bearing structures during spine and hip motion.

    • Pelvic movement regulation: Control minute joint glides (nutation and counternutation) needed for locomotion and childbirth.

    • Proprioception: Contain mechanoreceptors that help the nervous system regulate posture and movement.

    6. Clinical Significance

    Dysfunction or injury to the sacroiliac ligaments can lead to pain and mobility issues:

    • Sacroiliac joint dysfunction:

      • May result from ligamentous laxity, trauma, leg-length discrepancy, or poor biomechanics.

      • Presents as lower back or buttock pain, sometimes radiating to the thigh.

    • Sacroiliitis:

      • Inflammation of the SI joint, often involving the ligaments; associated with conditions like ankylosing spondylitis and other spondyloarthropathies.

    • Ligament strain or tear:

      • Can occur from sudden rotational forces, lifting injuries, or falls.

      • May cause acute localized pain, swelling, and tenderness over the SI joint.

    • Pregnancy-related pelvic pain:

      • Hormonal relaxation of the sacroiliac ligaments increases joint mobility, which can result in pain and instability.

    • Injection or surgical intervention:

      • SI joint injections target inflammation involving these ligaments.

      • Fusion surgery may be considered for chronic, treatment-resistant SI joint instability.

    Did you know? Bone marrow is the site where red blood cells are made.