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    Related Topics

    From Musculoskeletal System

    Metatarsals (5 bones)
    5 bones forming the mid-foot.
    Carpals (8 bones)
    8 wrist bones.
    Obliques (External and Internal)
    Muscles responsible for torso rotation.
    Anterior Longitudinal Ligament
    Spinal ligament running along the front of the vertebral column.
    Sternocleidomastoid
    Muscle that rotates and flexes the neck.
    Flexor and Extensor Groups
    Muscles responsible for flexing and extending the hand and wrist.
    Rotator Cuff Tendons
    Tendons of the rotator cuff muscles.
    Syndesmoses
    Fibrous joints where bones are connected by ligaments.
    Coracoacromial Ligament
    Ligament that connects the acromion to the coracoid process.
    Flexor Tendons
    Tendons that help flex the fingers and toes.
    Maxillae
    Upper jaw bones that house the teeth and form part of the orbit.
    Sartorius
    Longest muscle in the body responsible for hip flexion.
    Palatine Bones
    Bones forming part of the hard palate and nasal cavity.
    Saddle Joints
    e.g., thumb joint
    Abductor Digiti Minimi Muscle
    The abductor digiti minimi muscle is a hypothenar muscle that abducts and flexes the little finger, aiding grip and precision in hand movements.
    Rectus Abdominis
    Abs muscle that flexes the trunk.
    Scapula
    Shoulder blade providing attachment for muscles of the upper limb.
    Ribs (12 Pairs)
    12 pairs of bones that form the sides of the thoracic cage.
    Tibia
    Shin bone, the larger bone in the lower leg.
    Sphenoid Bone
    Bone forming part of the base of the skull and sides of the orbits.
    Fibula
    Smaller bone in the lower leg, located alongside the tibia.
    Ligamentum Flavum
    Spinal ligament connecting the laminae of adjacent vertebrae.
    Wormian Bones
    Sutural bones in the skull.
    Cranial Bones
    Bones of the skull that protect the brain.
    Ilium
    Uppermost and largest part of the hip bone.

    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? The tibia is the second largest bone in the body after the femur.