The sacrum is connected to the ilium by the sacroiliac joint (articulatio sacroiliaca).

This joint is formed between the auricular articular surface of the sacrum (facies auricularis) and the auricular articular surface of the ilium (also facies auricularis).

The joint capsule is attached along the edge of the articular surfaces. It is strong, fibrous, and strengthened with numerous ligaments.

According to the classification, the joint is plane, multiaxial, simple and combined (with the same joint of the opposite side).

The joint is virtually immobile due to the equal area of the articular surfaces and the strong ligamentous apparatus.

It consists of several ligaments:

• The anterior sacroiliac ligament (ligamentum sacroiliacum anterius) passes obliquely from the pelvic surface of the sacrum to the ilium.

  

  

• The posterior sacroiliac ligament (ligamentum sacroiliacum posterius) arises from the superior and inferior posterior iliac spines and attaches to the lateral crest of the sacrum.

  

  

• The interosseous sacroiliac ligament (ligamentum sacroiliacum interosseum) is the strongest, it fuses with the posterior surface of the articular capsule, filling the gap between the sacral and iliac tuberosities.

  

• The iliolumbar ligament (ligamentum iliolumbale) arises from the transverse processes of the lumbar vertebrae

  4-5. It inserts into the crest of the ilium and its tuberosity.

  

  

  This joint has no additional structures.

  The following vessels and nerves take part in the blood supply and innervation of the joint.

• Arteries: lumbar arteries 3-4 (art. lumbales III-IV), internal iliac artery (a. iliaca interna), external iliac artery (a. iliaca externa)

• Veins: internal iliac vein (v. iliaca interna)

• Nerves: sensory fibers from the sacral plexus (plexus sacralis)

Dictionary

Sacroiliac joint

Sacroiliac joint

art. sacroiliaca

Sacrum

os sacrum

Ilium

os ilium

Auricular surface

facies auricularis

Anterior sacroiliac ligament

lig. sacroiliacum anterius

Posterior sacroiliac ligament

lig. sacroiliacum posterius

Interosseous sacroiliac ligament

lig. sacroiliacum interosseum

Iliolumbar ligament

lig. iliolumbale

Lumbar arteries 3-4

art. lumbales III-IV