Espiral AtlasSacroiliac joint
articulatio sacroiliaca
Study entry
Classification
Complex, strong and weight-bearing: an anterior synovial joint (between the auricular surfaces of the sacrum and the ilium, covered with cartilage) and a posterior syndesmosis (between the tuberosities of the same bones).
Surfaces
Auricular surfaces of the sacrum and the ilium, with irregular but congruent elevations and depressions that interlock.
Capsule
The thin anterior sacroiliac ligaments form the anterior part of the capsule. The numerous interosseous ligaments (about 10 cm²) are the main structures in the transfer of weight from the axial skeleton to the ilia. The posterior ones continue the same mass of fibrous tissue; their oblique fibers make the axial weight pull the ilia medially, compressing the sacrum. The iliolumbar ligaments help. Inferiorly the posterior ones receive fibers from the ilium and the coccyx and form the sacrotuberous ligament, from the ilium and sacrum to the ischial tuberosity; the sacrospinous runs from the sacrum and coccyx to the ischial spine, and the two turn the sciatic notch into the greater and lesser sciatic foramina.
Movements
Slight gliding and rotation movements, limited by the interlocking of the bones and by the ligaments. The weight is transmitted anterior to the axis of the joints and tends to push the upper part of the sacrum downward and forward; the sacrotuberous and sacrospinous ligaments resist this rotation.
Blood supply
[CHECK: Moore does not describe it in the passages consulted (look in another source).]
Innervation
[CHECK: Moore does not describe it in the passages consulted (look in another source).]
Source: cap. 6, «Articulaciones sacroilíacas»