The iliolumbar ligament passes through the transverse process in the fifth lumbar vertebra down to the iliac crest's inner lip on the posterior side. It forms a thickened lower border for two thoracolumbar fascia layers. The ilium is the largest segment of the coaxial bone. There are six ligaments in the lumbar spine region. Assisted by the lateral lumbosacral ligament, the iliolumbar ligament strengthens the lumbosacral joint. Supraspinous, interspinous, ligament flava, anterior longitudinal, and posterior longitudinal ligaments also play a role in strengthening vertebral joints. This ligament stabilizes the connection between the pelvis and lower back, limiting trunk side-flexion. When this ligament becomes injured, bending to one side becomes painful in the sacroiliac joint area, though injuries to this ligament are rare. The iliolumbar ligament, which has five bands, is one of three vertebra-pelvic ligaments responsible for stabilizing the lumbrosacral spine in the pelvis, along with the sacrospinous and sacrotuberous ligaments. The function of this ligament is essential to restraining movement of the lumbrosacral junction.
Written and medically reviewed by the Healthline Editorial Team
In Depth: Iliolumbar ligament