Lower limb
Sacroiliac and iliolumbar ligament complex
Ligamenta sacroiliaca (anteriora, posteriora, interossea & iliolumbale)
- Origin
- Sacral tuberosity, auricular surface of sacrum, and transverse process of L5 (iliolumbar ligament)
- Insertion
- Iliac tuberosity, posterior superior iliac spine (PSIS), and iliac crest
- Function
- Strongest ligament complex in the human body; ensures form and force closure of the sacroiliac joint, transferring axial spine load to the pelvis and lower limbs
- Innervation
- Dorsal rami of L4–S3 spinal nerves
- Movement & chain
- Permits 2°–4° of micro-motion (nutation and counternutation)
- Palpation
- Palpable deeply medial and inferior to PSIS
- Clinical
- Sacroiliitis in spondyloarthropathies (ankylosing spondylitis / HLA-B27); pregnancy-related pelvic girdle pain (relaxin-induced hypermobility); SI joint dysfunction.
- Segmental innervation
- L4–S3
- In clinical practice
- Laslett provocation test cluster (FABER, Thigh thrust, Compression, Distraction), pelvic stabilization belt, and deep core rehabilitation
- Region in the model
- Lower limb