Lower limb

Sacrotuberous and sacrospinous ligaments

Ligamentum sacrotuberale et ligamentum sacrospinale

Origin

Posterior border of sacrum, coccyx, and PSIS/PIIS

Insertion

Ischial tuberosity (sacrotuberous) and ischial spine (sacrospinous)

Function

Converts greater and lesser sciatic notches into foramina; resists sacral nutation under spinal weight; continuous with biceps femoris tendon

Innervation

Branches of sacral plexus and pudendal nerve (S1–S4)

Movement & chain

Resists backward tilting of lower sacrum during weight-bearing

Palpation

Sacrotuberous ligament palpable deep in gluteal fold above ischial tuberosity

Clinical

Pudendal nerve entrapment (Alcock canal syndrome causing perineal neuropathic pain in cyclists); force transmission from hamstrings to thoracolumbar fascia.

Segmental innervation

S1–S4

In clinical practice

Pudendal nerve decompression techniques, saddle pressure relief, and hamstring chain release

Region in the model

Lower limb