thoracolumbar fascia

It forms the thickened lower border of two of the layers of the thoracolumbar fascia.

Latissimus dorsi: originates at the supraspinous ligament & thoracolumbar fascia, inserts in the humerus.

The thoracolumbar fascia (lumbodorsal fascia) is a deep investing membrane which covers the deep muscles of the back of the trunk.

Erector spinae is covered in the lumbar and thoracic regions by the Thoracolumbar fascia, and in the cervical region by the nuchal ligament.

The medial branch of the superior cluneal nerve passes over the iliac crest through a tunnel formed by the thoracolumbar fascia and the superior rim of the iliac crest.

It can be thought of as the lower border of the thoracolumbar fascia and is occasionally accompanied by a smaller ligamentous band passing between the fourth lumbar vertebra and the iliac crest.

Its fibers run perpendicular to the external oblique muscle, beginning in the thoracolumbar fascia of the lower back, the anterior 2/3 of the iliac crest (upper part of hip bone) and the lateral half of the inguinal ligament.

Many large and small muscles have relationships with the ligaments of the sacroiliac joint including the piriformis (see "piriformis syndrome", a condition often related with sacroiliac joint dysfunction), biceps femoris, gluteus maximus and minimus, erector spinae, latissimus dorsi, thoracolumbar fascia, and iliacus.