[2][1]: 1137  It spans the length of the back, extending between the neck superiorly and the sacrum inferiorly.

[3] The thoracolumbar fascia is most prominent at its lower end[1]: 814–815  where its various layers fuse into a thick composite.

[2] In the thoracic region, the thoracolumbar fascia consists of a single layer - an upward extension of the posterior layer of the lumbar fascia, becoming progressively thinner before fading out above the 1st rib, replaced by the splenius muscle.

Superiorly, it terminates by becoming continuous with the superficial layer of deep cervical fascia of the posterior neck.

[1]: 1137  The thickened, united inferior portion attaches firmly to the posterior superior iliac spine, and the sacrotuberous ligament.