Muscle · Lumbar spine

Iliocostalis lumborum

Musculus iliocostalis lumborum

The pelvis-to-ribs section of the outermost erector spinae column, and the part of that column a hand actually reaches in the low back. It rises with the rest of the erector mass from the broad tendon anchored to the sacrum, the back of the iliac crest and the thoracolumbar fascia, then runs upward and outward to catch the lower six or seven ribs at their angles. Sitting furthest from the midline, it has the longest lever of the three columns for side-bending, and because its top end is ribs rather than vertebrae it works as much on the rib cage as on the spine.