Origin: Which muscle originates from the iliac crest and thoracolumbar fascia?

Origin: Which muscle originates from the iliac crest and thoracolumbar fascia?

• A. Iliocostalis lumborum
• B. Longissimus capitis
• C. Splenius cervicis
• D. Spinalis thoracis

Answer: (A)

This question hinges on where the muscle starts (its origin) along the back. The iliocostalis lumborum is the muscle that originates from the iliac crest and the thoracolumbar fascia, making it the clear match for a lower back origin that spans the pelvis up the lumbar region. This muscle sits as the lateral column of the erector spinae, and from that origin it runs upward to the lower ribs, helping to extend the spine and bend it laterally. In contrast, longissimus capitis starts higher up—from transverse processes and goes to the skull—so it doesn’t originate from the iliac crest or thoracolumbar fascia. Splenius cervicis comes from the spinous processes of the upper thoracic spine and the nuchal ligament, not from the iliac crest. Spinalis thoracis originates from more inferior thoracic spinous processes and doesn’t attach to the iliac crest or thoracolumbar fascia. So the muscle with that distinctive pelvic-to-lumbar origin is the iliocostalis lumborum.

This question hinges on where the muscle starts (its origin) along the back. The iliocostalis lumborum is the muscle that originates from the iliac crest and the thoracolumbar fascia, making it the clear match for a lower back origin that spans the pelvis up the lumbar region. This muscle sits as the lateral column of the erector spinae, and from that origin it runs upward to the lower ribs, helping to extend the spine and bend it laterally. In contrast, longissimus capitis starts higher up—from transverse processes and goes to the skull—so it doesn’t originate from the iliac crest or thoracolumbar fascia. Splenius cervicis comes from the spinous processes of the upper thoracic spine and the nuchal ligament, not from the iliac crest. Spinalis thoracis originates from more inferior thoracic spinous processes and doesn’t attach to the iliac crest or thoracolumbar fascia. So the muscle with that distinctive pelvic-to-lumbar origin is the iliocostalis lumborum.