Which muscle has an origin that includes the iliac crest, iliolumbar ligament, and thoracolumbar fascia?

Which muscle has an origin that includes the iliac crest, iliolumbar ligament, and thoracolumbar fascia?

• A. Longissimus thoracis
• B. Quadratus lumborum
• C. Spinalis cervicis
• D. Latissimus dorsi

Answer: (B)

Determining where a muscle starts helps you identify it, because different muscles anchor to distinct bony and fascial attachments. The described origin—iliac crest, iliolumbar ligament, and thoracolumbar fascia—matches quadratus lumborum. This muscle sits in the posterior abdominal wall and fibers arise from the iliac crest and the iliolumbar ligament, with attachments blending into the thoracolumbar fascia. Its role includes stabilizing the lumbar spine and aiding in lateral flexion, with insertion on the lower border of the 12th rib and the transverse processes of L1–L4. The other muscles have different origin patterns: longissimus thoracis mainly originates from lumbar transverse processes and the thoracolumbar fascia but not the iliac crest or iliolumbar ligament; spinalis cervicis originates from spinous processes in the cervical region; latissimus dorsi originates from the iliac crest and thoracolumbar fascia as well, but not from the iliolumbar ligament as part of its origin.

Determining where a muscle starts helps you identify it, because different muscles anchor to distinct bony and fascial attachments. The described origin—iliac crest, iliolumbar ligament, and thoracolumbar fascia—matches quadratus lumborum. This muscle sits in the posterior abdominal wall and fibers arise from the iliac crest and the iliolumbar ligament, with attachments blending into the thoracolumbar fascia. Its role includes stabilizing the lumbar spine and aiding in lateral flexion, with insertion on the lower border of the 12th rib and the transverse processes of L1–L4.

The other muscles have different origin patterns: longissimus thoracis mainly originates from lumbar transverse processes and the thoracolumbar fascia but not the iliac crest or iliolumbar ligament; spinalis cervicis originates from spinous processes in the cervical region; latissimus dorsi originates from the iliac crest and thoracolumbar fascia as well, but not from the iliolumbar ligament as part of its origin.