To which structures does the quadratus lumborum insert?

The quadratus lumborum is a deep muscle in the lower back that plays a significant role in stabilizing the pelvis and lumbar spine. Its primary insertions are on rib 12 and the transverse processes of the lumbar vertebrae L1 through L4. This anatomical connection allows the quadratus lumborum to assist in movements such as lateral flexion of the spine, as well as providing stabilization during various activities that involve the trunk.

The other choices refer to different muscles and their respective insertion points. Anterior iliac crest and pubic crest are associated with muscles like the rectus abdominis, while the xiphoid process and linea alba are related to the rectus abdominis and external oblique. Additionally, the base of the 2nd and 3rd metacarpals pertains to the hand muscles, particularly the flexor carpi radialis or other wrist flexors. Understanding the specific anatomical features of the quadratus lumborum helps emphasize its relevance in both functional movement and therapeutic applications in sports massage and physical therapy.