Muscle Anatomy


The quadratus lumborum muscle is located in the posterior abdominal wall and lumbar region. It is a deep, flat muscle forming part of the posterior abdominal wall and contributes to the lower back's musculature.

Originating from the iliolumbar ligament and the posterior iliac crest, the quadratus lumborum takes its starting point from the bony and ligamentous structures in the lower back.

The muscle inserts into the transverse processes of the upper lumbar vertebrae (L1-L4) and the 12th rib. This insertion site establishes a connection with the vertebral column and the ribcage.

Functionally, the quadratus lumborum is involved in several actions, including lateral flexion of the spine, extension of the lumbar spine, and stabilization of the 12th rib during respiration. Additionally, it plays a role in maintaining an upright posture. The muscle is particularly active during activities that involve bending to the side, such as reaching for an object or leaning away from the midline. The quadratus lumborum contributes to the complex movements and stability of the lower back and trunk.