A deep muscle of the posterior abdominal wall that stabilizes the lower spine and helps bend the trunk sideways.
Structure
The muscle is roughly rectangular, attaching to the iliac crest below and to the twelfth rib and the transverse processes of the lumbar vertebrae above. It lies deep to the erector spinae.
Function
Acting on one side, it produces lateral flexion of the trunk. Acting bilaterally, it stabilizes the lumbar spine and helps fix the twelfth rib during heavy breathing.
Clinical note
Tightness in this muscle is a common contributor to chronic low-back pain.
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Quadratus Lumborum starts with Q and ends with M. Browse other body parts along the same letter.
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