Quadratus Lumborum - Podcast Version 0:00 / 0:00 1x 0.25x 0.5x 0.75x 1x 1.25x 1.5x 1.75x 2x The quadratus lumborum is a muscle of the posterior abdominal wall. It is a thick muscular sheet, quadrilateral in shape, and positioned superficial to the psoas major. Attachments: Originates from the iliac crest and iliolumbar ligament. The fibres travel superomedially, inserting onto the transverse processes of L1 – L4 and the inferior border of the 12th rib. Actions: Extension and lateral flexion of the vertebral column. It also fixes the 12th rib during inspiration, so that the contraction of diaphragm is more efficient. Innervation: Anterior rami of T12 – L4 nerves. Blood supply: Lumbar, median sacral, iliolumbar and subcostal arteries. By TeachMeSeries Ltd (2026) Fig 1The quadratus lumborum of the posterior abdominal wall. Pro Feature - 3D Model You've Discovered a Pro Feature Access our 3D Model Library Explore, cut, dissect, annotate and manipulate our 3D models to visualise anatomy in a dynamic, interactive way. Learn More Frequent questions What is the quadratus lumborum muscle? The quadratus lumborum is a thick, quadrilateral muscle located in the posterior abdominal wall, lying superficial to the psoas major muscle. It plays a vital role in stabilising the spine and assisting with movements of the vertebral column. What are the attachments of the quadratus lumborum? This muscle originates from the iliac crest and the iliolumbar ligament, with its fibres running superomedially to insert on the transverse processes of the lumbar vertebrae L1 to L4 and the inferior border of the 12th rib. What actions does the quadratus lumborum perform? The quadratus lumborum is responsible for extending and laterally flexing the vertebral column. Additionally, it stabilises the 12th rib during inspiration, enhancing the efficiency of diaphragm contraction. Which nerves innervate the quadratus lumborum? The quadratus lumborum is innervated by the anterior rami of the T12 to L4 spinal nerves. This innervation is crucial for its motor function and coordination during movement. What is the blood supply to the quadratus lumborum? The blood supply to the quadratus lumborum comes from several arteries, including the lumbar arteries, median sacral artery, iliolumbar artery, and subcostal artery. This vascularisation supports the muscle's metabolic and functional demands. Rate This Article