The Quadratus Lumborum, lumbo pelvic instability and stretching IMAGE A
QUADRATUS LUMBORUM (QL) The quadrilateral quadratus lumborum forms a thick quadrilateral muscular sheet in the posterior abdominal wall. It spans the last rib, iliac crest and spine, and has a free lateral border. See images A & B. Uncommonly known, Kapandji (Physiology of the Joints page 106, and image below) tells us that the QL more complex and is in fact comprised of 3 sets of fibers, see image C on next page: 1. Fibers running directly between the last rib and the iliac crest (orange arrows) 2. Fibers running between the last rib and the transverse processes of the five lumbar vertebrae (red arrows)
Image A. Anterior QL IMAGE B
3. Fibers running between the transverse processes of the first four lumbar vertebrae and the iliac crest (green arrows). These fibers are continuous with the transversospinalis (violet arrows) which lie in the spaces between the transverse processes. The 3 sets of fibers are also arranged in 3 planes-the posterior plane consisting of the straight intercostal fibers, the intermediate plane of the intervertebral fibers, and the anterior plane of the costovertebral fibers.
Image B. Posterior QL