Quadratus lumborum, commonly known as back muscle is a posterior abdominal wall muscle. The shape of the muscle is irregular as well as quadrilateral and broader below than above and is the the deepest abdominal muscle.
<u>The muscle originates by the aponeurotic fibers into iliolumbar ligament and internal lip of iliac crest for about 5 centimeters . It then inserts from the lower border of last rib (rib 12) for about the half of it's length and also by the four small tendons from apices of transverse processes of upper four lumbar vertebrae. (L1-L4).</u>
