Which is the insertion of the quadratus lumborum?

• A. Last rib and transverse processes of 1st-4th lumbar vertebrae
• B. Central tendon
• C. Anterior part of iliac crest
• D. Inner surfaces of lower six ribs

Answer: (A)

The main idea here is to know where the quadratus lumborum attaches at its insertion. This muscle reaches from the iliac crest up to the lower rib and the lumbar transverse processes, specifically inserting on the inferior border of the 12th rib and the transverse processes of the first through fourth lumbar vertebrae. That placement explains its role in depressing the 12th rib during forced expiration and in aiding lateral flexion of the spine. The central tendon is the insertion point for the diaphragm, not for the quadratus lumborum. The inner surfaces of the lower six ribs are also associated with the diaphragm and some intercostal muscles, not with this muscle’s insertion. The anterior part of the iliac crest is an origin site for the quadratus lumborum, not an insertion point, so it wouldn’t be the correct insertion.