The edge of the quadratus lumborum that is most accessible is which direction?

• A. Lateral
• B. Medial
• C. Superior
• D. Inferior

Answer: (A)

The key idea here is surface anatomy—the part of the muscle that sits closest to the skin and can be felt from the outside. The quadratus lumborum runs along the posterior abdominal wall from the iliac crest up to the 12th rib and the lower spine. Its outer, lateral border sits along the flank and toward the midaxillary line, making it the most superficial edge and easiest to palpate. The medial border lies right up against the psoas and the spine, which makes it deeper and harder to access. The superior border is tucked under the 12th rib and diaphragm, and the inferior border near the iliac crest is also harder to access due to surrounding structures. So the lateral edge is the most accessible.