Lumbar triangles

The superior lumbar triangle (Grynfeltt) is an inverted triangle. The base is the twelfth rib, the posterior border is the erector spinae, the anterior border is the posterior margin of the internal oblique, and the apex is the iliac crest inferiorly.
The inferior triangle (Petit) is located between the external oblique, the latissimus dorsi, and the iliac crest.