An accessory gluteus maximus muscle.

The gluteus maximus muscle is the largest, heaviest and most coarsely fibred muscle in the body which provides a thick quadrilateral pad over the ischial tuberosity. Structural changes in this muscle are critical to the evolutionary advance toward an upright stance during walking. Although its bilaminar nature' and its deep and superficial segmentation2) are a part of our current knowledge, variations of the gluteus maximus muscle are not mentioned frequently in anatomy textbooks. These variations may have a clinical significance when the surgery of this region is under consideration.