The hip is the joint of the waist and legs, and the skeleton is the pelvis composed of two hip bones and sacrum, with gluteus maximus, gluteus medius, gluteus minimus and piriformis attached. Hip shape backward, with iliac crest on the upper edge and gluteal groove on the lower edge. When standing upright, the buttocks are square, and the buttocks on both sides are obvious.
Female buttocks are plump and obese, and the intersection angle of posterior superior iliac crest is 90; Male hips are small, square, angular and obvious. The intersection angle between the posterior superior iliac crest is 60. The tightness of hip muscles affects the perception of hip position, but does not change the height of hip line.
The gluteal line, anatomically called gluteal sulcus or gluteal-femoral sulcus, refers to the skin sulcus between the gluteal muscle protuberance and the upper end of the posterior thigh. When standing, it is more obvious that some people's hip muscles are tight, and some muscles are slack and drooping, which affects the perception of "breech position" because of different muscle shapes, but the hip muscle shape does not change the height of breech line.
There is no significant difference between men from small to large, which is relatively stable and easy to predict. As women enter puberty, the index of (ilium width/shoulder width) × 100 gradually increases from the age of 12, and it can only be stabilized after 16. During the four years from 12 to 16, the index rose by 6.8% on average. After 12 years old, the pelvis obviously grows sideways, and the shoulders of women are narrower than those of men, so the female (ilium width/shoulder width) × 100 index is higher than that of men.