The bone below the waist is the sacrum, an important part of the pelvis.
The sacrum is an inverted triangle formed by the fusion of five sacral vertebrae: the sacral spine, the sacral base, the dorsal facet, the lateral facet, and the pelvic facet. The sacrum and pelvis play a role in protecting the pelvic organs such as the uterine adnexa, bladder, rectum, etc. and in conducting gravity, and there are soft tissues such as muscles, tendons, fascia, ligaments, etc. attached to the sacral area.
There is a significant difference between the male and female sacrum, with the male sacrum being long and narrow and the female sacrum being short and wide, in order to help women adapt to childbearing and labor. Sacral pain is most often caused by sports injuries and degenerative conditions, such as herniated discs and muscle soft tissue injuries.
If you experience sacral pain and discomfort, it is recommended that you seek medical diagnosis and treatment in a timely manner.