The bones in the buttocks are called the pelvis. The pelvis consists of the iliac wings, which are at the top of the pelvis on both sides, and below the iliac wings are the pubic bone and the sciatic bone, and the sciatic bone is outwardly located in the acetabulum, which is the main component of the hip joint. In addition, there is the femoral head on the outside of the acetabulum, which together with the acetabulum constitutes the femoral head of the hip joint; further down are the femoral neck, the femoral trochanter and the femoral stem; and there is the sacrum on the back side of the pelvis, which together with the iliac bone constitutes the sacroiliac joint, which is the most important structure for the maintenance of stability of the lumbosacral region. Inflammation of the sacroiliac joints usually occurs due to frequent irritation, cold, strain, and autoimmune diseases, resulting in pain and unfavorable movement of this area.