👉 The term "sacroposterior" is a medical term that refers to the area of the body where the spinal cord ends and the brain begins. This location is located in the lower back, between the vertebrae (vertebraes) 2-5, and it's usually located just above the level of the level of the third lumbar vertebra. Sacroposterior is also known as sacroiliac joint or iliofemoral joint. This joint