Final answer:
In a posterior pelvic tilt, the tailbone moves up (superior) and the pubic bone moves down (inferior), resulting in a flattened lumbar spine. This pelvic movement affects the curvature of the lower back and involves the muscles and ligaments that are connected to the hip bones, including the iliac crest, ilia, and the sacroiliac joint ligaments.
Step-by-step explanation:
With posterior pelvic tilt, the tailbone (coccyx) moves superior and the pubic bone moves inferior. The lumbar spine is flattened as a result of this pelvic movement. The posterior pelvic tilt involves a reduction in the normal lumbar lordosis and can lead to a decrease in lower back curvature.
When considering the anatomy of the pelvic region, the iliac crest found at the top of the hips moves downwards in a posterior tilt, and the anterior superior iliac spine (ASIS) moves backwards. This movement can impact the muscles and ligaments that attach to the pelvis, particularly the strong ligaments supporting the sacroiliac joint, such as the sacrospinous and sacrotuberous ligaments. The lumbar vertebrae, ilia of the hip bones, and muscles like the psoas major and iliacus are involved in maintaining posture and stabilizing the body. Posterior pelvic tilt can alter the alignment of the pelvic bones, including the movement of the ischial tuberosity and the normative angles of the pelvic brim and pelvic outlet.