What joint connects the lower spine to the pelvis?

The sacro-iliac joint is the correct answer because it specifically serves as the connection point between the lower spine and the pelvis. This joint is located where the sacrum, which is the triangular bone at the base of the spine, meets the ilium, which is part of the hip bone. The sacro-iliac joint plays a crucial role in providing stability to the pelvis and transferring weight between the upper body and the legs during movement.

Understanding the significance of the sacro-iliac joint is essential, as it allows for limited movement which helps absorb shock during walking, running, and other activities. The joint's stability is important in various physical activities and impacts overall mobility and balance.

Other options refer to different joints that do not fulfill the role of connecting the lower spine to the pelvis. For instance, the symphysis pubis is located at the front of the pelvis and connects the two pubic bones but does not link the spine to the pelvis. The temporomandibular joint is involved in jaw movement, making it unrelated to spinal and pelvic connections, while the lumbar joint refers to the intervertebral joints in the lumbar region of the spine rather than the connection to the pelvis.