Where is the S1 vertebrae?

The S1 vertebra, or first sacral vertebra, is located at the base of the spine, forming the uppermost part of the sacrum. It connects to the last lumbar vertebra (L5) above it and articulates with the ilium bones of the pelvis on either side. The S1 vertebra plays a crucial role in supporting the weight of the upper body and facilitating movement between the spine and pelvis.