Sacrum

The sacrum a bone at the end of the spine. It articulates with the hip bone at two sacroiliac joints.

It is actually formed from the fusion of five vertebrae, and sits below L5, and above the coccyx. It is concave facing fowards, thus its curvature is considered a kyphosis.

The sacrum has dorsal and ventral foramina through which nerves can pass. Inferiorly, the sacral canal opens at the sacral hiatus.