The vertebral column is made up of thirty-three individual vertebra — they are grouped into seven cervical (neck), twelve thoracic (upper back), five lumbar (low back), and five sacral (fused to form part of the pelvis) and four coccygeal bones (also fused, form the tailbone). The column is flexible to aid mobility. It provides bony protection to the delicate spinal cord.

Ankylosing spondylitis (AS) is a form of arthritis that primarily affects the spine, although other joints can become involved. There is chronic inflammation of the spinal joints that over time (but not in all cases) results in new bone formation around the affected joints, causing the spine to fuse. This can create a forward-stooped posture. The condition is prevalent predominantly in young males.