The spine, or backbone, is made of 33 individual bones called vertebrae. It provides the main support for the body, allowing the person to stand upright, bend, and twist, while protecting the spinal cord from injury. A healthy spine provides strength, is flexible, and allows movement in several directions. Strong bones and muscles, flexible tendons and ligaments, and sensitive nerves contribute to the overall health of the spine. Any of these structures affected by strain, injury, or disease can cause pain and disability.