The human spine consists of 24 vertebrae. There are 7 cervical (neck), 12 thoracic (chest region), 5 lumbar (lower back), sacrum and 2 ilia (pelvic bones), and coccyx (tailbone). The vertebrae are held in place by muscles and strong connective tissue called ligaments. Most vertebrae have fibrous intervertebral disks between them to absorb shock and enable the spine to bend. It is often this disc as well as other ligaments of the spine that may swell when inflammed and actually "pinch" or place pressure on one of the 31 pairs of nerves that exit the spinal cord through the vertebral column.

The spine normally has a slight curve. Abnormal curvatures may be present at birth. They may also result from injury, repetitive stresses, disease, poor posture, or a strain on the muscles attached to the spine. Scoliosis occurs when the spine curves sideways. Kyphosis, or hunchback, is a forward bending of the thoracic vertebrae that often affects elderly people. Lordosis, or swayback, is an exaggerated curvature of the lumbar vertebrae. It usually affects overweight people and pregnant women.

With improper maintenance damage to the spine often occurs in the cervical and lumbar regions. Fractured cervical vertebrae may injure the spinal cord, resulting in a loss of sensation, paralysis, or even death. Whiplash is an injury to the muscles and ligaments attached to cervical vertebrae. It occurs when a sudden force—such as a rear-end car accident—throws the head backward then forward. As injuries occur to the spine, the inner part of an intervertebral disk is likely to stick out through the outer part. This is called a buldged or herniated disk. A buldged or herniated disk in the lower back may pinch nerves, causing low back pain, sciatica (pain shooting down the leg) or numbness in the lower extremities. A herniated disk in the lower neck may cause neck pain, headaches or pain/numbness in the shoulder or down into the arm or hand.