any of a group of deviations of the normal spinal curvature, including scoliosis, lordosis, and kyphosis.

Scoliosis is a lateral, or sideways, deviation of the spine, or vertebral column. The condition usually includes two curves—the original abnormal curve and a later-developing compensatory curve. Possible causes of scoliosis include asymmetrical development of back, chest, or abdominal musculature, as may occur in poliomyelitis (polio) or cerebral palsy; significant difference in the lengths of the legs; or malformation or disease of the vertebral column and associated structures, as in spondylitis, spina bifida, fracture, dislocation, hemivertebrae, or rickets. Treatment, which depends on the cause, usually includes orthopedic surgery, the use of traction, the wearing of body or neck braces, and exercises.

Lordosis, or swayback, is an increased curvature in the lumbar (middle-to-lower) region of the vertebral column, and it may be associated with spondylolisthesis, inflammation of the intervertebral disk, or obesity. Kyphosis, commonly called roundback, humpback, or hunchback, is an increased curvature of the thoracic (upper) vertebral column; it may be caused by congenital malformation of the vertebral column, by the development of wedge-shaped vertebrae during adolescence (Scheuermann disease), or by other conditions such as osteoporosis or tuberculous spondylitis (Pott disease).