Scoliosis is a disorder that causes an abnormal curve of the spine, or backbone. The spine has normal curves when looking from the side, but it should appear straight when looking from the front. Kyphosis is a curve seen from the side in which the spine is bent forward. There is a normal kyphosis in the middle (thoracic) spine. Lordosis is a curve seen from the side in which the spine is bent backward. There is a normal lordosis in the upper (cervical) spine and the lower (lumbar) spine. People with scoliosis develop additional curves to either side, and the bones of the spine twist on each other, forming a “C” or an “S” shape in the spine.