A normal spine, when viewed from behind, appears straight. However, a spine affected by scoliosis shows evidence of a lateral, or side-by-side curvature, with the spine looking like an "S" or "C" and a rotation of the back bones (vertebrae), giving the appearance that the person is leaning to one side. The Scoliosis Research Society defines scoliosis as a curvature of the spine measuring 10 degrees or greater.In over 80 percent of cases, the cause of scoliosis is unknown — a condition called idiopathic scoliosis.In this segment, Munish Gupta, MD discusses idiopathic scoliosis and when a pediatrician should refer a patient to St. Louis Children's Hospital.