Lateral curvatures of the spine less than 10 degrees are generally not referred to as scoliosis. In order to answer this you must first understand that there are several categories into which scoliosis as a general syndrome is separated. The word idiopathic simply means that the cause is not known. Idiopathic scoliosis is further classified by age group. Idiopathic adolescent scoliosis is the most common type of scoliosis.
Congenital scoliosis is the result of an abnormality of the development of the vertebrae.
When the bones of the spine fail to develop normally, a scoliosis deformity can result. Also, some specific congenital syndromes can include a scoliosis deformity. Another category of scoliosis is non-structural, or functional, scoliosis. This occurs when there is a problem with another part of the body that is causing a curve in the spine. For example, a discrepancy in leg length can cause the spine to curve to one side.