Scoliosis (pl.: scolioses) is a medical condition in which the spine has an irregular curve in the coronal plane. The curve is usually S- or C-shaped over three dimensions. In some, the degree of curve is stable, while in others, it increases over time. Mild scoliosis does not typically cause problems, but more severe cases can affect breathing and movement. Pain is usually present in adults, and can worsen with age. As the condition progresses, it may alter a person's life, and hence can also be considered a disability. It can be compared to kyphosis and lordosis, other abnormal curvatures of the spine which are in the sagittal plane (front-back) rather than the coronal (left-right).
The cause of most cases is unknown, but it is believed to involve a combination of genetic and environmental factors. Scoliosis most often occurs during growth spurts right before puberty. Risk factors include other affected family members. It can also occur due to another condition such as muscle spasms, cerebral palsy, Marfan syndrome, and tumors such as neurofibromatosis. Diagnosis is confirmed with X-rays. Scoliosis is typically classified as either structural in which the curve is fixed, or functional in which the underlying spine is normal. Left-right asymmetries, of the vertebrae and their musculature, especially in the thoracic region, may cause mechanical instability of the spinal column.