Causes
The vast majority of adolescent scoliosis is idiopathic, meaning its cause is unknown. Although the causes of this condition have not been discovered, there are several theories as to why it develops. Genetics is one subject of ongoing research, since scoliosis appears to be hereditary. Curves rapidly advance during growth spurts, which may indicate hormonal causes. Structural and biomechanical changes may also be a factor since different leg lengths have been observed and increased muscular activity can be found around spinal curves. Additionally, equilibrium has been shown to affect body alignment. Posture, balance and body symmetry could affect the way the spine is positioned and may disrupt how muscles develop.

Central nervous system disorders—such as cerebral palsy, poliomyelitis, muscular dystrophy, spina bifida, tumors or trauma such as a spinal cord or brain injury—have also been associated with some forms of scoliosis.

Congenital abnormalities of the spinal cord and vertebrae can also lead to scoliosis. In these cases, children in the mother’s uterus have been put at risk by drugs, medications, infection or environmental causes. This can cause the vertebrae to fuse together or become malformed, leading to very severe curves. In congenital cases, the underlying spinal cord can also form incorrectly.

Likelihood of Progression
Once scoliosis is diagnosed, there is no definite way to tell whether the curves will continue to increase. However, curves in the thoracic spine are more likely to progress than lumbar curves. Also, the likelihood of progression is linked to the size of the curve, so larger curves are more likely to get bigger. Curves beginning at a young age are also more likely to progress.

A Risser sign is a measure of skeletal maturity based on a layer of cartilage on the hipbone that turns to bone as children age. The higher a child’s Risser sign at the time of diagnosis, the less chance there is of progression.