Scoliosis is a curvature of the spine most commonly starting in childhood or adolescence. The cause can be a muscle imbalance from cerebral palsy or other muscle problems, a birth defect, an injury, or sometimes there is scoliosis that runs in the family and is hereditary. Occasionally it is caused by a difference in the length of the two legs.
The curvature is sometimes accompanied by a rotation of the spine, and will produce an asymmetry of the back. Perhaps one shoulder blade is higher than the other or one shoulder is lower than the other. Differences in the leg length can be seen by differences in height of the pelvis.
The problem can be silent, if mild. However it can affect the way the child walks, or even interfere with breathing if severe. If untreated and progressive, it can cause chronic back pain in adulthood. Treatment is accomplished by braces, or occasionally by screws placed in the side of the vertebra that can be adjusted.
I had a friend that was 70 years old whose back pain eventually forced surgery. Scoliosis should definitely be supervised by a Doctor who will use physical therapy, braces, or some other conservative treatment to avoid later difficulties.
Please refer to the Mayo clinic article for more information.