This is a lateral spinal curvature with a 3-dimensional component with rotation of the vertebrae. This is the most common type of scoliosis affecting about 3-4% of the adolescents in the early stages of puberty. It is more common in girls (over 75% of the patients) than boys. It has no known cause and genetic researches are under way. People with relevant family medical history have a higher risk of developing scoliosis.

Based on the size of the curve on a spine x-ray, scoliosis can be considered as mild, moderate or severe.

Common misconceptions about the cause adolescent idiopathic scoliosis include poor standing or sitting posture, weight of schoolbags or carrying heavy objects, sports or physical activities. These may aggravate but they are not the cause of the curve.