Scoliosis are "captured", meaning that they are held fast between the ilium bones of the pelvis. Compared to humans, Old World monkeys have far larger erector spinae muscles, which are the muscles which hold the spine steady. These factors make the lumbar spine of most primates less flexible and far less likely to deviate than those of humans. While this may explicitly relate only to lumbar scolioses, it is possible that small imbalances in the lumbar spine could precipitate thoracic problems as well. Scoliosis may be a byproduct of strong selection for bipedalism. For a bipedal stance, a highly mobile, elongated
Scoliosis drawn perpendicular to the upper endplate of the uppermost vertebra involved and the lower endplate of the lowest vertebra involved. For people with two curves, Cobb angles are followed for both curves. In some people, lateral-bending X-rays are obtained to assess the flexibility of the curves or the primary and compensatory curves. Congenital and idiopathic scoliosis that develops before the age of 10 is referred to as early-onset scoliosis. Scoliosis that develops after 10 is referred to as adolescent idiopathic scoliosis. Screening adolescents without symptoms for scoliosis is of unclear benefit. Scoliosis is defined as a three-dimensional deviation in the