Heredity and congenital irregularities have emerged as the most probable causes of Scoliosis today.
Abnormalities in development, such as extra or absent ribs and irregularly shaped vertebrae, may cause the spine to curve in an attempt to compensate for the problem. Scoliosis is attributed to heredity more than to any other factor, although genes that carry Scoliosis have not yet been discovered.
At the beginning of the twentieth century, however, there was much debate on the causes of Scoliosis. Many doctors believed that lack of regular exercise resulted in the development of scoliosis in girls. It was thought that since boys participated in more physical activities than girls, they had a lower occurrence of Scoliosis. Girls simply needed to get more exercise to avoid developing Scoliosis. However, doctors rejected this as a treatment. Girls were thought to be too weak and fragile to participate in vigorous activities, thus an increase in physical activity would be unfitting. J.H. Coles, a British writer, claimed that a girl's "spongy, soft [Scoliotic] bones" would harden with exercise, but that innate weakness prevented her from participating in such activities.
The furniture used in school rooms was identified as a cause of Scoliosis by physicians who believed that improper posture increased spinal curvature. Uncomfortable, standard desks forced students to sit at odd angles and children often slouched at their desks. Some believed this caused their spines to bend and grow into curved positions. However, Dr. Arthur Steindler, of the University of Iowa, and Dr. Robert H. Lovett, orthopedists, noted poor posture as a cause for "false Scoliosis," or a normal spine bent into a curved position. They did not believe poor posture or uncomfortable desks caused Scoliosis.
Unequal leg lengths were also blamed for Scoliosis. Some physicians claimed that a patient with uneven leg lengths stood and walked in a slanted posture, which caused the back to become slanted as well. Slanting the spine and shoulders resulted in the development of a curved spine. However, prescriptions for shoes with built-up soles were the supposedly easy solution to this problem.
Physicians believed that long periods of "muscle weakness" could cause Scoliosis. Diseases like polio, and infections that affected the chest muscles were noted as causes for muscle weakness in the back. Weak muscles on one side of the spine, it was thought, caused the strong muscles on the other side to pull the spine out of alignment. Some physicians in the early twentieth century believed this theory and attempted to strengthen the muscles in a patient's back. While keeping the muscles strong was good for the spine, it did not improve curvature or prevent progression.
The late twentieth and early twenty-first centuries disproved theories of corsets, posture, female weakness and unequal leg lengths as causes of Scoliosis. Heredity is believed to influence the development of Idiopathic Scoliosis. Other types of Scoliosis may be caused by abnormal spine or rib development, osteoarthritis, or neuromuscular diseases. Some surgeries, radiation or infections, like polio, may result in post-traumatic Scoliosis. Skeletal dysplasias, syndromes and other spinal diseases can also influence the development of Scoliosis.