Scoliosis is a lateral (sideways) curvature of the spine associated with rotation so that in the thoracic spine the ribs on the convex side are displaced backwards. It is very common with 25 per cent of the population having some degree of spinal asymmetry in childhood. Curves over 20° occur in 1-2 per thousand boys and 4-5 per thousand girls. 65 per cent of all cases are idiopathic (cause not known). Most scoliosis occurs in girls at the start of adolescence.

When idiopathic curvature occurs at or shortly after birth (infantile curves), the ratio is reversed and boys are often slightly more affected than girls. Interestingly, adolescent curve tends to be more convex to the right whereas infantile ones are to the left. In babies early diagnosis and treatment is particularly important.