Adolescent idiopathic scoliosis

Scoliosis is a fixed lateral curvature (deformity) of the spine. There are several causes of scoliosis, the most common of which is adolescent idiopathic scoliosis (AIS). AIS generally appears during the adolescent growth spurt and is more common in girls than in boys. Current research has focused attention on a genetic cause, since AIS often runs in families. It is generally diagnosed between the ages of 10 and 15, and the child is otherwise normal and healthy.

Anatomy of the spine

When viewed from the side, the normal spine should have a gentle S curve. The upper portion should be gently rounded forward and is called “kyphosis.” The lower part of the spine is gently rounded inward (swayback) and is called “lordosis.” However, when viewed directly from the back, a normal spine should be straight. Sometimes a difference in leg lengths can cause the spine to look crooked, so your doctor should check for this.


Recent evidence suggests that there is often a positive family history in patients who exhibit the disease, and thus the disease is genetically transmitted. However, it often skips generations and is probably related to many genes. It likely takes a number of these genes in combination to create a spine that will curve.


Most patients with AIS do not have pain or any other symptoms. Symptoms of severe back or leg pain, numbness or weakness of the legs, or difficulty controlling toileting are generally not associated with AIS, and their presence should alert the physician to look for other causes of the scoliosis.

Adolescent idiopathic scoliosis symptoms are not limited to the physical. Psychological effects and negative self-image tend to go along with a progression of the disease as well. This is particularly true in progressive cases, where the curvature of the spine is more severe and visible to an observer. This can affect the way that patients view themselves, and thus result in negative associations with their own body image and lack of confidence.


There are three sub-classifications of idiopathic scoliosis: it is classified as adolescent if the onset of the disease occurred at the age of 10 or older, juvenile if it is diagnosed between three and 10 years of age and infantile if it is diagnosed before the age of three years. Eighty percent of all idiopathic scoliosis cases diagnosed are of the adolescent variety.

Risk factors

Researchers have identified risk factors that are likely to be an indication of whether or not the disease will progress to a level that requires treatment. These include:

  • Genetic predisposition of a given patient
  • Curve type
  • Physical maturity of the patient’s bones
  • Location of the curve

While researchers continue to work to find the true cause of this condition, for families and patients who have the disease it is no doubt frustrating not to know the exact cause. However, continued medical and technological advances are steadily improving both the understanding and treatment of the disease.

Tests and diagnosis

For scoliosis to be diagnosed, there must be at least 10 degrees of fixed lateral curvature of the spine. This is a measurement made on an X-ray. AIS affects 2.5 percent of the population. While small curves are almost evenly distributed between girls and boys, it is interesting to note that the larger curves are more common in girls. 

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