Scoliosis is any abnormal sideways curvature of the spine measuring at least 10 degrees on an x-ray. While scoliosis is not a disease, in rare cases it can be caused by a disease. More often, however, scoliosis develops from an unknown cause during adolescence or from spinal degeneration during adulthood.

Structural vs. Nonstructural Scoliosis

There are two general categories for scoliosis:

  • Structural scoliosis is by far the most common category of scoliosis. It involves spinal rotation in addition to the side-to-side curvature of the spine. This type of scoliosis affects the spine’s structure and is considered permanent unless the spine receives treatment.

    See Scoliosis Treatment

  • Nonstructural scoliosis, also known as functional scoliosis, results from a temporary cause and only involves a side-to-side curvature of the spine (no spinal rotation). The spine’s structure is still normal.

If a person with nonstructural scoliosis were to bend forward or lay down, the scoliosis curve would likely go away while held in that position.

Structural scoliosis is typically considered more serious because it does not straighten out on its own and can potentially result in more spinal deformity.


Types of Structural Scoliosis

There are several types of structural scoliosis, including:

  • Idiopathic scoliosis accounts for about 8 in 10 cases of scoliosis. This type of scoliosis typically presents during adolescence, but it can also start earlier in childhood or infancy. What causes idiopathic scoliosis is currently unknown. Some research indicates genetics plays a part, but other factors are also likely involved and continue to be studied.

    See Scoliosis: Symptoms, Treatment and Surgery

  • Degenerative scoliosis (adult scoliosis is a common condition that occurs later in life as the joints in the spine degenerate. Read more about adult scoliosis.

    See All About Degenerative Scoliosis

  • Neuromuscular scoliosis sometimes develops in individuals who cannot walk due to a neuromuscular condition such as muscular dystrophy or cerebral palsy. This type of scoliosis may also be called myopathic scoliosis.
  • Congenital scoliosis develops in utero and is present in infancy. A rare condition, affecting 1 in 10,000, it can result from malformations in the vertebrae or other causes. In most cases the spinal curve must be corrected surgically.

Rarely, scoliosis is caused by a spinal lesion or tumor. Usually, patients who are younger (age 8 to 11) than typical scoliosis patients will experience symptoms such as pain, numbness and a left-curving thoracic spine. A physician who sees any or a combination of these symptoms will order additional diagnostic tests, such as an MRI, to rule out the possibility of spinal tumor or other lesions as a cause of scoliosis.

See Scoliosis Diagnosis


Common Causes of Nonstructural Scoliosis

While non-structural scoliosis is relatively uncommon, here are some ways it can occur:

  • Muscle spasms. If a major muscle in the back starts to spasm, the spine could be pulled in one direction and a sideways curve may result.
  • Difference in leg heights. When one leg is significantly longer than the other, a scoliosis curve may be present while standing.
  • Inflammation. If an area of the body to one side of the spine or the other starts to become inflamed, a scoliosis curve can result. Some possible causes could be appendicitis or pneumonia.

Watch Causes of Back Muscle Spasms Video

Once the underlying cause of a nonstructural scoliosis is treated, the scoliosis will also go away.

Dr. Ali Baaj is the Chief of Spine Surgery at Banner Health and the Associate Professor of Neurological & Orthopedic Surgery at the University of Arizona. He specializes in complex and minimally invasive spine surgery for adults and children.