Scoliosis is the abnormal curvature of the spine. Normally, the spine runs in a straight line from the neck down the back. With scoliosis, however, the spine curves to the side. This can cause the spine to be shaped like a “C” or an “S.” Scoliosis can affect the upper (thoracic) and/or lower (lumbar) portions of the spine.

While scoliosis can affect people at any age, it most commonly begins in children between ages 10 and 15. According to the National Scoliosis Foundation, scoliosis is estimated to affect 7 million people in the United States—around 2% to 3% of the population.

Often, the amount of spinal curvature is mild and doesn’t cause symptoms or require any special treatment beyond regular monitoring. Less commonly, however, the curve can be severe, causing back pain and making breathing difficult. Fortunately, treatments can improve the condition, including braces, physical therapy, and surgery.

Scoliosis is an abnormal sideways curvature of the spine that also twists abnormally. The side-to-side curvature can cause changes in posture, such as uneven shoulders and/or hips, while the twisting of the spine can cause the rib cage on one side of the body to protrude more than usual.

Often, the curve of the spine in people with scoliosis is stable, meaning it does not change over time. Sometimes, however, it worsens over time, often requiring treatment. For example, the curve of the spine may become more severe in adolescents undergoing periods of rapid growth during puberty. Also, in general, spines with a greater degree of curvature are at a higher risk of progressing.

Scoliosis most commonly starts in childhood or adolescence but can also occur in infants and adults. In adults, the condition may have first developed during childhood or adolescence and then continued to progress into adulthood. In other cases, scoliosis can develop in adulthood due to degenerative changes to the spine, osteoporosis, neuromuscular disorders, injury, or other medical conditions.

There are several types of scoliosis, including:

• Idiopathic scoliosis. An “idiopathic” medical condition is one for which there is no known cause. Idiopathic scoliosis is the most common type, accounting for roughly 80%-90% of cases. It equally affects boys and girls, but when it occurs in girls, it is 10 times more likely to progress. Idiopathic scoliosis is further categorized based on the age at which the condition first occurred.
  • Infantile idiopathic scoliosis occurs in children between ages 0 and 3 years.
  • Juvenile idiopathic scoliosis occurs in children between ages 4 and 9 years.
  • Adolescent idiopathic scoliosis occurs in children and adolescents between ages 10 and 18.
• Congenital scoliosis. In this type of scoliosis, spinal curvature occurs due to spine abnormalities that are present at birth.
• Neuromuscular scoliosis (NMS). This type of scoliosis occurs in people with disorders that affect the muscles and/or nerves, including cerebral palsy, Duchenne muscular dystrophy, or a spinal cord injury. It can begin in people of any age.
• Degenerative scoliosis. This type of scoliosis is due to degenerative changes to the spine; it usually affects adults over 50.

When scoliosis occurs in children under 10, it is sometimes called early-onset scoliosis (EOS).

Most people with mild scoliosis have no symptoms, though some experience back pain.

Signs of scoliosis may include:

• A curved spine
• One shoulder and/or hip that is higher than the other
• One shoulder blade that is more prominent than the other
• A ribcage on one side that protrudes more than the other side (it may be more noticeable when bending over)
• A person’s head that is not centered over their pelvis
• Extra space between the body and a loosely hanging arm on one side of the body

People with severe scoliosis, with greater degrees of spinal curvature, may have difficulty breathing and back pain. The breathing problems occur, in part, because the chest cannot fully expand during inhalation and exhalation. People with scoliosis as well as spinal cord or nerve root compression caused by kyphosis (a forward curve of the upper spine that causes a hunched back) and/or a spinal cord abnormality in addition to scoliosis may have additional symptoms, including:

• Incontinence (loss of bladder/bowel control)
• Weakness or numbness in the legs
• Erectile dysfunction

Doctors diagnose scoliosis by reviewing a patient’s medical history, performing a physical exam, and running one or more diagnostic tests. Scoliosis may first be detected during routine screenings at middle schools or at checkups with primary care doctors.

The doctor will ask about symptoms and the patient’s spinal curve, including when it was first noticed and whether it has worsened over time. They may also ask whether there is a family history of scoliosis.

During a physical exam, the doctor will examine the patient’s back and spine to check for a curvature of the backbone, differences in the level of the shoulders and hips, whether the head is centered over the pelvis, and other signs of scoliosis. The doctor will ask the patient to bend forward to check whether the ribs on one side of the body or other parts of the back stick out more than usual. During this test, known as the Adams forward bend test, the doctor may use a sociometer—a device similar to a level—to measure the degree of spinal rotation.

X-rays of the spine are needed to confirm a diagnosis. They also help doctors determine the type of scoliosis and the risk of its progression. The doctor will use the X-rays to determine the Cobb angle, a measure of the degree of sideways spinal curvature. (Scoliosis is diagnosed when the Cobb angle is over 10 degrees.) In some cases, the doctor may also order additional imaging tests, such as a magnetic resonance imaging (MRI) scan or computed tomography (CT) scan of the spine.

The outlook can vary greatly and depends on a number of factors, including the age when the condition began, the age at diagnosis, the severity of the spinal curve, whether the spinal curvature is stable or progressing, and the underlying cause of the condition.

People with mild scoliosis typically do not experience any symptoms and do not need treatment. In some cases, however, treatment is necessary to reduce the spinal curve and prevent progression of the condition. With appropriate treatment, most people with scoliosis can lead physically active, normal lives.

This article was medically reviewed by Dominick Tuason, MD, a Yale Medicine pediatric orthopedic surgeon with a subspecialty in early onset, adolescent, neuromuscular, and complex spinal deformity.