About Scoliosis

Adolescent idiopathic scoliosis is a sideways curve of the spine that appears in the teenage years, with no single known cause. Most curves are small and stay small. It isn't anyone's fault, and it usually doesn't hurt.

Reviewed by Dr. Kshitij Chaudhary — Last reviewed October 2026

What is adolescent idiopathic scoliosis?

Scoliosis is a sideways curve of the spine. Seen from behind, a healthy spine runs straight down the middle of the back. In scoliosis, part of the spine bends to the right or left, and the bones also twist a little. That twist is why one side of the ribcage can stick out more and the waist can look uneven.

On an X-ray, we measure the curve as an angle called the Cobb angle. A curve of more than 10 degrees counts as scoliosis. About 1 in 10 people have smaller curves, which make no difference to health.

"Idiopathic" means we don't know the exact cause. "Adolescent" means it starts from around age 10, when growth speeds up. Younger children can get idiopathic scoliosis too (infantile, up to age 3, and juvenile, from 4 to 9), but those are managed differently.

The most common pattern is a curve to the right in the upper back (the thoracic spine). Curves can also sit in the lower back (lumbar spine) or where the two meet, and some children have a double, S-shaped curve.

(Image to add: X-ray with Cobb angle measured, and a diagram of a straight spine next to a curved one)

What causes it?

It's mostly genetic. About 3 in 10 teenagers with scoliosis have a relative with it, and it can skip a generation. Researchers haven't found one single gene. One leading idea is that the front and back of the vertebrae grow at slightly different speeds, which tilts and twists the spine.

What does not cause it: heavy school bags, poor posture, sitting habits, sport, diet, or not drinking enough milk. Nothing you or your child did or didn't do caused it.

How common is it, and who gets it?

About 2 to 3 in every 100 adolescents have scoliosis. Most of these curves are small. This table shows roughly how many young people have curves of each size.

Boys and girls are equally likely to have a small curve. Girls are five to eight times more likely than boys to have a curve that gets bigger.

How serious is it?

For most families, the honest answer is: not very. Most curves are small and stay small. Scoliosis is rarely dangerous, it almost never needs urgent action, and it usually causes no pain in teenagers.

The reason we watch and treat curves is to stop them growing big enough to cause trouble in adult life. Very large curves (over 70 to 80 degrees) that are left alone for many years can affect breathing, heart and muscle strength, and can cause back pain. Careful follow-up, and bracing or surgery when needed, prevent this.

What are the signs?

Parents, teachers, coaches and doctors usually notice one or more of these:

• One shoulder higher than the other
• One shoulder blade sticking out more
• One hip higher than the other, or one leg looking longer
• An uneven waist
• The trunk or ribcage shifted to one side
• The head not sitting centred over the hips
• Clothes hanging unevenly
• One side of the back looking higher when your child bends forward at the waist

(Image to add: back views showing shoulder asymmetry, trunk shift, waist asymmetry and rib prominence on forward bend)

To check at home, ask your child to stand with feet together, bend forward from the waist and let the arms hang. Look along the back from behind. A bump on one side of the ribs or lower back is called a rib hump. Seeing one doesn't confirm scoliosis, but it's a good reason to get your child examined.

Why didn't we notice it sooner?

This is one of the most common questions we hear, and it's not a failing on anyone's part. The body changes fast in the early teens. Teenagers become more private, so parents rarely see their backs. Early changes can be subtle, and a curve can be significant even when the back looks almost normal. Scoliosis also doesn't usually hurt, so there's nothing to draw attention to it. Sometimes it's found by chance on an X-ray done for another reason.

Does scoliosis hurt?

Usually not. Teenagers with mild to moderate scoliosis don't have more back pain than other teenagers. Larger curves can occasionally cause some discomfort. A heavy school bag can cause aches, so keep the load light and use both shoulder straps.

Are there other kinds of scoliosis?

Yes. Idiopathic scoliosis is the most common kind, and we make sure at the first visit that nothing else is behind it. The other main types are:

• Neuromuscular: linked to a condition such as cerebral palsy, muscular dystrophy or spina bifida. See ◾Neuromuscular Scoliosis
• Congenital: present from birth, when some vertebrae didn't form or separate normally
• Syndromic: part of a wider condition such as Marfan syndrome or neurofibromatosis
• Secondary: after chest surgery, tumour treatment or radiation

This information is for general education and does not replace a consultation with your doctor.