An abnormal curvature of the spine

By Jonathan Cluett, MD 

 Medically reviewed by David Kesselman, DC

Scoliosis is an abnormal C-shaped or S-shaped spine curve that is usually found during childhood or early adolescence. It also can occur in older adults, typically in their 60s and 70s, but for different reasons. Scoliosis is usually permanent without medical intervention.

There is more than one type of scoliosis. Most cases are classified as idiopathic scoliosis, meaning the cause is unknown. Affecting between 1% and 3% of adolescents in the United States, this type is often identified through school screening programs or by a family healthcare provider.1

This article discusses the types, causes, and treatment of scoliosis. It explains why an uneven waistline or one shoulder that is higher than the other are signs of the condition and covers possible complications of this abnormal curvature of the spine.

Verywell / Gary Ferster

Normal vs. Abnormal Spine Curvature

Your spine can be divided into three main parts—your neck (cervical spine), your chest and mid-back (thoracic spine), and your lower back (lumbar spine). Vertebrae are the bones that make up each of these areas. They are stacked one upon the other like blocks.

The vertebrae normally form a straight line when looking at your spine from the back. With scoliosis, the vertebrae curve to one side and rotate or twist, making the hips or shoulders appear uneven.

While scoliosis can occur in any part of the spine, the thoracic and lumbar spines are most commonly affected. A sideways curvature or "C" shape of the thoracic or lumbar spine forms.

Less commonly, the spine may curve twice (once in the neck and once in the lower back) and form an "S" shape.

Scoliosis Symptoms

Here are some of the more common signs of scoliosis:2

• Uneven shoulders, arms, rib cages, and/or hips (meaning one is higher than the other)

• One shoulder blade sticking out farther than the other

• Apparent lean of the body to one side

• Head that doesn't seem like it is centered right above the pelvis

Does Scoliosis Cause Back Pain?

Scoliosis typically is not associated with severe back pain, though it can be. Studies show that 38% of children with scoliosis experience it, which is a higher rate than was previously thought.3 Still, it's important to consider all possible causes of back pain if it occurs.

Complications

If scoliosis progresses without treatment, the spine deformity may press on adjacent nerves, leading to weakness, numbness, and electric shock-like sensations in the legs.

Walking or posture abnormalities may also occur. Rarely, if the lungs are unable to expand due to related ribcage deformity, breathing problems may occur.

Complications may also arise from treatment and differ based on the scoliosis type. For example, people with congenital (present at birth) scoliosis treated with spinal fusion surgery may have a higher risk of breathing-related problems from the procedure than those diagnosed with idiopathic scoliosis.4

Older people may develop pain and mobility issues later in life as their spinal cord becomes affected by age-related degenerative changes and/or a neuromuscular condition. Osteoporosis may contribute to these scoliosis cases, too.

Infection and other complications after scoliosis surgery are common in older adults, with nearly 80% of the 92 participants in one study experiencing them.5

Causes of Scoliosis

Experts generally divide the causes of scoliosis into three main categories due to their underlying causes—idiopathic, congenital, and neuromuscular.

In all cases, scoliosis is not preventable.

Idiopathic Scoliosis

Idiopathic scoliosis is the most common form of scoliosis, accounting for around 85% of cases.6 Though the precise cause of this type is unknown, experts believe genetics may play a role in some people.

Idiopathic scoliosis is further classified by age group:

• Infantile (birth to 2 years)

• Juvenile (3 to 9 years)

• Adolescent (10 years or older): This is the most common subtype of scoliosis. It occurs at the growth spurt of puberty.

• Adult: A progression of adolescent idiopathic scoliosis

Congenital Scoliosis

Congenital scoliosis is rare and the result of abnormal development of the vertebrae. For instance, one or more vertebrae may fail to form or not form as expected.

This type is present at birth, but the actual lateral curve of the spine that defines scoliosis may not develop till later in life.

While congenital scoliosis may occur on its own, it's sometimes associated with other health issues, such as bladder, kidney, or nervous system problems.7

Examples of such syndromes include:

• Marfan syndrome, a condition affecting the heart, eyes, and skeletal structure

• Ehlers-Danlos syndrome, a joint and skin tissue disorder

• Osteochondrodystrophy (dwarfism)

• Neurofibromatosis type 1, tumor growths around nerves

Neuromuscular Scoliosis

Neuromuscular scoliosis is due to an underlying nervous or muscular system disorder. Spine curvature occurs because various nerves and muscles cannot maintain proper spine alignment.

Examples of conditions commonly associated with neuromuscular scoliosis include:8

• Cerebral palsy, affecting muscle control and other functions early in life

• Spina bifida, a birth defect caused by the spinal column not closing properly

Spinal cord injury also can lead to neuromuscular scoliosis.

Other Causes

Besides idiopathic, congenital, and neuromuscular scoliosis, there are two additional categories that scoliosis may fit into:9

Degenerative Scoliosis

This is most common in people aged 65 or older. It occurs when joints and discs of the spine break down due to wear and tear.

Degenerative scoliosis most often occurs in the lower part of the back. It may be associated with back pain and nerve symptoms like tingling and/or numbness.

Functional Scoliosis

This type occurs when there is a problem with another part of the body that is making the spine appear curved, even though its structure is normal.

For example, a discrepancy in leg length can make the spine seem curved, as can muscle spasms and inflammation from appendicitis or pneumonia.

With functional scoliosis, the curve will go away once the underlying problem is fixed. Since the spine is normal, no specific spine treatment is ever needed. This sets this type of scoliosis apart from the others.

Diagnosis

If you suspect scoliosis, make an appointment with your healthcare provider. You may be referred to a professional who specializes in spine disorders, like an orthopedic surgeon or physiatrist.

The diagnosis of scoliosis is generally made from a review of a medical history, a physical exam, and one or more imaging tests.2 The extent of the curve of your spine will be measured.

A slight degree of lateral curvature is not necessarily abnormal. One that is less than 10 degrees is within normal limits.

Medical History

During the medical history, a healthcare provider will inquire about your past medical history, family history, and when you first noticed problems with the spine.

They will also ask about symptoms, including whether they cause emotional distress and/or affect daily activities.

Physical Examination

During the physical exam, the healthcare provider will carefully look to see if:

• The vertebral column curves or bends from side to side

• There is a rotational or twisting spine deformity (which may be subtle)

• There is unevenness in your shoulders, arms, hips, and ribs

To do this, a practitioner will perform the Adam's forward bend test.2 You are observed from the back while you bend forward at the waist until your spine is parallel to the floor.

The test is positive if an asymmetry is present, like if a rib sticks out on one side of the body but not the other (called a "rib hump").

After inspection of the spine, the provider will use a tool called a scoliometer to determine the angle of trunk rotation (ATR).

While in the same bent position, the scoliometer is run along your spine from top to bottom. If the measurement it registers is 10 degrees or greater, an imaging test is required.

Imaging Tests

Various imaging tests may be used to diagnose scoliosis. Healthcare providers almost always start with an X-ray, where the Cobb angle—a measurement of the spine curvature—is calculated. A Cobb angle of at least 10 degrees is necessary to diagnose scoliosis.10

Besides measuring the Cobb angle, imaging tests like magnetic resonance imaging (MRI) of the spine may be used to better visualize the spinal curvature and diagnose a specific type of scoliosis, such as degenerative scoliosis.

Children with congenital scoliosis may have an increased risk of having other body system abnormalities. Because of this, additional imaging tests—such as an ultrasound of the kidneys or bladder (called a renal ultrasound) or the heart (called an echocardiogram)—may be recommended.

Treatment

Scoliosis treatment has been the cause of debate for many years. As such, all cases do not have a definitive course of action.

The treatment of scoliosis also really varies from person to person, depending on the following:

• Age

• Curve severity

• Likelihood of the curve worsening

• Impact on quality of life and daily functioning

For instance, mild scoliosis generally requires no treatment. However, scoliosis that causes breathing problems does.

The three main scoliosis treatment options are observation, bracing, and surgery.11

Observation

Patients are observed when the curvature of the spine is minimal. The cutoff is debatable, but depending on someone's age, stage of skeletal development, and symptoms, it is somewhere between 20 and 30 degrees of curvature.

Over this cutoff, more aggressive scoliosis treatment is usually pursued.

People with mild curvature that doesn't interfere with their life and health may be monitored by a spine specialist about every six months until skeletal maturity is reached.

Bracing

Braces can help control any worsening of spine curvature but do little to correct an existing deformity. Bracing is most effective for scoliosis treatment when used in rapidly growing children with worsening scoliosis curves.

Surgery

Surgery is often the best option for more severe scoliosis. Different surgical procedures may be performed depending on the site of the curve, its degree, a patient's specific symptoms, and the type of scoliosis.

• Spinal fusion is a procedure in which a surgeon joins vertebrae to put them in a more normal anatomic position.

• Microdecompression is a minimally invasive procedure that helps relieve pressure on nerves. Since this option may worsen your curve, especially if it is greater than 30 degrees, this procedure is usually only done at one vertebral level.

• Surgical stabilization entails using various instruments—screws, wires, anchoring hooks, and rods—to stabilize the spine so it can fuse in the correct position.

• Osteotomy involves removing and realigning vertebrae to allow for proper spine alignment.

For congenital scoliosis, a surgeon may recommend surgery in which growth rods are attached to the spine above and below the curve. These growth rods correct the spine as it continues to grow.

Other Treatment Options

Studies are investigating the effectiveness of many other scoliosis treatments, including:11

• Electrical stimulation

• Chiropractic manipulation

• Physical therapy

Evidence for these therapies is mixed. Still, some people may find that one or more of these therapies provide relief.

Summary

Scoliosis is a condition in which the spine becomes curved and, in some cases, twisted. It is most often found during early adolescence, with signs that include skeletal or gait (walking) changes.

Most cases of scoliosis can't be traced to a specific cause. Other types are diagnosed at or shortly after birth or later in life for older adults.

It's important to remember that not every person with scoliosis needs treatment. Some may only be closely monitored while their bones are still growing. Braces, surgical interventions, or other therapies may be used for those who do require treatment.

Sources

Kuznia AL, Hernandez AK, Lee LU. Adolescent Idiopathic Scoliosis: Common Questions and Answers. Am Fam Physician. 2020 Jan 1;101(1):19-23. PMID: 31894928.

American Association of Neurological Surgeons. Scoliosis

Wong C. Treatment of painful scoliosis. Ugeskr Laeger. 2019 Apr 8;181(15):V06180449. PMID: 30990160.

Yin S, Tao H, Du H, Feng C, Yang Y, Yang W, et al. Postoperative pulmonary complications following posterior spinal instrumentation and fusion for congenital scoliosis. PLoS One. 2018 Nov 16;13(11):e0207657. doi:10.1371/journal.pone.0207657. 

Simon MJK, Halm HFH, Quante M. Perioperative complications after surgical treatment in degenerative adult de novo scoliosis. BMC Musculoskelet Disord. 2018 Jan 10;19(1):10. doi:10.1186/s12891-017-1925-2. 

Horne JP, Flannery R, Usman S. Adolescent idiopathic scoliosis: diagnosis and management. Am Fam Physician. 2014;89(3):193-8.

Boston Childlren's Hospital. Congenital Scoliosis

American Academy of Orthopaedic Surgeons. OrthoInfo. Neuromuscular Scoliosis

Weill Cornell Medicine. Center for Comprehensive Spine Care. Scoliosis: Symptoms, Types & Treatments

Wang J, Zhang J, Xu R, Chen TG, Zhou KS, Zhang HH. Measurement of scoliosis Cobb angle by end vertebra tilt angle method. J Orthop Surg Res. 2018;13(1):223. doi:10.1186/s13018-018-0928-5

Karimi MT, Rabczuk T. Scoliosis conservative treatment: A review of literature. J Craniovertebr Junction Spine. 2018;9(1):3-8. doi:10.4103/jcvjs.JCVJS_39_17

Additional Reading

American Association of Neurological Surgeons. (2019). Scoliosis.

Children's Hospital of Philadelphia. (2019). Congenital Scoliosis.

Dewan MC, Mummareddy N, Bonfield C. The influence of pregnancy on women with adolescent idiopathic scoliosis. Eur Spine J. 2018 Feb;27(2):253-63. doi:10.1007/s00586-017-5203-7

Hey LA. (2018). Scoliosis in the adult. Atlas SJ, ed. UpToDate. Waltham, MA: UpToDate Inc.

Horne JP, Flannery R, Usman S. Adolescent Idiopathic Scoliosis: Diagnosis and Management. Am Fam Physician. 2014 Feb 1;89(3):193-98.

Scoliosis Research Society. (2019). Scoliosis.

By Jonathan Cluett, MD
Dr. Cluett is board-certified in orthopedic surgery. He served as assistant team physician to Chivas USA (Major League Soccer) and the U.S. national soccer teams.