Scoliosis

Scoliosis is a sideways curvature of the spine, often combined with a degree of rotation, that causes the spine to curve to the side rather than running in a straight vertical line when viewed from the front or back. Viewed from the side, a healthy spine has natural front-to-back curves that help absorb shock and support the body's weight — scoliosis specifically refers to an abnormal side-to-side curve, and is formally defined as a curve of at least 10 degrees, measured using a specific method called the Cobb angle, described further below.

Scoliosis most commonly appears in children and adolescents, particularly during the rapid growth period around puberty, but it can also develop in adults, sometimes for entirely different reasons. Most cases are mild and cause no pain, but in a smaller number of cases, the curve can progress over time, and if left unmonitored, more severe curves can occasionally affect the space available for the heart and lungs. Understanding what type of scoliosis is present, how severe the curve is, and whether it is likely to progress, is central to deciding on the right monitoring or treatment plan.

How Scoliosis Is Measured: The Cobb Angle

The severity of scoliosis is measured using the Cobb angle, calculated from an X-ray of the whole spine taken while standing. To measure it, lines are drawn along the top of the uppermost tilted vertebra and the bottom of the lowest tilted vertebra of the curve, and the angle formed between these two lines is the Cobb angle. This single number is the foundation for nearly every decision in scoliosis care — whether a curve simply needs monitoring, whether bracing is appropriate, or whether surgery should be considered.

A curve under 10 degrees is technically considered normal spinal asymmetry rather than scoliosis. As a general guide, curves between 10 and 25 degrees are usually monitored, curves between 25 and 40 degrees in a growing child are often considered for bracing, and curves beyond 45 to 50 degrees — particularly in someone still growing — are more likely to be discussed for surgery.

These thresholds are general guides rather than fixed rules, and the decision in any individual case also depends on the type of curve, its location, the amount of growth remaining, and how quickly it has been changing.

Types of Scoliosis

Scoliosis is not a single condition but a description of a curved spine that can arise from several distinct underlying causes, and the type present has a significant bearing on how the condition behaves and is treated.

• Idiopathic Scoliosis: The most common type, accounting for the large majority of cases, in which no specific cause can be identified. Classified by the age it is first noticed: infantile (birth to age 3), juvenile (ages 4 to 9), and adolescent (ages 10 to 18) — adolescent idiopathic scoliosis is by far the most common form overall, typically appearing around the growth spurt of puberty.
• Congenital Scoliosis: Caused by abnormal development of the spine's vertebrae before birth, such as vertebrae that failed to form fully or fully separate from one another. Present from birth, though it may not become noticeable until later, and is often associated with other congenital abnormalities affecting the heart, kidneys or spinal cord that may need to be assessed alongside it.
• Neuromuscular Scoliosis: Occurs secondary to an underlying condition affecting the muscles or nerves that support the spine, such as cerebral palsy, muscular dystrophy, or spinal cord injury. Tends to produce a long, sweeping C-shaped curve rather than the S-shaped curve typical of idiopathic scoliosis, and can progress more rapidly and become more severe, often requiring closer monitoring.
• Degenerative (Adult-Onset) Scoliosis: Develops later in life, typically in the lower back, as a result of age-related changes such as disc degeneration, facet joint arthritis, or vertebral compression fractures related to osteoporosis. Distinct from a childhood curve that has persisted into adulthood, as it develops from wear and tear on a previously straight spine.
• Functional (Postural) Scoliosis: The spine appears curved on examination, but the underlying spinal structure is actually normal — the apparent curve is usually caused by something outside the spine itself, such as a difference in leg length or muscle spasm. Addressing the underlying cause typically resolves the apparent curve, and it is generally not associated with progressive spinal deformity.

How Scoliosis Is Often First Noticed: Screening and Signs

Because scoliosis usually does not cause pain, particularly in its early stages, it is often first noticed by a parent, teacher, or during a routine physical examination or school screening, rather than because of any symptom the individual themselves feels.

• Adam's forward bend test: A simple, widely used screening test in which the individual bends forward at the waist with arms hanging down and knees straight, allowing an examiner to view the back from behind. A rotational rib or waist prominence on one side — caused by the rotational component of scoliosis — is often more visible in this position than when standing upright.
• Scoliometer: A handheld device sometimes used alongside the forward bend test to measure the angle of trunk rotation, helping to decide whether a referral for X-ray imaging is warranted.

Outside of formal screening, several visible signs can point to scoliosis and are worth having assessed by a doctor.

• One shoulder appearing higher than the other, or shoulder blades that are not level
• One hip appearing higher, or more prominent, than the other
• The head not appearing centred directly above the pelvis
• An uneven waistline, or one side of the ribcage appearing more prominent than the other, particularly when bending forward
• The body appearing to lean noticeably to one side overall
• Clothes or hemlines that appear to hang unevenly

If one or more of these signs is noticed, it is worth arranging a screening assessment, as early detection allows monitoring to begin while a curve is still small and more treatment options remain available.

Symptoms of Scoliosis

Many people with scoliosis, particularly with milder curves, have no symptoms at all beyond the visible changes described above. When symptoms do occur, they can include the following.

• Back pain, though this is not the primary feature of scoliosis in most cases, particularly in adolescents, and other causes are usually considered if pain is significant
• Difficulty standing fully upright, or noticeable fatigue in the back muscles after standing or sitting for a period
• Visibly weaker core or back muscles on one side
• Leg pain, numbness or weakness, particularly in degenerative scoliosis where nerve compression can develop alongside the curve
• Gradual loss of height, and increasingly uneven alignment of the pelvis and hips, which may become more noticeable over time in adults
• In more severe curves, shortness of breath or reduced exercise tolerance, if the ribcage's capacity to expand for breathing is significantly affected

Causes of Scoliosis

The cause of scoliosis depends heavily on its type, and for the most common form, a clear single cause is often never identified.

• Unknown (idiopathic) factors: The exact cause of adolescent idiopathic scoliosis, the most common form, is not known, though it is thought to involve a combination of genetic factors (it often runs in families), growth-related changes, and possibly subtle differences in bone, muscle or nervous system development — an active area of ongoing research.
• Neuromuscular conditions: Conditions affecting the muscles and nerves, such as cerebral palsy or muscular dystrophy, can affect the muscles that support and stabilise the spine, allowing a curve to develop and often progress.
• Congenital spinal abnormalities: Abnormalities in how the bones of the spine form before birth can result in a spine that is structurally uneven from an early age.
• Previous surgery in infancy: Certain surgical procedures performed in infancy, such as surgery on the chest wall, or surgery involving removal of bone at the back of the spine, can occasionally affect the future growth and alignment of the spine.
• Age-related degeneration: In adults, degeneration of the spinal discs and facet joints, along with osteoporosis-related vertebral compression fractures, can cause a previously straight spine to gradually curve over time.

Will the Curve Get Worse? Understanding Risk of Progression

One of the most important — and most frequently asked — questions in scoliosis care is whether a particular curve is likely to worsen over time. Several specific factors help predict this, and they are central to deciding how closely a curve needs to be monitored.

• Growth remaining: The single biggest factor. Curves tend to progress fastest during periods of rapid growth, particularly the adolescent growth spurt, and the risk of progression drops significantly once skeletal growth is complete.
• Risser sign (skeletal maturity): A specific X-ray measurement of the pelvis (the hip bone) used to estimate how much skeletal growth remains, graded from 0 (least mature, most growth remaining, highest risk of progression) to 5 (fully mature, growth complete). A low Risser sign at diagnosis is one of the strongest indicators that a curve may progress and require closer monitoring or bracing.
• Curve magnitude at diagnosis: Larger curves at the time of diagnosis are more likely to continue progressing than smaller ones, and progression tends to accelerate once a curve passes certain thresholds.
• Sex: Scoliosis is diagnosed more often in girls, and curves in girls are more likely to progress and require treatment than in boys.
• Timing relative to menstruation (in girls): Because rapid growth drives curve progression, a girl who is diagnosed before her first menstrual period generally has more growth — and therefore more time for potential progression — ahead of her than one diagnosed afterward.
• Younger age at diagnosis: Being diagnosed at a younger age generally means more growth remaining, and therefore a higher risk that the curve will progress before growth is complete.

Because of these factors, monitoring schedules are individualised — a small curve in a child with significant growth remaining may need X-rays every few months, while a stable curve close to skeletal maturity may only need occasional review.

Possible Complications of Scoliosis

The great majority of scoliosis cases are mild and do not cause significant complications, but if a curve becomes more severe, particularly if untreated, it can lead to the following.

• Breathing problems: In more severe curves, the ribcage and spine can compress the space available for the lungs, making it physically harder to breathe deeply, and in significant cases, affecting long-term lung development, particularly in early-onset scoliosis.
• Cardiac strain: In rare, very severe cases, significant chest wall deformity can place additional strain on the heart, though this is uncommon with modern monitoring and treatment.
• Chronic back pain: People who had scoliosis as a child, particularly with larger curves, are somewhat more likely to experience chronic back pain in adulthood compared with the general population.
• Visible changes to posture and body shape: As a curve worsens, visible changes such as uneven shoulders or hips, or a waist that shifts to one side, can become more pronounced, which can affect self-image and confidence, particularly in adolescents.
• Nerve compression: In degenerative scoliosis, the same changes that cause the curve can also narrow the space around spinal nerves, leading to sciatica-like leg pain, numbness or weakness.

How Scoliosis Is Diagnosed

Diagnosis combines physical examination with imaging to confirm the presence, type, severity and likely behaviour of a curve.

• Physical Examination: Includes visual assessment of shoulder, hip and waist symmetry, spinal alignment, and the Adam's forward bend test, along with a neurological examination to check for any signs suggesting an underlying neuromuscular cause.
• Standing X-Ray of the Whole Spine: The primary investigation used to confirm scoliosis and measure the Cobb angle, providing the objective baseline against which future change is measured. A pelvic X-ray view is also used to assess the Risser sign and estimate remaining skeletal growth.
• MRI Scan: Not required for typical, mild adolescent idiopathic scoliosis, but recommended in certain situations — such as atypical curve patterns, rapid progression, associated pain, or neurological symptoms — to look for an underlying cause such as a spinal cord abnormality.
• Pulmonary Function Tests: May be used in more severe curves, particularly those affecting the chest wall significantly, to assess how much the curve is affecting lung capacity and breathing function.
• Genetic and Underlying Condition Screening: Considered when congenital or neuromuscular scoliosis is suspected, to identify any associated conditions affecting other organ systems that may need coordinated care.

Living With Scoliosis: Practical Guidance

For those being monitored or treated for scoliosis, a few practical measures can support comfort, function and long-term spinal health alongside specialist care.

• Stay physically active: Regular physical activity, including core and back-strengthening exercises, supports general spinal health and function, and does not worsen scoliosis — inactivity is not protective and is generally discouraged.
• Follow brace-wear guidance closely: For adolescents prescribed a brace, wearing it for the recommended number of hours each day is the single most important factor in its effectiveness — inconsistent use significantly reduces its ability to prevent curve progression.
• Keep up with scheduled monitoring: Attending scheduled monitoring appointments, even when there is no pain or obvious change, is essential, since curve progression is identified through measurement over time rather than through symptoms.
• Support emotional wellbeing: Scoliosis, particularly during adolescence, can affect self-image and confidence; open conversations, peer support, and reassurance that most cases are very manageable can make a meaningful difference.
• Support bone health in adult-onset scoliosis: For adults with degenerative scoliosis, maintaining bone density through diet, appropriate exercise and, where relevant, osteoporosis treatment can help reduce the impact of further age-related spinal changes.