Scoliosis is a sideways curve of the spine measuring at least 10 degrees on an X-ray. A healthy spine runs straight when viewed from behind, but a scoliotic spine bends into a C or S shape, and in most cases it also rotates, twisting the vertebrae so that the ribs or back muscles on one side stick out more than the other. About 2 to 3 percent of the population has some degree of scoliosis, and it affects roughly twice as many women as men overall.
Types and Causes
The most common form, idiopathic scoliosis, has no known cause. It typically appears during the growth spurt just before puberty, between ages 10 and 15. “Idiopathic” simply means doctors haven’t identified a specific trigger, though genetics clearly play a role since the condition runs in families. Among adolescents over age 10, idiopathic scoliosis occurs ten times more often in girls than in boys, and when it does appear in girls, the curve is up to eight times more likely to worsen compared to boys of the same age.
Less common types have identifiable origins. Congenital scoliosis develops before birth when vertebrae don’t form properly or fail to separate during fetal development. Neuromuscular scoliosis results from conditions that affect the muscles or nerves supporting the spine, such as cerebral palsy or muscular dystrophy. These curves tend to progress more aggressively because the muscles can’t stabilize the spine during growth.
Degenerative scoliosis is a separate category that develops in adults, usually after age 50, in a spine that was previously straight. It starts with age-related drying out of the spinal discs. When the discs and small joints of the spine wear down unevenly on the left and right sides, the spine gradually tilts under the body’s weight. Thickening of spinal ligaments and eventual instability of the vertebrae add to the problem over time.
How to Recognize It
Scoliosis often develops so gradually that neither the person nor their family notices it at first. The earliest visible signs are usually subtle asymmetries:
- Uneven shoulders, with one sitting higher than the other
- A shoulder blade that sticks out or appears larger on one side
- An uneven waistline, where the gap between the arm and the body differs from side to side
- One hip higher than the other
- The head not centered directly above the pelvis
- A constant lean to one side
Because the spine also twists as it curves, one side of the rib cage may push forward or a ridge of muscle may bulge on one side of the back. This is easiest to spot with the Adam’s Forward Bend Test, commonly used in school screenings: the person bends forward at the waist with feet together, knees straight, and arms dangling. In that position, any rib hump or unevenness along the back becomes much more obvious. A positive result doesn’t confirm scoliosis on its own but signals the need for an X-ray.
In adults with degenerative scoliosis, height loss and uneven pelvic alignment are common later signs.
When a Curve Gets Worse
Not every curve progresses. The biggest risk factor for worsening is how much growing the person has left to do. A 12-year-old with a 25-degree curve and years of growth ahead faces a much higher chance of progression than a 16-year-old with the same curve who is nearly done growing. Doctors gauge remaining growth using skeletal maturity markers, including a scale that tracks how much of the pelvic bone has hardened, to estimate how likely a curve is to reach the surgical threshold of 45 degrees before growth stops.
Larger curves at the time of diagnosis also carry more risk. A curve already at 30 degrees has more momentum to worsen than one at 15 degrees. Girls face higher progression risk than boys at every curve size, which is one reason screening is especially important for adolescent girls with a family history of scoliosis.
Once a person reaches skeletal maturity, mild and moderate curves generally stay stable. Curves above 45 to 50 degrees, however, tend to continue worsening slowly throughout adulthood, even after growth is complete.
Does Scoliosis Cause Pain?
In adolescents, mild to moderate scoliosis is usually painless. When teens with scoliosis do report back pain, it’s often unrelated to the curve itself and worth investigating for other causes. Adults are a different story. Degenerative scoliosis frequently causes back pain, leg pain, and stiffness because the same disc and joint breakdown driving the curve also compresses nearby nerves.
Severe curves, those exceeding roughly 70 degrees, can physically compress the chest cavity and reduce lung capacity. The effect depends not only on the angle but also on how many vertebrae are involved and where the curve sits along the spine. Curves higher in the back, near the ribcage, have more impact on breathing than curves in the lower spine. Below 70 degrees, lung function is rarely affected in any meaningful way in someone who doesn’t have another underlying condition.
How It’s Diagnosed
After a physical exam raises suspicion, the standard diagnostic tool is a standing X-ray of the full spine. A doctor measures the angle of the curve using a method called the Cobb angle: lines are drawn along the top and bottom vertebrae of the curve, and the angle between them determines severity. A measurement of 10 degrees or more confirms the diagnosis. Curves under 10 degrees are considered normal spinal variation.
For curves that may need treatment, or when doctors suspect an underlying cause like a spinal cord abnormality, an MRI can provide a more detailed look at the soft tissues around the spine.
Treatment by Severity
Treatment depends on the size of the curve, the risk of progression, and the person’s age.
Mild Curves (10 to 25 Degrees)
Most mild curves in growing children are simply monitored with periodic X-rays every four to six months. If the curve stays stable or the child finishes growing, no further intervention is needed. Physical therapy and targeted exercises can help with posture, core strength, and muscle balance, though they won’t reverse an existing curve.
Moderate Curves (25 to 45 Degrees)
For growing adolescents with curves in this range, bracing is the primary treatment. The brace doesn’t straighten the spine permanently. Its job is to hold the curve and prevent it from worsening during the remaining growth period. Effectiveness depends heavily on how many hours per day the brace is worn. Doctors typically prescribe anywhere from 6 to 18 hours of daily wear depending on the curve’s size and the child’s growth stage, and compliance makes a significant difference in outcomes. Once growth is complete, bracing stops.
Severe Curves (45 to 50 Degrees and Above)
Most scoliosis surgeons agree that curves reaching 45 to 50 degrees in a growing child will need surgery to prevent further progression. The standard procedure is spinal fusion, in which the curved vertebrae are realigned and fused together using metal rods, screws, and bone grafts. Over several months, the vertebrae grow together into a single solid section that can no longer curve. Curves between 40 and 50 degrees in a child still growing fall into a gray area where the decision depends on factors like how much growth remains and how fast the curve has been changing.
For adults, surgery is less about preventing progression and more about relieving pain or neurological symptoms that haven’t responded to non-surgical treatment. The decision is more complex in older adults because the surgery is major, recovery takes months, and the risks increase with age. Many adults with degenerative scoliosis manage their symptoms effectively with physical therapy, pain management, and activity modification without ever needing an operation.
Living With Scoliosis
The vast majority of people with scoliosis have mild curves that never require treatment beyond monitoring. For those who do need bracing or surgery, outcomes are generally good. Adolescents who wear their braces consistently have significantly lower rates of curve progression to the surgical range. Those who undergo spinal fusion typically return to most activities within several months, though the fused section of the spine will have permanently reduced flexibility.
Regular exercise, particularly activities that build core strength and improve flexibility like swimming and yoga, is beneficial at every severity level. Scoliosis does not prevent people from being physically active, playing sports, or having healthy pregnancies. The condition is lifelong, meaning periodic check-ins with a doctor remain useful even in adulthood, especially for curves that were moderate at the time growth stopped.