A spinal curvature of 10 degrees or more is considered scoliosis. Anything below 10 degrees is classified as normal spinal variation and does not receive a diagnosis. That 10-degree threshold is measured using a specific method called the Cobb angle, which your doctor calculates from a standing X-ray of your spine.
How the Cobb Angle Is Measured
The Cobb angle isn’t something you can estimate by looking in a mirror. It’s determined from a full-spine X-ray taken while you’re standing upright. A radiologist or orthopedic specialist identifies the two vertebrae that tilt the most at the top and bottom of the curve, draws lines along their edges, and measures the angle where those lines intersect. The resulting number, in degrees, is what determines whether you have scoliosis and how severe it is.
This measurement is the standard worldwide. A slight curve of 5 or 7 degrees might show up on an X-ray, but it falls within the range of normal spinal asymmetry and wouldn’t be called scoliosis.
Mild, Moderate, and Severe Ranges
Once a curve crosses that 10-degree line, it falls into one of three severity categories:
- Mild scoliosis: 10 to 24 degrees
- Moderate scoliosis: 25 to 39 degrees
- Severe scoliosis: 40 degrees or more
Most people diagnosed with scoliosis fall into the mild category. A curve in this range often causes no pain or visible asymmetry and may never need treatment beyond periodic monitoring. Moderate curves are where treatment decisions start to get more involved, and severe curves typically require more aggressive intervention.
What Each Severity Level Means for Treatment
The degree of your curve largely dictates the treatment path. For mild scoliosis (10 to 24 degrees), the standard approach is observation. Your doctor will schedule follow-up X-rays every 4 to 12 months, depending on your age and growth potential, to see whether the curve is stable or progressing. Many mild curves never worsen.
Bracing becomes the primary tool for moderate scoliosis, specifically curves between 25 and 40 degrees in children and adolescents who are still growing. The brace doesn’t straighten the spine. Its job is to prevent the curve from getting worse during the remaining growth years. Bracing is typically worn for a set number of hours per day, and compliance matters significantly for outcomes.
Surgery is generally recommended when curves exceed 45 to 50 degrees, or when a curve is progressing rapidly toward that range in a patient who is still growing. The most common procedure is spinal fusion, which corrects a portion of the curvature and stabilizes the spine with rods and screws so the curve can’t worsen further. The Scoliosis Research Society notes that surgery is also considered for patients whose curves continue progressing past 45 degrees even after growth has stopped.
Why the Same Degree Can Mean Different Things
A 25-degree curve doesn’t carry the same urgency in a 15-year-old girl as it does in a 30-year-old man. The biggest factor influencing what a given Cobb angle means for your future is how much growing you have left to do. Scoliosis curves tend to worsen during growth spurts, so a moderate curve in a young adolescent with years of growth ahead is a bigger concern than the same curve in someone whose skeleton has matured.
Doctors assess skeletal maturity using a grading system called the Risser scale, which looks at how much of the pelvic bone’s growth plate has hardened. A Risser grade of 0 means significant growth remains, while higher grades indicate the skeleton is nearing or has reached full maturity. Prediction models combine the Risser grade with the patient’s age, sex, and current Cobb angle to estimate the likelihood that a curve will progress to 45 degrees or beyond without treatment.
Girls face a higher progression risk than boys, partly because their growth spurts tend to be more dramatic and partly because scoliosis is diagnosed in girls at a much higher rate. A 12-year-old girl with a Risser 0 grade and a 30-degree curve has a substantially different outlook than a 15-year-old boy with the same measurement and a Risser grade of 2 or higher.
Curves in Adults
In adults, scoliosis curves are generally stable because growth has stopped. A mild or moderate curve that hasn’t changed in years typically needs no treatment. The concern shifts from progression to symptoms: pain, stiffness, or in severe cases, compression of the lungs or other organs. Degenerative scoliosis, which develops later in life as spinal discs and joints wear down, can also cause new curvature in people who had straight spines as teenagers.
For adults, treatment decisions are driven more by symptoms and quality of life than by the degree number alone. An adult with a 50-degree curve and no pain may need nothing more than exercise and periodic check-ins, while someone with a 35-degree curve causing nerve compression and significant daily pain might be a candidate for surgical correction.