The one-sentence version
Viewed from behind, a healthy spine runs straight; with scoliosis, it curves sideways — often with a slight rotation of the vertebrae — most often in the mid-back (thoracic) or lower back (lumbar), and usually in a single long “C” or a double “S” pattern.
The main types
| Type | Typical age | What it means |
|---|---|---|
| Adolescent idiopathic (AIS) | 10–18 | The most common form (~80% of cases). “Idiopathic” = no known single cause; genetics play a role. Most AIS curves are mild and never need more than monitoring. |
| Adult degenerative (“de novo”) | 50+ | Develops later in life as discs and joints wear unevenly. Very common — one study found thoracic scoliosis in about a quarter of people over 50, usually mild (10°–20°) [1]. |
| Adult progression of AIS | 30+ | Childhood curves that persist or slowly worsen into adulthood, sometimes accelerating after menopause. |
| Functional (non-structural) | Any | The curve comes from something outside the spine — commonly a leg-length difference or muscle guarding — and often improves when the cause is addressed. |
| Congenital / neuromuscular / syndromic | Birth–childhood | Rarer forms from vertebrae forming abnormally, or conditions like cerebral palsy or muscular dystrophy. Managed by specialist teams. |
How common is it?
- About 2–3% of the US population — roughly 6–9 million people — has scoliosis.
- Only a small fraction of those curves ever need treatment: most are mild and simply observed.
- In older adults the numbers rise sharply: degenerative curves become common from the 50s onward [1] — scoliosis is not just a teenage condition.
The Cobb angle, in one paragraph
On a standing X-ray, the radiologist tilts the most-tilted vertebra at the top of the curve and the most-tilted one at the bottom; the angle where those two lines cross is the Cobb angle. It's the universal yardstick: 10°+ = scoliosis; ~10–25° is mild (usually monitor every 4–6 months in growing teens); ~25–45° moderate (bracing may be discussed in growing teens; exercise therapy often prescribed); 45–50°+ severe (surgery may be discussed, mainly when progressing or painful). Two doctors measuring the same film can differ by a few degrees — that's normal, and one reason a single number shouldn't drive panic.
When to see a doctor promptly
- New or worsening numbness, tingling, or weakness in legs or arms
- Difficulty breathing or chest tightness linked to your spine
- Rapidly visible curve change, rib hump growth, or clothes fitting unevenly
- Back pain that wakes you at night, or with fever/unexplained weight loss
- Any curve discovered during growth spurts (get a baseline X-ray)
For stable mild curves in adults, the usual path is periodic monitoring, exercise, and pain management — not surgery.
Where to go next
- Exercises & what the evidence supports →
- Dead hangs & scoliosis: the evidence review →
- Dead hang time calculator →
References
- Urrutia J, et al. (2014). Thoracic scoliosis prevalence in patients 50 years or older. PubMed 24153170
- Overview & statistics: scoliosis epidemiology on PubMed