A scoliosis curve is named by combining three basic pieces of information: where in the spine the curve sits, which direction it bends, and how severe it is. A curve described as “moderate right thoracic scoliosis,” for example, tells you the curve is in the mid-back, bends to the right, and measures between 20 and 40 degrees. Understanding each piece of this naming system makes it much easier to read a radiology report or follow a conversation with a spine specialist.
Step One: Identify the Curve’s Location
Location is determined by the apex of the curve, the single vertebra (or disc space) that sits farthest from the midline of the spine. The Scoliosis Research Society defines specific boundaries for each region:
- Cervical: apex between C1 and the C6-C7 disc
- Cervicothoracic: apex at C7, T1, or the disc between them
- Thoracic: apex between T2 and the T11-T12 disc
- Thoracolumbar: apex at T12, L1, or the T12-L1 disc
- Lumbar: apex between the L1-L2 disc and the L4-L5 disc
- Lumbosacral: apex at L5 or below
Finding the apex is the single most important step because every other part of the name builds on it. On an X-ray, the apex is identified by looking for the vertebra with the greatest sideways distance from a vertical reference line drawn up from the center of the sacrum. In adolescents, most curves turn out to be thoracic. In adults, lumbar curves become more common because the lower spine is more vulnerable to age-related changes.
Step Two: Name the Direction
Direction refers to the side the curve bends toward, not the side the spine seems to lean away from. A curve that bows to the right is called dextroscoliosis. A curve that bows to the left is called levoscoliosis. On a standard front-facing X-ray, a right-sided (dextro) curve looks like a backward letter “C,” while a left-sided (levo) curve looks like a regular “C.”
Dextroscoliosis is more common in the thoracic spine, and levoscoliosis is more common in the lumbar spine. When a curve appears in an atypical direction for its region, such as a left-sided thoracic curve, clinicians may investigate further because atypical patterns are sometimes linked to an underlying cause like a spinal cord abnormality.
Step Three: Measure Severity With the Cobb Angle
Severity is expressed as a Cobb angle, measured in degrees on a standing X-ray. The measurement is taken between the most-tilted vertebra at the top of the curve and the most-tilted vertebra at the bottom. These are called the end vertebrae. The standard thresholds are straightforward:
- Under 10 degrees: considered a normal spinal variation, not scoliosis
- 10 to 20 degrees: mild scoliosis
- 20 to 40 degrees: moderate scoliosis
- Over 40 degrees: severe scoliosis
A curve must reach at least 10 degrees to be formally called scoliosis at all. This threshold matters because anything below it is classified simply as a “spinal curve” and typically requires no monitoring.
Putting the Name Together
Once you have location, direction, and severity, the full descriptive name reads naturally. A 15-degree curve bowing left with its apex at L3 would be called “mild left lumbar scoliosis” or “mild lumbar levoscoliosis.” A 45-degree curve bowing right with its apex at T8 would be “severe right thoracic scoliosis.” This descriptive format is what you will see most often in imaging reports and clinic notes.
Single Curves vs. Double Curves
Many people have more than one curve. A single curve creates a C-shaped appearance on X-ray. When two curves develop in opposite directions, the spine takes on an S-shape, and each curve gets its own name. One of these curves will have the largest Cobb angle and is called the major curve. Every other curve is a minor curve.
There is also an important distinction between structural and non-structural curves. A structural curve is rigid: it does not straighten out when you bend to the side. A non-structural curve (sometimes called compensatory) is flexible and corrects with bending. This distinction is tested with side-bending X-rays. If a curve’s Cobb angle corrects past zero degrees on a bending film, it is non-structural. Whether a curve is structural affects treatment decisions because structural curves are far less likely to improve on their own.
The Lenke Classification System
For adolescent idiopathic scoliosis, surgeons use the Lenke classification to plan treatment. It goes beyond the basic descriptive name and assigns a curve type from 1 through 6 based on which regions are involved and which curves are structural.
- Type 1: a single structural curve in the main thoracic region
- Type 2: two thoracic curves, both structural, with the main thoracic curve being larger
- Type 3: a structural thoracic curve paired with a structural lumbar curve (the thoracic is larger)
- Type 4: three structural curves in the upper thoracic, main thoracic, and lumbar regions
- Type 5: a single structural curve in the thoracolumbar or lumbar region
- Type 6: a structural thoracolumbar/lumbar curve paired with a structural thoracic curve (the lumbar is larger)
Each type also receives two modifiers. A lumbar modifier (A, B, or C) describes how far the lumbar apex sits from the center sacral vertical line. An “A” means the lumbar spine is well centered, while a “C” means the lumbar apex has shifted completely past the midline. A sagittal modifier captures how much forward rounding exists in the upper back, measured from T5 to T12: a minus sign means less than 10 degrees of kyphosis (a flat back), “N” means normal kyphosis of 10 to 40 degrees, and a plus sign means more than 40 degrees (excessive rounding). A complete Lenke designation looks something like “Lenke 1A-N.”
The Older King-Moe System
Before the Lenke system became standard, the King-Moe classification was widely used. It describes five patterns, all focused on thoracic and lumbar curves. Type 1 and Type 2 are both S-shaped double curves that cross the midline, distinguished by whether the lumbar curve (Type 1) or the thoracic curve (Type 2) is larger. Type 3 is a thoracic-only structural curve. Type 4 is a long C-shaped thoracic curve that extends low enough to tilt the fourth lumbar vertebra. Type 5 is a double thoracic curve. You may still encounter King-Moe types in older records, but most current surgical planning relies on the Lenke system because it captures more information about curve flexibility and the sagittal profile.
Kyphoscoliosis and Other Combined Names
Standard scoliosis naming describes a sideways curve when viewed from the front. But the spine also curves front-to-back, and when both planes are involved, the name changes. Kyphoscoliosis is used when scoliosis occurs alongside excessive forward rounding (kyphosis greater than 45 degrees in the upper back). Lordoscoliosis describes scoliosis combined with abnormal inward curvature. These combined names flag that treatment needs to address curvature in two planes, not just one.
Prefixes based on cause can also appear. Idiopathic scoliosis means no known cause, which accounts for the vast majority of cases. Congenital scoliosis results from vertebrae that formed abnormally before birth. Neuromuscular scoliosis develops because of a neurological or muscular condition affecting spinal support. These cause-based labels are added before the curve description, so a full name might read “congenital moderate left lumbar scoliosis.”