scoliosis
Meaning of scoliosis: The twist counts as much as the bend, since rotation pushes the ribs into the hump that reveals a curve on bending forward.
Definition of scoliosis
Scoliosis is a sideways curvature of the spine combined with rotation of the vertebrae, so the backbone bends into a C or an S shape and the ribs are twisted along with it. Small curves are common and cause nothing at all. Larger ones show as uneven shoulders, a prominent shoulder blade, or a rib hump appearing when the person bends forward.
What causes the curve?
| Type | Cause | Typical onset |
|---|---|---|
| Idiopathic | No identified cause | Mostly adolescence |
| Congenital | Vertebrae malformed before birth | Present from birth |
| Neuromuscular | Weak or unbalanced trunk muscles | Childhood, with the underlying disorder |
| Syndromic | Disorders of collagen and connective tissue | Variable |
| Degenerative | Wear of the discs and facet joints | Later adult life |
The idiopathic form accounts for the large majority. It clusters within families, affects girls more often once curves reach a size that matters clinically, and has no established cause despite long investigation.
Why does the twist matter as much as the bend?
Scoliosis is a three-dimensional deformity rather than a simple sideways lean. Each vertebra rotates on the one below as the spinal column curves, and because the ribs are fixed to the vertebrae they turn with them. On one side the ribs are pushed backward, raising a hump, and on the other they flatten. That is why a curve barely visible when a person stands upright becomes obvious on bending forward, when the rib prominence stands proud. Rotation also explains why a curve can look smaller in a photograph than it measures on an X-ray.
Does posture or a heavy bag cause it?
No. Carrying a bag on one shoulder, slouching, sleeping position and sport do not produce scoliosis, and correcting any of them does not reverse one. What does govern the course is growth. A curve appearing before the adolescent growth spurt has years of rapid growth still to run and more opportunity to increase, while one found near skeletal maturity changes little afterward. Curves in adults follow a different logic, progressing slowly through disc degeneration and vertebral collapse, and osteoporosis contributes to that. Very large curves reduce the space available to the lungs, which is why chest expansion is assessed alongside the angle.
Also known as
Used in a sentence
Screening detected a mild thoracic scoliosis with a right sided rib prominence.
Good to know
Posture, heavy bags and sleeping position do not cause scoliosis, and most adolescent curves have no identifiable cause. A curve appearing before the growth spurt has more remaining growth over which to increase than one found near skeletal maturity.
Word origin
Where “scoliosis” comes from
From the Greek skoliosis, a bending, from skolios, meaning crooked or curved.