View Full Version : Help with terminology, please

06-08-2005, 03:13 PM
Can anyone tell me what a "Cobb" angle is??? How about a "Risser sign?"

I assume they are both named after physicians, but what exactly do they measure?

Thanks, just want to be able to talk the talk!

Lia's Mom

06-08-2005, 03:31 PM
Hi Lia's mom...

Risser sign is an approximate measurement of the amount of growth left in an individual. Here's one of the way it's calculated:


Cobb angle is a measurement of the severity of scoliosis curves. You can see how it's calculated here:



06-08-2005, 03:32 PM

Cobb Angle is the measurement used to describe the degree of lateral (side-to-side) curvature in the spine. Imagine you are looking at an x-ray of the scoli person's back. To compute the Cobb Angle, you draw a line across the top of the highest vertebra in the curve, and a line across the top of the lowest vertebra in the curve. You extend those two lines out until they cross. You then measure the angle of the two lines at the intersection. (Actually it's the angle of two lines perpindicular to the intersection, but the concept is the same). In a normal spine, any two lines you made like this would be flat, so they would extend forever and never intersect. If there was a slight curve, the two lines would tilt slightly in toward each other, and eventually they would cross. The greater the curve, the more extreme the tilt of the lines, and the higher the Cobb Angle measure. This web page has a good diagram of how the measurement is done:


The Risser sign is a measure of skeletal maturity. It ranges from 0 for a pre-pubescent child, to 5 for a completely mature adult. Super accurate measurement of the Risser is done from an x-ray by examining how fully fused the bones of the pelvis are (this fusion completes at maturity), but can be estimated by various signs such as the starting of periods in girls, development of body hair, etc. Risser is important in scoli, because, in most cases, moderate curves will only continue to progress until skeletal maturity is reached. If your child is Risser 4, she's nearly done growing, so there's not so much to worry about. If your child is Risser 0 and already has a significant curve, there's so much growing left that the odds of the curve becoming large enough to require treatment are higher. My daughter was diagnosed with curves of 37 and 30 at Risser 0. We knew we were in trouble.....

Cheers - Patricia