School screenings are the most common way to identify asymmetry that may need further screening. When in forward bend (Adam's test), a tool called a scoliometer can be used to detect a rotation. If greater than 5 degrees, you may have a positive screening. Other things you may notice is one shoulder consistently higher than another or a more prominent ribcage on one side of the spine.
This is not a diagnosis at this point. It flags the need for further testing. True diagnosis is based on an x-ray. If you have a positive screen, but no spinal rotation or lateral deviation on X-ray, there may be muscle asymmetry (imbalance)or joint restriction that is contributing to the functional scoliosis. Typically 10 degrees lateral deviation on x-ray (cobb angle) is what defines scoliosis as a diagnosis.
This is where a mild curve is often left to wait to see if it becomes more severe....THAT IS A PROBLEM! This is the time to intervene with scoliosis specific PT! This is the ideal time to learn positioning that will reduce risk of progression.