Anterior -posterior xrays of a long standing AIS patient.  From a supine to standing position, the right thoracic curve increased by 14 degrees.

Positive Bolster Sign - Right Photo

​Courtesy of:  UCSF  Dept Pharmacy and Medicine

Xrays for a patient with a spinal deformity should be taken with the patient standing.  The apparent deformity can be decreased by 10 degrees or more when the patient is supine (e.g., eliminating the impact gravity has on the spine).  This effect is most apparent when examining thoraco-lumbar and lumbar curves, particularly in girls with generalized ligamentous laxity.

A diagnosis of a structural scoliosis is made when the curve is greater than 10 degrees with concomitant rotation.

The key physical sign of a fixed structural scoliosis is a positive Forward Bend Test (See Figure below).  The ribs follow the spinal rotation - the prominence on the convex side is from the costal elements.  In the lumbar region, a positive Bolster Sign is noted (erector spinae muscles on the convex side are more  prominent)

Spinal X-Rays - Supine vs Standing