Dynamic X-rays show movement in the spine. These can be done while bending forward then again while bending backward. Some are compared from sitting to standing. The idea is to see how much the bones move, tilt, slip, or slide during motion. Too much movement can mean the spine is unstable.
There are new MRI scanners now that can measure spinal movement while bending forward, back, and sideways. Sit-to-stand views can also be taken. Looking at the limits of spinal motion helps the doctor find areas where abnormal motion exists. Pinpointing the problem can help direct treatment more specifically.