It's hard to tell if you have spondylolisthesis because you may not have any symptoms or overwhelming pain—most people don't. Spondylolisthesis is usually discovered when you're being tested for something else and the doctor notices the slipped vertebra on an x-ray.
X-rays are the best way to diagnose spondylolisthesis. During the x-ray, you'll probably stand facing the side—that's so the doctor can get a lateral (side) view, which most clearly shows the slip. Looking at the lateral x-ray below, you can see that one of the vertebra has slipped off the spinal column. The arrow points to the spondylolisthesis.
Your doctor may also order an oblique x-ray. Oblique means that the x-ray is taken at an angle from the back, a view that will help the doctor see the lamina, facet joints, and pars interarticularis.
To see if your spondylolisthesis is unstable and moving, the doctor may perform flexion and extension views from the side. These are also called lateral bending views. A flexion x-ray is taken with you bending forward; an extension x-ray is taken with you bending backwards.
For further confirmation of spondylolisthesis, you may need to have a CT scan.
If the slipped vertebra is pressing on nerves, the doctor may order a myelogram. In this test, you'll have a special dye injected into the area around your nerves—your nerves are in a sac, so the dye will go into that sac. (Before that happens, the area will be numbed.) Then you'll have an x-ray or a CT scan. The image will provide a detailed anatomic picture of your spine, especially of the bones, that will help your doctor to identify any abnormalities.
Part of your visit to the doctor will include physical and neurological exams. In the physical exam, your doctor will observe your posture, range of motion (how well and how far you can move certain joints), and physical condition, noting any movement that causes you pain. Your doctor will feel your spine, note its curvature and alignment, and feel for muscle spasms. Spondylolisthesis can cause you to walk abnormally, so the doctor may need to watch you walk.
During the neurological exam, your spine specialist will test your reflexes, muscle strength, other nerve changes, and pain spread (that is—does your pain travel from your back and into other parts of your body?). The physical and neurological exams will give your doctor a good picture of how the slipped vertebra is affecting your body and life.
Using the lateral (side) x-ray, your doctor will grade your spondylolisthesis. He or she will use a grade I through grade V scale that describes how far forward your vertebra has slipped.