Spondylolisthesis is perhaps the worst disorder of the lumbar spine. Two-five percent of all people are born with a defect (spondylolysis) in the most important strut in the low back at the last lumbar vertebrae. 50% of these people will fracture that defect during their life and develop symptomatic spondylolisthesis. This fracture results in the last lumbar vertebrae sliding forward on the sacrum causing the spinal cord to be crushed. Surgery has a high failure rate because of the massive forces of gravity acting on the surgical site. This disorder is diagnosed by taking oblique (45 degree angle) x-rays of the back from both sides. Sacroiliac instability is the most probable cause of pain in patients who have normal x-rays. These patients eventually seek out chiropractors after their family doctor and orthopedist fail to make the diagnosis.