Overview
Spondylolisthesis is a condition in which one bone in your back (vertebra) slides forward over the bone below it. It most often occurs in the lower spine. In some cases, this may lead to your spinal cord or nerve roots being squeezed.
Causes
Congenital joint defect
Accident or trauma
Stress fracture
Infection or arthritis
Symptoms
Back or buttock pain that may run from the lower back down one or both legs
Numbness or weakness in one or both legs
Difficulty walking
Loss of bladder or bowel control
Leg, back, or buttock pain that gets worse with bending or twisting
Can be asymptomatic
Diagnosis
Physical examination
X-rays
CT scan
MRI
Treatment
Stopping of any activity that may have led to vertebrae damage
Anti-inflammatory and pain relieving drugs
Physical therapy
Weight loss in overweight people
Surgery
Source: http://www.emedicinehealth.com/spondylolisthesis-health/article_em.htm