"Spondyl(o)" refers to the backbone or vertebra, and "olisthesis" means slipping. Spondylolisthesis is a slipping forward of one bone over another, mainly in the low back area. It is most often caused by a defect in the bony ring on the back of the spinal column. Some people develop the defect in the bone, but the vertebra never slips forward. Others may put extra stress on the bone and this causes slipping. This is especially likely when the activity or sport is combined with a rapid growth spurt.

Athletes with symptoms due to spondylolisthesis may be restricted from activities such as gymnastics that place high strain on the injured vertebra. Doctors sometimes place the athlete in a rigid brace or cast for three to four months.

Severe forward movement of the bone can put pressure on the spinal nerves. This can cause extreme back pain, nerve pain down the leg, and even changes in bowel and bladder function. If enough slipping occurs, and the condition isn't corrected with rest and bracing, surgery may be required.