Spondylolysis refers to a defect in one of the bones of the spine. The vertebrae of the low back are affected most often. Spondylolysis is not something we are borne with. It may be a stress fracture that never completely healed.
In the early stages of spondylolysis there's a chance that the bone will heal on its own. Wearing a brace or corset keeps the spine from moving and allows it to form a solid line of bone. Immobilizing the spine can also decrease painful symptoms. Sports activity is restricted because of the risk of trauma. Repetitive motions are also a risk factor for increasing the load on the spine.
If the bone doesn't form a solid union, then surgery may be required. Left untreated the condition can get worse and progress to spondylolisthesis. In spondylolisthesis the body of the vertebrae slips forward over the vertebrae below it. This can put pressure on the spinal nerves and causes instability of the spine.
Follow your doctor's advice for the full six months for the best results.