SPONDYLOLYSIS AND SPONDYLOLISTIES
These linked conditions generally affect your lower back but may occur in may part of your spine.Spondylolysis occurs when a defect or weakness in a vertebrae develops into a fracture. The vertebra is then at risk of slipping out of line with the vertebrae adjacent to it, leading to spondylolosthesis, which can be debilitating and painful, or may be painless and go unnoticed.

CAUSES
Spondylolysis may start with a minor crack the narrow arch of bone in a vertebra,known as the usually it is the result of a fall or due to strain and overuse .some sports such as cricket and soccer repeatedly put stress on the arches of the vertebrae ,which can lead to minor cracks or breaks.Spondylolisthesis generally develops from spondylolysis ,with the crack widening to a complete break due to further stresses and strains .This break allows the damaged vertebra to slip out of line, which can irritate the linked facet joints and ligaments and possibly trap a nerve.

SYMPTOMS AND DIAGNOSIS
The pain from a displaced vertebra due to spondylolisthesis depends on the degree of slippage. A slight slip may cause little or no pain, while a greater degree of slippage can lead to more intense pain because of the irritation to the spinal joints and ligaments .If your nerve is trapped, there may be some pain numbness, or “pins and needless” in one or both of your legs. Your doctor will make a diagnosis through a physical examination and testing including on X-ray, MRI scan and myelogram.

RISKS AND RECOVERY
Back strengthening exercises can help stabilize your posture, but where vertebrae have severely slipped, nerve entrapment can develop that may require surgery. Young people diagnosed with spondylolisthesis should avoid contact sports and activities with a high risk of back injury .A young person who is still growing should be monitored every six months, using X-rays to detect further movements and shift in the spinal column. Once growth stops, the vertebrae are unlikely to slip any farther.