Your "back bone" is actually a series of 24 vertebrae (vertebral bones ) that move together and are connected to one another by the discs of the back and the facet joints. The discs and facet joints have three functions: to help connect one spinal bone o to the other, allow for movement of the spine, and to protect the bones by provide for a slick surface that reduces friction. Spondylolysis is a condition where the facet joints degenerate or wear down to the point where the vertebrae detach from one another. The result of this breakdown of the facet joints may be pain or instability of the spine. Spondylolysis causes the vertebrae to become unstable and even loose because it is cracked. If the affected vertebrae move out of alignment, the result is a condition of a similar name - Spondylolisthesis. The result of Spondylolysis may be back pain or neck pain because of pressure on the nerves as they exit the spine.
Spondylolysis occurs across the back of the vertebrae. This degenerative process may begin as a crack, or hairline fracture. This condition may be seen on an X-Ray. It is surprisingly common, and it may or may not be the cause of your back pain. Estimates are that about 5% of the population have this condition. Spondylolysis may present in any section of the vertebral column, though the condition is most commonly documented for the lumbar vertebrae (particularly L5).
Back specialists think the cause of Spondylolysis may be a combination of genetic predisposition that causes a weakness of the vertebral bones and a lifestyle that puts a lot of stress on the spine. A person may have a predisposition to this condition, and have it present after an injury causes a stress fracture to the bone. It may affect people in younger age groups, especially people participating regularly in high impact or collision sports. Sports participation that may put youths and young adults at a greater risk for this condition include football, gymnastics, martial arts, diving, and tennis. Lineman in American football are particularly prone to this condition, because of the amount of bending and squatting and exploding out of the crouch position they have to do. In sports injuries that involve a lot of explosive movements out of a crouched position, the pars interarticularis may be especially vulnerable. The pars interarticularis is the part of the vertebra located between the inferior and superior articular processes of the facet joint. The explosive movements, such as a football lineman leaping out of a crouched position, can suddenly push two vertebrae together at the articulating processes, wearing down the facet joint(s) and possibly creating a hairline fracture that begins to widen over time.
The cracks that occur at the back of the vertebrae as a result of injury may heal on their own, and they may fail to heal. The condition may vary, in both the amount of structural damage present as the result of injury degenerative processes, and the severity of symptoms, as reported by the patient. Generally, mild spondylolysis causes neither mechanical problems or back pain, the structure of the affected vertebral bones remains intact, and the stability of the vertebral column is maintained. However, in rare instances, the initial hairline crack will widen. When this happens the condition is called spondylolisthesis, which can cause a serious back problem that must be treated or fixed.