Sacralization of the fifth lumbar vertebra (or sacralization) is a congenital anomaly, as the transverse process of the last lumbar vertebra (L5) becomes larger than normal on one side or both sides, and fuses to the sacrum, or ilium, and or both. These anomalies are observed at about 3.5 percent of people, and is usually bilateral. Although, sacralization may be as one of causes of low back pain, but is asymptomatic in many cases (specially bilateral type). Probably, low back pain occurs due to chronic faulty biomechanics. In sacralization, usually L5-S1 intervertebral disc becomes thin and narrow. This abnormality is found by X-ray.