Lumbar instability is a condition in which the lumbar spine segments of motion exceed their limits and exhibit abnormal responses under normal physiological loads, that is, the range of motion of the segments of motion under a given load is increased or abnormal due to decreased stability of the functional units of the spine. The risk of low back pain, progressive deformity and compression of neural structures arises. Lumbar instability is a major cause of chronic low back pain, postoperative lumbar spine syndrome and sciatica, and is due to the inability of the lumbar intervertebral joints to maintain their physiology under normal loading, abnormal motion and the resulting range of clinical symptoms. Degenerative lumbar spondylolisthesis is due to long lasting instability of the lumbar spine, causing degenerative changes in the corresponding small joints, and the joint protrusion becomes horizontal, coupled with the degeneration of the intervertebral disc, making the connection between the vertebrae loose and unstable, and gradually occurring lumbar spondylolisthesis. This disorder is also called pseudoslip because the isthmus remains intact. Mostly seen after the age of 50, more women than men, mostly occurring in the lumbar 4 vertebrae forward slip, followed by the lumbar 5 vertebrae forward slip. The degree of degenerative lumbar spine slippage is generally mild, mostly within 2 degrees of slippage.