Spondylolisthesis is diagnosed as an anterior slippage and inability to resist shear forces of a vertebral segment in relation to the vertebral segment immediately below it.
It most commonly occurs in the lumbar spine in the L5-S1 segment.
The most serious result of this spinal instability and the inability of the spine to maintain its normal position and posture when placed under a load.
Spondy is graded based on the percentage of the slip.