There is the true spondylolisthesis, created by a mechanical cause in a spondylolysis and the degenerative spondylolisthesis.
The latter is part of the pathology of the posterior vertebral joints.
True spondylolisthesis consists of a forward slipping of the spine at the fifth lumbar vertebra.
It is divided into 5 grades.
At the first grade we have forward slipping up to 25% of the body length of the first sacral vertebra, at the second grade up to 50%, at the third up to 75%, at the fourth up to 100% and at the fifth the spine has fully slid. Until the second grade it is usually asymptomatic or in some cases the patient feels mild aching in the waist which reflects in the buttocks after intense fatigue. After the third grade, symptoms depend on the extent of involvement of the nerve roots.
Treatment is usually conservative for the first grades of spondylolisthesis, with exercising of the deep lumbar stabilizers muscles, exercises to reduce lordosis and according the case, application of an anti-lordotic brace.
At advanced stages, treatment is clearly surgical with fusion of L5 and S1.