Spondylolisthesis is a spinal condition characterized by the forward displacement of one vertebra over the vertebra below it. This displacement can occur in any region of the spine but most commonly affects the lumbar (lower back) or cervical (neck) regions. Here’s a detailed description:

1. Types of Spondylolisthesis:

   • Isthmic Spondylolisthesis: This type is often due to a defect in the pars interarticularis, a small bony bridge that connects the facet joints in the spine.
   • Degenerative Spondylolisthesis: Occurs as a result of aging and wear-and-tear on the intervertebral discs and facet joints.
   • Traumatic Spondylolisthesis: Caused by a specific injury to the spine.
   • Pathological Spondylolisthesis: Resulting from an underlying condition such as a tumor or infection weakening the bones.

2. Grades of Severity:

   • Grade 1: Represents a mild slippage, typically less than 25% displacement.
   • Grade 2: Moderate slippage, usually between 25% and 50% displacement.