Spondylosis refers to degenerative changes in the spine such as bone spurs and degenerating intervertebral discs between the vertebrae. Spondylosis changes in the spine are frequently referred to as osteoarthritis. Spondylolisthesis is forward or backward displacement of the body of one vertebra in relation to an adjacent vertebra. For example, anterior spondylolisthesis of L4 on L5 means that the fourth lumbar vertebra has slipped forward on the fifth lumbar vertebra.
As a result, the spine is not normally aligned. If the displaced vertebrae shift with the movement of the spine, this is referred to as dynamic spondylolisthesis. Dynamic shifting of the vertebrae is visualized with X-rays of the spine performed with patients flexing (bending forward) and then extending (bending backward) their back. Spondylosis deformans is the growth of bone spurs (osteophytes) or bony bridges around a degenerating intervertebral disc in the spine.