Degenerative spondylolisthesis

What it is

As the disc and facet joints at a level wear, they can stop holding the two vertebrae in line, and one drifts forward on the other. This most often happens at L4–L5 and is more common in women over sixty.

The slip itself is frequently painless. What causes symptoms is the canal narrowing that comes with it, and sometimes movement at the unstable level.

What it feels like

• Leg symptoms typical of stenosis — cramping and heaviness on walking, eased by sitting.
• Back pain that is worse on standing or changing position, and better lying down.
• A sense of the back "giving way" or needing frequent rests.

How it is assessed

Standing X-rays are important here, because a slip can reduce when you lie down for an MRI and so look less significant than it is. Flexion and extension views show whether the level actually moves.

MRI shows the nerve compression and the state of the discs and joints.

Treatment

Non-operative care is the starting point and works well for many people: physiotherapy focused on core and hip strength, activity modification, and injections where a flare needs settling.

Where surgery is needed, the question is whether decompression alone is enough or whether the level should also be stabilised. A slip that moves on flexion and extension views, or significant mechanical back pain, points towards adding a fusion. A stable slip with purely leg symptoms may need only a decompression.