How rare is a cynovial syst adjacent to facet at l2-l3?

Rare: The presence of a symptomatic synovial cyst next to the facet joint at l2-3 is unusual - according to this article, only 160 cases have been reported in the literature (j neurol neurosurg psychiatry 2001;70:74-77). However, such cysts are seen more often on ct or MRI of the spine, (often without symyptoms).

Not infrequent: These can be incidental findings on a ct or MRI image or they can create symptoms if they compress a nerve or the thecal sac they are a result of degrnerative changes in the facet joint usually.

Not that Rare: Synovial Cysts is an out pouching of the joint capsule for the facet joint. Think of a balloon that is overfilled with water or air, it starts to stretch and grow into something different than a round object. The same occurs in the facet joint when fluid accumulates in the joint due to stress reaction, arthritis or injury. It can compress on nerves exiting or even causing pain in the back.