Lumbar juxta-facet cyst after trauma.

We report a post-traumatic lumbar facet cyst in which results of magnetic resonance imaging (MRI) performed at the time of injury were available. The patient was a 59-year-old man who presented with severe low back and right leg pain immediately after injury of his sacroiliac region in a traffic accident. MRI at the time of injury revealed high intensity signal change in the right facet joint at L4/5. Re-examination 5 months after the injury with MRI revealed a cyst, which was continuous with the facet joint. Surgical resection of the cyst yielded satisfactory results.