The posterior ligamentous complex is injured in facet dislocations.  The affected superior facet displaces into the neural foramen, frequently (73%) causing radiculopathy. About half have associated facet fractures.

Facet dislocations are either unilateral or bilateral:  

• Unilateral facet dislocations are considered stable despite the ligamentous injury because the dislocated facet is ‘locked’.  About 12% still have associated spinal cord injury.
• Bilateral dislocations also involve injury to the anterior longitudinal ligament.  These are unstable, and approximately 87% have associated spinal cord injury.