This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Joint disorders, Subject name: Orthopaedics
[{'content': 'Subluxation of atlanto-occipital joint is seen in all except: \nSelect and explain. \nA. Gout, B. Odontoid dysgenesis, C. Rheumatoid ahritis, D. Ankylosing spondylitis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Gout very rarely causes cranioveebral anomalies CRANIOVEEBRAL (CV) JUNCTION ANOMALIES: Subluxation of BASE OF SKULL + C1 + C2 Causes are: *', 'role': 'assistant'}]