This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Arthritis, Subject name: Orthopaedics
Bamboo spine appearance is seen in - 
Select and explain. 
A. Ankylosing spondylitis, B. Rheumatoid arthritis, C. Osteoarthritis, D. DISH
A: Ankylosing spondylitis
Answer: A: Ankylosing spondylitis 
Explanation: Ans. is 'a' i.e., Ankylosing spondylitis Radiological features of ankylosing spondylitis* Radiographic evidence of sacroiliac joint is the most consistent finding in ankylosing spondylitis and is crucial for diagnosis. The findings are -i) Sclerosis of the articulating surfaces of SI jointsii) Widening of the sacroiliac joint spaceiii) Bony ankylosis of the sacroiliac jointsiv) Calcification of the sacroiliac ligament and sacro-tuberous ligamentsv) Evidence of enthesopathy - calcification at the attachment of the muscles, tendons and ligaments, particularly around the pelvis and around the heel.* X-ray of lumbar spine may showi) Squaring of vertebrae : The normal anterior concavity of the vertebral body is lost because of calcification of the anterior longitudinal ligament.ii) Loss of the lumbar lordosis.iii) Bridging 'osteophytes' (syndesmophytes)iv) Bamboo spine appearance