This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
Pencil in cup deformity is seen in ? 
Select and explain. 
A. Rheumatoid ahritis, B. Ankylosing spondylitis, C. AVN, D. Psoriatic ahritis
D: Psoriatic ahritis
Answer: D: Psoriatic ahritis 
Explanation: Ans. is `4:1' i.e., Psoriatic ahritis Impoant