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
[{'content': 'Swan neck deformity - \nSelect and explain. \nA. Flexion at PIP and DIP joint, B. Extention at PIP and DIP joint, C. Flexion at PIP and Extention at DIP joint, D. Extention at PIP and Flexion at DIP joint', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. is 'd' i.e., Extention at PIP and Flexion at DIP joint * Boutonniere deformity: Flexion contracture of PIP joint and extension of DIP joint.* Swan neck deformity: Hyperextension of PIP joint and flexion at DIP joint.", 'role': 'assistant'}]