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: Orthopaedics
[{'content': 'Swan-neck deformity is - \nSelect and explain. \nA. Flexion of Metacarpophalangeal joint and extension at interphalangeal joint, B. Extension at Proximal interphalangeal joint and flexion at Distal interphalangeal joint, C. Flexion at proximal interphalangeal joint and extension at distal interphalangeal joint, D. Extension at Metacarpophalangeal joint and flexion at interphalangeal joint', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Important hand deformities of hand in RA\n\nBoutonniere deformity: Flexion contracture of PIP joint and extension of the DIP joint.\nSwan neck deformity: Hyperextension of PIP joint and flexion at DIP joint.\nZ-deformity: Radial deviation of the wrist with ulnar deviation of fingers.\nHyperextension of 1st interphalangeal joint and flexion of MP joint.', 'role': 'assistant'}]