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
Swan neck deformity is seen in ? 
Select and explain. 
A. Osteoahritis, B. Rheumatoid ahritis, C. Psoriatic ahritis, D. Gout
B: Rheumatoid ahritis
Answer: B: Rheumatoid ahritis 
Explanation: Ans. is b' i.e., Rheumatoid ahritis Impoant deformities of hand in RA Boutonniere deformity : Flexion contracture of PIP joint and extension of DIP joint. Swan neck deformit: Hyperextension of PIP joint and flexion at DIP joint. Z-deformity : Radial detion of wrist with ulnar detion of fingers. Hyperextension of 1st interphalangeal joint and flexion of MP joint.