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
Boutonniere deformity involves - 
Select and explain. 
A. 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
C: Flexion at PIP and Extention at DIP joint
Answer: C: Flexion at PIP and Extention at DIP joint 
Explanation: Ans. is 'c' i.e., Flexion at PIP and Extention at DIP joint Important hand deformities of hand in RA* Boutonniere deformity: Flexion contracture of PIP joint and extension of DIP joint.* Swan neck deformity: Hyperextension of PIP joint and flexion at DIP joint.* Z-deformity: Radial deviation of wrist with ulnar deviation of fingers.* Hyperextension of 1st interphalangeal joint and flexion of MP joint.