This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Joint Disorders, 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: Boutonniere deformity involves: Flexion at PIP and extention at DIP joint seen in RA Other deformities in RA- Swan-neck deformity Z-deformity of thumb Ulnar detion of fingers