This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Disorder of Metabolism & Connective Tissue, Subject name: Medicine
Joint not involved in Rheumatoid arthritis? 
Select and explain. 
A. D.I.P, B. P.I.P, C. M.C.P, D. Wrist
A: D.I.P
Answer: A: D.I.P 
Explanation: Ans.(a) D.I.PRef : Harrison 19th ed. / 2142* Rheumatoid arthritis characteristically causes swelling of small joints in the hand like the P.I.P, M.C.P and the wrist joint bilaterally.* Isolated D.I.P joint involvement is seen in psoriatic arthropathy.* D.I.P joint involvement is also seen with osteo-arthritis but the involvement is with pain at the base of thumb. Knee joint is the commonest joint involved in these patients.