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: Medicine
Least common site to involved in osteoarthritis amongst the following is - 
Select and explain. 
A. Hip joint, B. Knee joint, C. Carpometacarpal joint of thumb, D. Metacarpophalangeal joint
D: Metacarpophalangeal joint
Answer: D: Metacarpophalangeal joint 
Explanation: None