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 be involved in osteoahritis 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: Answer is D (Metacarphalangeal joints) Wrists and Metacarpophalangeal joints are generally not involved in Osteoahritis - Harrison 16th/2040 Sparing of wrist and metacarpophalangeal joint with involvement of base of thumb (i.e. carpometacarpal joint) is very characteristic of 'osteoahritis'.