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: Orthopaedics
Ostearthritis commonly involves -a) Proximal IP jointb) Distal IP jointc) Ist carpometacarpal jointd) Wrist jointe) Distal radio - ulnar joint 
Select and explain. 
A. abc, B. bc, C. acd, D. bcd
A: abc
Answer: A: abc 
Explanation: Joint involvement in OA

Common joints : Knee, Hip, Spine (cervical, lumbosacral), Hand (PIP, DIP, first carpometacarpal), first tarso-metatarsal.
Uncommon joint : Shoulder
Spared : Wrist, elbow, ankle, metacarpophalangeal.