This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology and Rheumatology, Subject name: Medicine
Heberdens nodes are the clinical manifestations seen in - 
Select and explain. 
A. Osteoarthritis, B. Rheumatoid arthritis, C. Ankylosing spondylitis, D. Reactive arthritis
A: Osteoarthritis
Answer: A: Osteoarthritis 
Explanation: Ans. is 'a' i.e., Osteoarthritis Joints involved in Osteoarthritis* OA affects certain joints, yet spares others.* Commonly affected joint include Hip, knee, cervical & lumbosacral spine, and first metatarsophalangeal joint. In Hands, the distal interphalangeal joints (DIP), proximal interphalangeal joints (PIP) and first carpo metacarpal joint (base of thumb) are involved while sparing metacarpophalangeal (MCP) joints. Shoulder joint may be affected but uncommonly.* Usually spared joints are the wrist, elbow, metacarpophlangealand ankle. This may simply reflect the fact that some joints are more prone to predisposing abnormalities than others.In osteoarthritis of handi) Distalinterphalangeal jointHeberderis node.ii) Proximalinterphalangeal jointBouchard's node