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
The joint commonly involved in sphffitic arthritis is- 
Select and explain. 
A. Hip, B. Shoulder, C. Wrist, D. Knee
D: Knee
Answer: D: Knee 
Explanation: Syphilic arthritis

Syphilic arthritis may be seen in congenital or acquired syphilis.

Congenital syphilis

The joint may be affected early or late : -


Early congenital syphilis : - Osteochondritis in juxta-epiphyseal region results in breakdown of the bone and cartilage.
Late congenital syphilis : - Painless synovitis at puberty is called clutton's joint. Most common site is knee followed by elbow, and often is bilateral.

Acquired syphilis

Joint may be involved in the secondary or tertiary stage.


Secondary stage : - Transient polyarthritis.
Tertiary stage : - Gummatous polyarthritis, Chorcot's (neuropathic) joint.