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
In ankylosing spondylitis, radiological change are first seen in - 
Select and explain. 
A. Sacro-iliac joints, B. Intervertebral ligament, C. Vertebral bodies, D. Intervertebral discs
A: Sacro-iliac joints
Answer: A: Sacro-iliac joints 
Explanation: None