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: Surgery
The posture associated with the greatest lumbar intradiscal pressure is 
Select and explain. 
A. Sitting, trunk flexed, B. Sitting, trunk erect, C. Standing, trunk flexed, D. Standing, trunk erect
A: Sitting, trunk flexed
Answer: A: Sitting, trunk flexed 
Explanation: Nachemson's studies showed the lowest intradiskal pressure occurred with the patient supine, followed by the lateral decubitus position. Sitting produced higher intradiskal pressures than standing, and pressures were increased in both positions by flexion of the trunk. The highest pressures encountered were with the patient sitting with the trunk flexed.