Hi Antoine,
I am no expert but I think what Cody was trying to say is the following:
If pain is experienced while you are simply sitting (no movement), it’s considered liver.
If pain is experienced when you are in the action of standing up from a seated position, then it’s something else. I think it would be considered Tai Yang as you are in the process of extending the body upright.
If you are standing and going into a seated position, then that’s considered body going into a flexion or coming together, which is Spleen or Taiyin (again, my understanding of it).
So, for simply being in a seated position with pain, numbness or any discomfort, you are looking at Liver.
Armin