Wowk,
I was looking at the photo of your saddle again. There is something going on that is not right. I rode the same Brooks Pro for 30 years and tens of thousands of miles. Even after all that use, I did not put an indent in it that is even close to what you have after a couple thousand km. If something was going to dent a saddle it would be my bony butt. Granted, I took really good care of it and usually took it off in winter. One especially wet winter I took it off and replaced it with a new "winter" saddle. That Brooks never did go back on a bike I rode. I did put it back on the vintage Peugeot. I'm still riding those "winter" saddles. Everything is connected. Is the knee problem causing the saddle issues, or are saddle issues causing knee problems?
30 year-old, well used, Brooks Pro.