I have knee issues and thought I would try these stirrup turners. They were easy to put on and I was able to find my off stirrup very easily when I mounted.
However, I ride in paddock boots and capris most of the time in the summer and the edge of them rubbed me right above my boot. When I wore jeans and regular boots, it wasn't an issue.
My knees didn't bother me while I rode, but the rubbing well, it rubbed me raw. These would be a good item if one wore regular boots 100% of the time.
I went back to turning my stirrups and adding endurance stirrups to my saddle with hopes that my knees stop screaming in pain while I ride and afterwards.