@OldboyII canting a binding is where you lift the “inside” of the binding so instead of the binding foot hole pointing straight up, it’s at an angle. You can twist your foot in rubber bindings to the same effect. When I was on Animals I always noticed I would cant my foot so all my weight was on the outside edge of my foot.
I went the opposite way you did and switched from double Radar Vectors to using a Radar ARTP due to knee pain. I’m missing 60-80% of my meniscus in my left knee. I ski RFF. I noticed both a full binding or a 3/4 boot limits the ability to rotate my heal. So when I get into position for my off side wake crossing, it puts a twisting moment on my left leg. My knee takes the brunt of it and I can feel it twist which makes it unstable. My skiing days were probably coming to and end of it wasn’t for switching out my rear binding. Same as you, I had lots of pain from skiing with double bindings.
My observations from this season are that I could probably go to a rubber rear binding with a lot of flex, like the new HO venom or a wileys) or stick with the ARTP. The ARTP offers the most freedom so I’m sticking with it.
I’m a large supporter of “if something causes pain, you need to stop”. You can try canting your binding but if you still notice any pain, stop. Switch to a different set up and reassess. I won’t go into detail, but I should have switched to a different binding setup 10 years ago due to discomfort and more recently pain.