I have knee issues as well and recently starting spinning. The knee complains sometimes, so I have taken it slow. My legs are strong from finishing STS for the 2nd time this month, but still had to build up in time and the gears I use. I don't have Ride, but do have Cathe's Cycle Max and I have had to back off some in how much I stand and the gears used.
But can I tell it has been good for me, for legs and cardio workout, I can tell improvements in both. I am working towards enjoying mountain biking this summer by already having some biking conditioning before I am able to bike outside.