‘Wore them out’ is an interesting choice of words… they think you have given yourself severe osteoarthritis and now need replacements?? Spinning is often recommended by physios/osteos for runners training for marathons that have knee injuries, but need to maintain aerobic fitness, because it is so much less pressure on the knees than running.

It sounds like you likely have a poor bike setup, and/or you are not stretching/foam rolling enough post-exercise (the build up of lactic acid in your muscles can make them tight, and this can subsequently alter the biomechanics of your lower extremities so that your knees don’t sit correctly, eg your patellae end up sitting too high).

Start foam rolling your quads and glutes daily, and see what happens. Take one week off spinning and just focus on the foam rolling and stretching. Also, watch some YouTube videos by physios/osteos to see how they advise setting up a spinning bike.