Originally Posted by a1penguin

Hahaha. I just got my new bike and it was mail order so some assembly required (attaching handlebars and inserting seat). The geometry of the new bike is VERY similar to the existing bike. I misread the seat height on the older bike and I missed by about 1/2". It was close enough and I did not ride the bikes back to back so I didn't notice. I went on a 20 mile ride and dang my left knee was not happy. Nothing too serious and a longer ride on the old bike the knee was OK. I raised the seat 1/2" and now my knee has stopped complaining.

Who is to say that your bike doesn't have a similar issue? If you want to be biking 30 years from now, I recommend that visiting a physical therapist would be in order. And perhaps a professional bike fit. First, though, is understanding (not guessing!) the cause of your knee issues.

I stopped riding a decade or so ago because of knee problems, so I live in fear of future knee problems. I will not hesitate to seek medical professional if knee problems recur.