Up until the point that you blow your knee out from repetitive stress. (happens to 40-60% of avid cyclists eventually)
It got so bad I could only use one leg to go up stairs or stand up from a chair. The cartilage would not heal until I took platelet rich plasma treatment a couple of years ago, and it's been slowly getting better since. I'm hoping I'll be able to get back on the bike again eventually.
Sure, cyclists get twinges now and again but nowhere near as many as runners or hikers..
In my cycling days I used to sometimes get a pain like toothache on the outside of my left knee joint when pedalling but luckily it wasn't serious.
Incidentally I haven't been on a bike for about 12 years, i just drifted away from it and became a couch potato, for examp the summer weather here has been beautiful for weeks but I haven't had the slightest inclination to saddle up, I've been chilling and watching my boxed DVD set of 'The Outer Limits'..