Cycling activates a lot of muscles,upperleg,hips,calves so the exertion is divided among a large group of muscles and that increases the effect of muscle-development,of course a lot of cycling has some effect on your legmuscles and make your legs look bigger but is not effective in decreasing kneeproblems,on the contrary.
I also cycle a lot.
But developing muscles by isolating one special group for instance leg-extensions for the quadriceps or leg-curls for the hamstings is quiet
another ball-game and the solution for kneeproblems.
If you use a lot of weight (not in the beginning of course) practising these exercises for a long time
you are beginning to develop legs like a body-builder does.
That is not the intention in your case i think.
If you don't use to much weight it is an excellent way to develop your
Q's and H's so they the muscles-group that really protect your knees.
I am an addicted runner, run al lot on concrete, am 38 years old
and have no problems with my knees at all (hope it stays that way).
I have got this advice from my physiologist and hope you can do something with it.
Cycling won't solve your problem.
DON'T WASTE YOUR MONEY ON INTERNET HEIGHT SCAMS - 99% OF THEM DON'T WORK - - YOGA STYLE STRETCHING, KICKING, HANGING & EXERCISES ARE THE ONLY WAY TO INCREASE YOUR HEIGHT IF YOU ARE AN ADULT (OR RISKY, EXPENSIVE SURGERY!) WE'VE RESEARCHED EVERYTHING AND CAN TELL YOU WHAT'S A SCAM AND WHAT IS WORTH CONSIDERING. IF THESE SO CALLED "MIRACLE" PRODUCTS ADVERTISED BY THESE INTERNET COMPANIES WORKED, THEY WOULD BE ON BILLBOARDS, TELEVISION AND THE RADIO AND WOULD BE KNOWN WORLDWIDE!!!!!