Cycling will improve your leg strength. Normally the larger leg muscles at the top develop first, over time the development will work its way down to the muscles above the knee. Normally this takes me about a year or two of heavy duty cycling.
I have a personal story to share. I tore my ACL playing basketball at the age of twenty. I had stability issues on my left side for years. The problems went away after I biked across the country in my young 20's. I developed so much dense muscle mass I did not need an ACL to hold my leg together. Then in my late 20's I stopped cycling and started fighting. I ended up tearing both meniscuses in my left knee. The inside meniscus became stable over the years, however the outside continued to tear every few years. This past year I started working at Jimmy John's as a bicycle delivery person. My knee has strengthened amazingly, and I plan to continue working as a bicycle delivery rider to keep my knee out of trouble.
Author: Dr. Yan Lyansky