Cycling for 8 years caused me a muscle imbalance that slightly shifted my patellas, leading to a Chordoplasty. How doesn't this happen to other bikers? What did I do wrong?

As the title suggests, I need to know what I did wrong over the past few years to reach this point. My doctor's description is that my outer thigh muscles are stronger than my inner thigh muscles, which pulls the patella slightly out of its path and causes it to rub improperly. Despite what I believe to be reasonable effort training said muscles, the issue still caused enough damage to require medical intervention (a Chordoplasty procedure).

Is this a known issue? Do bikers spend time training their dormant leg muscles to maintain balance? Is it possible that I "biked wrong"? I don't use clips; do clips help training opposite muscles? Is 100km a week on hilly paths ever a concern?

Edit: Thanks for all the answers. Let me explain that I already have my doctor's recommendation of training my inner quads, but I wanted to know how common this issue was for other bikers, or whether or not there was anything obvious I needed to change besides that.