As fantastic as these words of wisdom are, they are unfortunately a little off the mark. By the sound of it cookie has injuried his knee in a certain way which has likely caused knee swelling and thus restricted, the mentioned, Vastus Medialis and could have caused severe muscle loss. The problem is that in the future an imbalance between the 4 quads muscles this can in turn cause various problems which can be very painful.
Treatment would depend on how serious it is and the most extreme end of the scale is biofeedback training which basically allows you to train the VM without training the other quads anywhere near as much so that it can effectively catch the others up. At the other end of the scale ther are things like simply emphasising certain ways of doing lunges, step downs, hack squats and various other things. Which are probably exactly what was recommended to you :? . If you want to make some big improvements I would suggest that you find a very good physio in your region, I can recommend a fantastic one in south wales if you want, who I saw for a while when I had to have surgery on my ankle.
If this is not treated properly you can hold on to the injury for a lot longer than you should and can also be why you here so many people say things like "oh thats my bad leg from when I used to play rugby" its probably, though not in all cases, because they didn't treat it correctly.
Hope you get better soon