Coming off a step good leg first puts the job of keeping your body up on your "worse" knee. My PT in rehab (she was really good) explained that the good knee has the stronger quad. It's why we choose it to be the good knee (with bilaterals, we designate one knee as our "good" knee for things like stairs, using the cane, etc.), because it is already stronger. Eventually part of rehab is to work on getting that "worse" knee stronger.
One way I did it at home was to start going down single steps and curbs using my good knee first and letting the worse knee do the stabilizing. Same with going up, I'd start with the worse knee for that. It feels awkward at first. What eventually happens, though, is the quad does become stronger. I've learned to trust my worse knee now and use it more, and both knees have become much more stable when doing stairs.
Actually using the knee does wonders for gaining ROM and strength.