God, I have *GOOD* knees (knock on wood) and even I cringe from one leg exercises.
Honestly... anyone else like this? Ha, *ZERO* interest for me in one leg squats, lunges, etc.!
I've played competitive Tennis since I was 12; as a result my workouts aim to improve not just strength, but balance, agility, flexibility (which is where I typically fail), and explosiveness. I've gotten to the point where I can stand on a fully inflated swedish ball and stay balanced while doing squats. I believe my joints (knees, ankles, hips) have become significantly stronger as a result.
For what it's worth, none of the exercises mentioned in my previous post are that complex/advanced. The TRX one leg squats and the TRX lunges are the only exercises I would recommend instruction before doing by one's self. Walking lunges? Box jumps? Sprints? These are staples in any lower body/body weight/interval workout.