I would agree that lunges are a good way to go. When my father had both knees replaced (one at time) one of the things he worked towards was lunges. This was after he was healed up and at the end of his rehab when it was safe to do so but they really wanted to get to them.

I'm having a strange knee issue that I posted about in another thread and I am going to use lunges to see if it helps.

Very good suggestion 0311.