I'm also part of the bad knees club!
I'm only 23 years old but my right knee often doesn't feel right. Today when I was running it was sore for the first 5 minutes and then it felt better during the rest of my run. Afterwards it was popping and felt like it was grinding though.
I'm going to have to try the squatting exercise with the ball as well as the leg lifts.
I know I shouldn't run but I have to because I know if I stop running I won't exercise so I will have to concentrate on strengthing my leg muscles more.
Hopefully I won't one day be destined for a knee replacement like a few other family members :S