Knee strengthening for running?

I am training again for the first 5K this year on May 29th.  Did my first ever last year and WILL beat my time.  I did a 11:42 and am determined to do a 10 min mile this year and better.  However my knees are hurting a bit - I read it may be because I have weak leg muscles?  I have one knee without an ACL from a skiing accident many years ago.  I am at goal weight so the weight issue shouldn't be the problem.  Any great exercises to strengthen the muscles around the knees or leading to the knees to make running more comfortable?

When I went to PT for my knee pain they had me do a few things.   I did some work on a machine that simulated squats but you were lying on your back.  I also did lots of balance work which helped the hips and ankle also.   I like to do leg extensions at the gym.  That supposedly keeps your knee cap in place when you run.  Lastly, I would ice it after every run. You could do a search for knee therapy or something like that to get an idea what the pictures may look like.

Thanks Scott - I will check it out.  I am doing lunges but never know if they are helpful.  I guess I will continue them and we'll see as time progresses. 

One other suggestion is to spend some serious time on a bike with good resistance.  Good strengthening without the pounding. Linn