It may be that the lunge motion is causing you pain in your knees.  I have bad knees and lunges are often difficult for my knees.  You may want to stick to squats or work on modifying your form in lunges.  You have to make sure your knees line up with your toes when you do your lunges. 

Weight training is good to mix with running, you just need to make sure you don't over do.  Listen to your body, if you are having pain, modify or take some time off.  If you are building up to a 5K and you have not run before, make sure you are taking plenty of walk breaks as you need it.  After I completed couch to 5K, I found that running continuously was not good for my knees, so I decided to change to the Jeff Galloway method and I encorporate walk breaks throughout my runs.  It has made all the difference in the length of time I can run and the way I feel afterward. 

Good luck to you!

Kendra

Hi momma.  I'm a newbie too that has been dealing with knee pain too.  My shoes were well past replacement time at 2 years old.  New shoes were cheaper than an MRI.  I spent 2 hours at a running store, drove 30 minutes across town to another that had my size, and exchanged them for a different model 2 weeks later.  My knee pain is 70% better.  Treadmill running can cause knee pain too.  Make sure it is cushioned with a forgiving deck and keep the incline below 3%.  I do a run walk on the treadmill at 4mph and 6.5 mph for 30 minutes 2 or 3 times a week.  Weight training or squats on weak knees are dangerous so be careful.  Spin classes are what works for me.  Sprinting, hill climbing, up down hover...really blasts the quads and hamstrings which helps to support and stabilze the knees.  Also, our bodies are lazy and adjust to the same routine so you need to switch it up once in awhile.  Lastly, time and patience!  I spent decades creating this weak mass of jello so fixing it overnight isn't going to happen.  Good luck and keep going.

I'm still a walk/runner and probably always will be from 30 years of smoking:(  I just finished my 3rd 5K Sat. (started running this year) and ran the first mile, run/walk after that.  One of the race monitors trotted up and asked if I was ok, I think (headphones blasting some Rush).  I gave him a thumbs up and ran a little faster.  I'm a huffer...very noisy runner!  My knee pain is almost gone.  I don't see myself ever doing a marathon, but maybe a half someday.  Good luck with your's!  Btw, I grew up around LR.  Loved the western part.