I'll answer your second question first. YUP! And maybe even more! You'll get there. Just take your time.
As for your knee hurting there is obviously a lot of things I don't know about your knee (as well as body build, age, general fitness, weight, etc which can all play in there) But I do deal with some knee pains myself as here are some things that help my knees that I can see would hurt your any if you wanted to give them a try.
1) I have to keep my hamstrings stretched a bit. If I let them get really tight it makes my knee hurt.
2) I have to keep my IT band rolled out (I use a foam roller. Hurts like hell for the first week or so and then it starts to not hurt while rolling so much!) or my left knee starts popping.
3) Sometimes if my knee is just not quite right I can lock my knee back so that my kneecap is loose and then use my hand to just wiggle my knee cap up and down and side to side a bit and it feels better. Don't know exactly what is up with that.
And finally if you can't figure it out I recommend a trip to your doctor and/or a physical therapist. I went to my doc (for the knee popping), she sent m to the PT, I went to one session with the PT who gave me some exercises, stretches, foam rolling, etc and in about 10 days my knee quit popping. So it's worth a try!