The outside of my left knee (the left side) clicks whenever I'm bearing weight on it and I bend it more than about 45 degrees. When I touch it, what feels like a bone just above and to the left of the kneecap pops out a little bit. My right knee (which is fine) does something similar but much more subtle and I can't feel it unless I'm actually touching it. I'm not really experiencing pain, but whenever a do a lot of exercise my left knee gets a bit sore or more sore than my right.
A while ago I went to the doctor about my knee, which was painful to kneel on at the time, and was given a physiotherapy regimen to strengthen my inner quadricep muscle, which I have been following off and on since.
I'm worried because I have had trouble with this knee for a while now, and while it has never gotten really bad (although it did get very sore for a few weeks, to the extent that walking up stairs was uncomfortable), it has never really gone back to 100% either.