Imbalance is right on track, no pun intended...
I'm not a doctor either but I'll relate my knee "issues". Both of my knees crunch like celery and, up until a month or so ago, both knees clicked/popped rather noisily. I finally got fed up with some pain in the left knee and went to see to the doc where he me told I have a thing called 'chondromalacia' which is basically a degradation of the cartilage under the kneecap. Oh yea I also have some scar tissue under the left patellar tendon in front of my knee to. Nifty eh?
After a month of PT working my left knee, it doesn't pop nearly as much because the VMO muscle that makes up part of the quad is pulling the kneecap back in it's track more normally now. The VMO is that muscle that's just to the inside of the center line down your quad, right above the kneecap and sort of sticks up by itself when you're pushing down and the one that usually burns first to. Yea that one. That's the imbalance part because the quad is made up of 4 separate muscles and the VMO has to 'fire' first when you clench your quad. Am I listening the therapist or what?
Anyway, long story a bit shorter, you might have a/both kneecap(s) tracking a bit out of the groove it's supposed to ride in but not as severely as mine do. Here's a link to a description:
http://www.arthroscopy.com/sp05032.htm. With my knee, the doc will almost surely have to go in and scrape the cartilage on the bottom of the kneecap to clean it up. Sounds lovely doesn't it? I just hope I can get through the summer without too much more pain.
Oh and that clicking sound, at least in my case, dunno about yours obviously, is the kneecap tracking so far out of the groove that it actually pops over the edge of the femur.
Don't want to scare you because my symptoms are pretty far along but you might want to have a doc and/physical therapist look at your knees so you can avoid future problems.
Questions: are either of you guys flat-footed or over pronaters (your instep rolls in noticeably)?