Just had to cut my ride short due to a funky feeling going down the center of my left knee. No pain to speak of, but more a warning to cool it off a bit. I got this feeling in my knee toward the end of my last ride. Here's a list of possible causes that I can think of off the top of my head:
1. Frame is too small. I'm 6'3" w/ a 34-35" inseam. From the center of my BB to the center of my top tube, my frame measures 56cm. I know that's too small, but I'm poor and it was cheap.
2. Seat not back far enough. I have my saddle as far back as I can get it. Even so, I feel much better when my butt's hanging off the end.
3. Over training. I could be putting too much too soon. I've been kinda sedentary for a while due to work and have just now begun to get more active (w/in the last 2 months). I don't think I've done a good job of easing myself into this. I did the same thing with running. Shin splints galore.
Anyone care to comment? I'm riding single speed right now so I kinda have to mash it up hills. That could also be something to consider. I'm gonig to go look up knee exercises after I post this, but does anyone here have a favorite they care to share? Is there anything I'm missing and should be taking into consideration?
All of the things you have named will most likely contribute to knee pain. If it is overtraining, take 5-7 days off and ease back into things. Don't forget to stretch IT band, hamstrings, quads, groins, glutes, and calves once or twice a day. Frame size and fit are also a big deal for knee problems. I had tendonitis in my left knee, and i had to get re-fit to my bike and take a week off while incorporating stetching and icing to get ride of it. Question, does the funky feeling feel sort of like momentary "twang" (sorry for the crappy description, best i could think of), kind of like when you try and walk and a muscle is really tight and you get that wierd, tingle feeling that only lasts momentarily when the joint is bearing load? also, does it happen on any certain part of your pedal stroke, or any time when you aren't on the bike, like stairs? I would try icing, stretching, some rest, and everything you can do to get fit to your bike (this should include going to a bigger frame when you have the cash). If the weird feeling turns into a pain, then go to a doctor. Also, if you are riding with clipless, make sure the cleats are positioned properly (if the right knee isn't bothering you, use that cleat as a template)