Calm down.

I had knee pain that got to the point of being in terrible pain just to climb or descend the stairs in my house. It seemed to be 100% correlated to riding my fixed gear, as I had been riding road and mountain bikes for years with zero problems. Then I started riding fixed. Had the bike matched to my road fit. Kept getting worse and worse. (Weird thing though, is it never hurt on the bike...).

So I recently had it converted to single speed, and the knees are steadily getting better. So my theory is that something to do with fixed wasn't working for me for the kind of riding I was doing on it (mostly urban 10 mile commutes). I figure skipping and backpedaling were doing something my knees didn't like. Or the relatively large gear (only 72 inches) for all the starting and stopping in a typical urban ride was too much.

As much as I really miss riding my bike fixed, I need my knees. So unless I'm going on the track, or for long, steady rides, I'll be off fixed for while I'm afraid. (oh yeah, 45 years old here).

Poo, after my biggest ride of the year so far yesterday on the crosscheck, my left knee is feeling a bit off. I think it may be time to take my own advice from upthread and get a pro to look at my bike fit. I had someone set up my Marinoni fg conversion last year and it really helped.

Do your knees ache after sitting in a chair for a while? If so you probably have "runner's knee".

Try icing it for 15 minutes a day, take ibuprofen after biking, and start doing some quad strengthening exercises. If it persists I would have my bike professionally fitted (I would do that first, if I had the money)

yes, definitely. put the brake on, your knees will thank you. my 2 cents for whatever it's worth..

It'd probably be wise to raise your seatpost on an FG slightly higher than a road bike setup for skids and skids.

I dont stretch or any of that stuff, I dont know why either seeing as how I cant remember the last time I could touch my toes, I do however use this stuff:
http://www.manekineko.us/catalog/ima...id_enlarge.jpg
and it makes me feel grrrreat

Was having some problems with anterior knee pain, below the patella. Figured it was because my saddle was too far back, so I moved it forward and placed knee over pedal spindle. Voila! Problem solved.

Fit is crucial.

The only time I get internal knee pain is from too heavy stopping with legs. Resistance for slowing is fine, but stopping, I use hand brake.

Al