Thanks for all these suggestions. Well two years into it i've still not solved my PFS problem. I can relate to the symptoms & frustrations listed in your posts all too well.
I get knee pain usually 3 hrs into a road ride. Initally I feel a sort of tugging or tightness at the very top of the calf (maybe the gastrocnemious). At this stage it's not too painful, but if I continue to cycle for 10-20 minutes it then quickly escalates into very severe knee pain on the lateral side of the knee. The knee becomes red and swollen and i cannot continue cycling. In fact, I can barely walk. If I stand up in the saddle the pain lessens somewhat. But I cannot lower my body weight on that leg at all . Climbing & descending stairs is too painful for 10 hrs or so. And yet, 24-48 hrs later im almost pain-free and can cycle again (although im not doing that as rountine).
In general, I'm always getting the "cinema-sign" symptom of an aching knee-cap after prolonged sitting or driving. I've also noticed that the vmo on the problem leg, although still of a fair size, is weaker and doesn't fire as strongly as the other vmo muscle. MRI scan showed a slightly lateral tilt of my patellar. Im still limited in the amount of cycling I can do. I did do one 80 mile road-ride this summer and got away with it. I used to do a ride like that at least once a week.
Some conclusions i've made:
* The ball and squat excercise recommended by kennf, which i've started doing recently, seems to be improving things slightly.
* McConnell taping of the knee seems to help a little too.
* I stretch and stretch and am now the most flexible man in Britain. Probably for that reason I don't find stretching to help any further. But my calves are still tight I reckon.
* I find mountain biking to be easier on the knees, probably due to the lower gears and the lower rpms on the descents.
* Resting definitely makes the knee pain worse.
* Tried all the excercises and I still cannot get my problem vmo to function correctly i.e fire and flex like the normal vmo.
* The cinema sign symptom seems to be a good indicator of the severity of the PFS, which seems to vary over time but never go.
* Some physios are excellent. Some are a total waste of space. If you see one make sure they're a sports physio who actually does some sport.