TejanoTrackie 

I'm 64 and have been riding and racing fixed for 35+ years. I use backpedalling as my only way of stopping on the track and normal method on the road. I have never had serious knee problems, not even tendonitis. My gearing on the road varies from 62 to 71 gear inches. My conclusion is that slowing down and stopping a FG by back pedalling is not inherently bad for your knees. I use a front brake only for emergency situations when I need to stop very quickly or to control maximum rpms when descending a steep and or long downhill.