We had a demo at one of our state rondies about just your topic. I think Trapper Art was one of the demonstrators. His problem was not the kneeling so much as it was getting down and back up again. However, there was one fella who found a way to stand and make his sets. If you have two whole legs, you basically start out with your feet as far apart as physically possible and bend over from there. This, of course, is not done at the spur of the moment, but with conditioning all summer for it. Warm up exercises first followed by sincere stretching movements. Sort of like touching your toes, on steroids! Perhaps a visit with your primary care physician first would be prudent. After several months of conditioning you're now able to at least get closer to the ground. This dude also mentioned longer handled tools, although they are a little clumsier to use. If you have to wear a prosthesis, then some experimenting is in order. Just know your physical limitations, and don't hurt yourself!
"I thought getting old would take longer."