When I was younger (through I would say 50) it was primarily my right leg. As I got older it spread and I got concerned. I was told that as you get older the polio begins to affect again. It's called post polio syndrome and simply caused more loss of strength. Now at near 70 it's nearly impossible to walk more than 100 yrds and that with the support of a cane or staff and working on my feet impossible after about 10 minutes. I do all my gardening on my rear end crawling on the ground. It's not pretty but it gets the job done. In the green house and in my shop I have a stool on wheels.
Now I am truly filled with admiration. My garden went to Hellengone last year because I couldn't weed or even adequately put down mulch. I told my dearest dear of a husband that we should just let Tennessee take it over (all 70 square feet) as a Wilderness Area. Sounds more respectable than Weedpatch.
I should try your butt crawling technique. I guess what I'll be doing this winter is reinforcing the seats AND knees of my pants.