Welcome. Perhaps some modest home exercise equipment and training would extend your capabilities. May I remark that there are seniors in their eighties and nineties who work hard at getting and staying fit so they can participate in marathons and other competitive athletic events? There's one lady, (who made it to 95) who accumulated hundreds of gold medals doing this (there's a good book about her: What Makes Olga Run?).
My point is that our bodies (at least our muscles and to a slower extent, our ligaments and bones) often have enormous potential for improvement and strengthening. Or not. Perhaps it would help to read about some athelitic success stories including those with cerebral palsy. (some examples are at: http://cerebralpalsy.org/inspiration/athletes/ )
Hi I'm new to this site and came across your post. I'm 45 now and like you I am finding it hard with the pain in my legs, I know people harp on about exercise and everything but I find it makes me worse, even the physio's here don't know how to help (uk based) so I'm under pain specialists in London but still in pain. If you want to talk just post and I will get back to you ASAP, if you have found some help with the pain please let me know