I'm 14, and I ride daily as long as I'm feeling up to it, but I'm not in good health and I have the same problems, although what takes the shock depends on the discipline I'm riding. Jumping, it's horrible in my knees and kinda in my ankles; dressage is pretty bad on my hips; western, especially gaming, hits my lower back pretty hard; and it also varies on the horse and how much I'm riding. The day after a trial, I'm stuck on the couch. But the one thing that I feel actually helps is taking a couple ibuprofen first thing in the morning, then taking a cold shower. About an hour after the shower, I rub horse linament over the areas that are sore. I also wrap my ankles and knees if that's what is sore so that it just has extra support and they don't hurt so bad to walk on, and I have a back brace for the extreme days. Hope these help, I've had to adapt cause there's no way this stuff is going to take me outa the saddle!
Eventing: the only sport where you wear your medical information strapped to your arm.