I used Voltaren on my thumb for months. It lasts a few hours but the NSAID aspect of it seems to linger, as it should. I think personally Voltaren gel is not for deep joint pain. But on the hands it is a good treatment. Therefore, depending on the diagnosis, it might be good for feet as well. Hips and
shoulders are tough to reach with a topical.
This is all, everything I say, empirical opinion. I'm not a doc and don't know
JS about anatomy.
One thing I didn't mention is ultrasound. We are not supposed to be able to buy those over the counter. Order one from a foreign country if you can find a recommendation. You never know about what you can't see or measure. Small units capable of treating a hand joint are not the big block 454cc models the chiropractor uses.