I'm sure dogs have their aches and pains just as we do, but they're more stoic as a species than we are. My dogs have done some things that had to be wicked painful, but they just kept on going like it was no big deal. I would've stopped what I was doing to scream.
So considering my dogs' tolerance for pain, if there's a day when they're visibly not feeling well, I give them as long as they need to rest and keep a watchful eye on them.