How old is your dog? A good general rule of thumb for how long a pup can walk on a leash (without break) is 5 minutes for every month of age beginning at 2. So 5 minutes for a 2 month, 10 minutes for a 3 month old, and so on.
If you happen to have the sort of pup that insists upon stopping every few metres to investigate the world and smell the roses - that's a good thing and would probably allow you to keep going a bit longer. The problem with leash walks or jogging, of course, being that it's continuous - and that means continuous pounding on the soft and vulnerable joints. When it's off leash AND the pup is able to take lots of little breaks as they choose, then that doesn't really apply - they can safely run and play to their heart's content.
So IF your pup takes all those sorts of little breaks and just plops himself down for a little rest now and then during your walks, you could probably assume some of the off-leash benefit there. Most don't though

They try to keep up with or outpace us. So it's up to us then to ensure that the walk is of appropriate duration and minimise the risk of any damage. When they're little there's nothing to stop us from picking them up and carrying them for a bit, on those occassions we want to go further